--- title: "Introduction to Linux CLI" description: "Introduction to Linux command-line interface CLI, Linux is a Unix-like computer operating system assembled under the model of free and open-source software development and distribution." author: "Mohammad Abu Mattar" canonical: https://mkabumattar.com/blog/post/introduction-to-linux-cli --- # Introduction to Linux CLI ## Introduction The Linux operating system family is a group of free and open-source Unix systems. They consist of Red Hat, Arch Linux, Ubuntu, Debian, openSUSE, and Fedora. You must utilize a shell when using Linux, an application that allows you access to the system's features. The majority of Linux distributions have a graphical user interface (GUI), which makes them user-friendly for beginners. I advise using the command-line interface (CLI), as it is speedier and gives you more control. By putting commands into the CLI, tasks that take many steps on the GUI may be completed in a matter of seconds. ## What Is a Linux Command? An application or tool that runs on the CLI, a console that communicates with the system via text and processes, is known as a Linux command. It resembles Windows' Command Prompt program in many ways. By hitting Enter at the end of the line, Linux commands are run on the terminal. You may use commands to carry out a range of operations, including managing users, installing packages, and manipulating files. The general syntax of a Linux command is as follows: **CommandName [flag(s)] [parameter(s)]** - **CommandName** is the name of the command you want to run. - **Flag(s)** are optional arguments that modify the behavior of the command. - **Parameter(s)** are required arguments that specify the command's input. Remember that case affects the syntax of every Linux command. ## File Management Every system administrator should be familiar with the very basic commands listed in this section. This collection of Linux commands for managing files is undoubtedly incomplete, but it can serve as a starting point and cover the majority of simple to complicated situations. ### `pwd` The `pwd` command is used to print the current working directory. The working directory is the directory you are currently in. The output of the `pwd` command is the path to the working directory. ```shell # Print the current working directory pwd ``` #### `pwd` Flags
- `-L` - If the current working directory is a symbolic link, print the path of the symbolic link. - `-P` - If the current working directory is a symbolic link, print the path of the symbolic link's target. ```shell # Print the current working directory pwd -L # Print the current working directory pwd -P ```
### `ls` `ls` is A system's files and directories are listed using the `ls` command. It will display the contents of the current working directory when run without a flag or argument. ```shell # List the contents of the current working directory ls ``` #### `ls` Flags
- `-a` - List all files, including hidden files. - `-l` - List files in long format. - `-h` - List files in human-readable format. - `-r` - List files in reverse order. - `-t` - List files by the time they were last modified. ```shell # List all files, including hidden files ls -a # List files in long format ls -l # List files in human-readable format ls -h # List files in reverse order ls -r # List files by the time they were last modified ls -t ```
### `cd` The `cd` command is used to change the current working directory. It takes a directory as an argument. The output of the `cd` command is the new working directory. ```shell # Change the current working directory to the home directory cd ~ ``` ### `mkdir` The `mkdir` command is used to create a new directory. It takes a directory name as an argument. The output of the `mkdir` command is the newly created directory. ```shell # Create a new directory named "new-directory" mkdir new-directory ``` #### `mkdir` Flags
- `-p` - Create parent directories as needed. ```shell # Create a new directory named "new-directory" and its parent directories mkdir -p new-directory ```
### `touch` The `touch` command is used to create a new file. It takes a file name as an argument. The output of the `touch` command is the newly created file. ```shell # Create a new file named "new-file" touch new-file ``` #### `touch` Flags
- `-a` - Change the access time of the file. - `-m` - Change the modification time of the file. - `-t` - Change the access and modification times of the file. ```shell # Change the access time of the file touch -a new-file # Change the modification time of the file touch -m new-file # Change the access and modification times of the file touch -t new-file ```
### `cp` The `cp` command is used to copy files and directories. It takes the source and destination as arguments. The output of the `cp` command is the copied file or directory. ```shell # Copy the file "file" to the directory "directory" cp file directory ``` #### `cp` Flags
- `-r` - Copy directories recursively. ```shell # Copy the directory "directory" to the directory "new-directory" cp -r directory new-directory ```
### `mv` The `mv` command is used to move files and directories. It takes the source and destination as arguments. The output of the `mv` command is the moved file or directory. ```shell # Move the file "file" to the directory "directory" mv file directory ``` #### `mv` Flags
- `-i` - Prompt before overwriting an existing file. - `-f` - Force the move of a file, even if it already exists. - `-u` - Move a file only if the source file is newer than the destination file. ```shell # Move the file "file" to the directory "directory" and prompt before overwriting an existing file mv -i file directory # Move the file "file" to the directory "directory" and force the move of a file, even if it already exists mv -f file directory # Move the file "file" to the directory "directory" and move a file only if the source file is newer than the destination file mv -u file directory ```
### `rm` The `rm` command is used to remove files and directories. It takes the file or directory as an argument. The output of the `rm` command is the removed file or directory. ```shell # Remove the file "file" rm file ``` #### `rm` Flags
- `-r` - Remove directories and their contents recursively. - `-f` - Force remove files without prompting for confirmation. ```shell # Remove the directory "directory" and its contents recursively rm -r directory # Remove the file "file" without prompting for confirmation rm -f file ```
### `rmdir` The `rmdir` command is used to remove empty directories. It takes the directory as an argument. The output of the `rmdir` command is the removed directory. ```shell # Remove the directory "directory" rmdir directory ``` #### `rmdir` Flags
- `-p` - Remove parent directories as needed. ```shell # Remove the directory "directory" and its parent directories rmdir -p directory ```
### `cat` The `cat` command is used to display the contents of a file. It takes a file as an argument. The output of the `cat` command is the contents of the specified file. ```shell # Display the contents of the file "file" cat file ``` #### `cat` Flags
- `-n` - Number all output lines. ```shell # Display the contents of the file "file" and number all output lines cat -n file ```
### `more` The `more` command is used to display the contents of a file. It takes a file as an argument. The output of the `more` command is the contents of the specified file. ```shell # Display the contents of the file "file" more file ``` #### `more` Flags
- `-d` - Display the contents of the file "file" and number all output lines. ```shell # Display the contents of the file "file" and number all output lines more -d file ```
### `less` The `less` command is used to display the contents of a file. It takes a file as an argument. The output of the `less` command is the contents of the specified file. ```shell # Display the contents of the file "file" less file ``` #### `less` Flags
- `-N` - Display the contents of the file "file" and number all output lines. ```shell # Display the contents of the file "file" and number all output lines less -N file ```
### `head` The `head` command is used to display the first 10 lines of a file. It takes a file as an argument. The output of the `head` command is the first 10 lines of the specified file. ```shell # Display the first 10 lines of the file "file" head file ``` #### `head` Flags
- `-n` - Display the first n lines of the file "file". ```shell # Display the first 5 lines of the file "file" head -n 5 file ```
### `tail` The `tail` command is used to display the last 10 lines of a file. It takes a file as an argument. The output of the `tail` command is the last 10 lines of the specified file. ```shell # Display the last 10 lines of the file "file" tail file ``` #### `tail` Flags
- `-n` - Display the last n lines of the file "file". ```shell # Display the last 5 lines of the file "file" tail -n 5 file ```
## Finding files and directories The find command will be used the majority of the time to locate files and folders. But I also enjoy the which command since it provides the binary's path, which is necessary on several occasions when we must run a binary with a complete PATH. ### `find` The `find` command is used to find files and directories. It takes a directory as an argument. The output of the `find` command is the files and directories that match the specified criteria. ```shell # Find all files and directories in the current directory find . ``` #### `find` Flags
- `-name` - Find files and directories with the specified name. - `-type` - Find files and directories of the specified type. - `-size` - Find files and directories of the specified size. - `-mtime` - Find files and directories that have been modified in the specified number of days. - `-exec` - Execute the specified command on the found files and directories. ```shell # Find all files and directories in the current directory with the name "file" find . -name file # Find all files and directories in the current directory of the type "file" find . -type file # Find all files and directories in the current directory of the size "1M" find . -size 1M # Find all files and directories in the current directory that have been modified in the last 5 days find . -mtime 5 # Find all files and directories in the current directory with the name "file" and execute the command "ls" on them find . -name file -exec ls {} \; ```
### `locate` The `locate` command is used to find files and directories. It takes a file or directory name as an argument. The output of the `locate` command is the files and directories that match the specified criteria. ```shell # Find all files and directories in the current directory with the name "file" locate file ``` #### `locate` Flags
- `-i` - Find files and directories with the specified name, ignoring case. ```shell # Find all files and directories in the current directory with the name "file" ignoring case locate -i file ```
### `which` The `which` command is used to find the location of a command. It takes a command as an argument. The output of the `which` command is the location of the specified command. ```shell # Find the location of the command "command" which command ``` #### `which` Flags
- `-a` - Find all locations of the specified command. - `-s` - Find the location of the specified command and return a status code of 0 if the command is found and 1 if the command is not found. ```shell # Find all locations of the command "command" which -a command # Find the location of the command "command" and return a status code of 0 if the command is found and 1 if the command is not found which -s command ```
### `whereis` The `whereis` command is used to find the location of a command. It takes a command as an argument. The output of the `whereis` command is the location of the specified command. ```shell # Find the location of the command "command" whereis command ``` #### `whereis` Flags
- `-b` - Find the location of the specified command and return a status code of 0 if the command is found and 1 if the command is not found. ```shell # Find the location of the command "command" and return a status code of 0 if the command is found and 1 if the command is not found whereis -b command ```
## Check User Information These are a few of the commands we employ to verify the details of the most recent person to log in, as well as a few others to obtain further information regarding an existing user. ### `whoami` The `whoami` command is used to display the current user. It takes no arguments. The output of the `whoami` command is the current user. ```shell # Display the current user whoami ``` #### `whoami` Flags
- `-u` - Display the current user and return a status code of 0 if the user is found and 1 if the user is not found. ```shell # Display the current user and return a status code of 0 if the user is found and 1 if the user is not found whoami -u ```
### `who` The `who` command is used to display the current users. It takes no arguments. The output of the `who` command is the current users. ```shell # Display the current users who ``` #### `who` Flags
- `-u` - Display the current users and return a status code of 0 if the users are found and 1 if the users are not found. ```shell # Display the current users and return a status code of 0 if the users are found and 1 if the users are not found who -u ```
### `w` The `w` command is used to display the current users. It takes no arguments. The output of the `w` command is the current users. ```shell # Display the current users w ``` #### `w` Flags
- `-u` - Display the current users and return a status code of 0 if the users are found and 1 if the users are not found. ```shell # Display the current users and return a status code of 0 if the users are found and 1 if the users are not found w -u ```
### `id` The `id` command is used to display the current user. It takes no arguments. The output of the `id` command is the current user. ```shell # Display the current user id ``` #### `id` Flags
- `-u` - Display the current user and return a status code of 0 if the user is found and 1 if the user is not found. ```shell # Display the current user and return a status code of 0 if the user is found and 1 if the user is not found id -u ```
### `groups` The `groups` command is used to display the current user's groups. It takes no arguments. The output of the `groups` command is the current user's groups. ```shell # Display the current user's groups groups ``` ## Managing Users and Groups These are some of the fundamental Linux commands for managing users, including adding, editing, and removing individuals or groups. ### `useradd` The `useradd` command is used to add a user. It takes a username as an argument. The output of the `useradd` command is the user that was added. ```shell # Add a user with the username "user" useradd user ``` #### `useradd` Flags
- `-c` - Add a user with the specified comment. - `-d` - Add a user with the specified home directory. - `-g` - Add a user with the specified primary group. - `-G` - Add a user with the specified supplementary groups. - `-m` - Add a user with the specified home directory. - `-s` - Add a user with the specified shell. - `-u` - Add a user with the specified user ID. ```shell # Add a user with the username "user" and comment "comment" useradd -c "comment" user # Add a user with the username "user" and home directory "/home/user" useradd -d /home/user user # Add a user with the username "user" and primary group "group" useradd -g group user # Add a user with the username "user" and supplementary groups "group1", "group2", and "group3" useradd -G group1,group2,group3 user # Add a user with the username "user" and home directory "/home/user" useradd -m /home/user user # Add a user with the username "user" and shell "/bin/sh" useradd -s /bin/sh user # Add a user with the username "user" and user ID "1000" useradd -u 1000 user ```
### `userdel` The `userdel` command is used to delete a user. It takes a username as an argument. The output of the `userdel` command is the user that was deleted. ```shell # Delete a user with the username "user" userdel user ``` #### `userdel` Flags
- `-r` - Delete a user with the specified home directory. ```shell # Delete a user with the username "user" and home directory "/home/user" userdel -r /home/user user ```
### `usermod` The `usermod` command is used to modify a user. It takes a username as an argument. The output of the `usermod` command is the user that was modified. ```shell # Modify a user with the username "user" usermod user ``` #### `usermod` Flags
- `-c` - Modify a user with the specified comment. - `-d` - Modify a user with the specified home directory. - `-e` - Modify a user with the specified expiration date. - `-g` - Modify a user with the specified primary group. - `-G` - Modify a user with the specified supplementary groups. - `-l` - Modify a user with the specified username. - `-m` - Modify a user with the specified home directory. - `-s` - Modify a user with the specified shell. - `-u` - Modify a user with the specified user ID. ```shell # Modify a user with the username "user" and comment "comment" usermod -c "comment" user # Modify a user with the username "user" and home directory "/home/user" usermod -d /home/user user # Modify a user with the username "user" and expiration date "2023-01-01" usermod -e 2023-01-01 user # Modify a user with the username "user" and primary group "group" usermod -g group user # Modify a user with the username "user" and supplementary groups "group1", "group2", and "group3" usermod -G group1,group2,group3 user # Modify a user with the username "user" and username "user2" usermod -l user2 user # Modify a user with the username "user" and home directory "/home/user" usermod -m /home/user user # Modify a user with the username "user" and shell "/bin/sh" usermod -s /bin/sh user # Modify a user with the username "user" and user ID "1000" usermod -u 1000 user ```
### `passwd` The `passwd` command is used to change a user's password. It takes a username as an argument. The output of the `passwd` command is the user's password that was changed. ```shell # Change a user's password with the username "user" passwd user ``` #### `passwd` Flags
- `-d` - Change a user's password with the specified username and delete the password. - `-e` - Change a user's password with the specified username and expire the password. - `-l` - Change a user's password with the specified username and lock the password. - `-u` - Change a user's password with the specified username and unlock the password. ```shell # Change a user's password with the username "user" and delete the password passwd -d user # Change a user's password with the username "user" and expire the password passwd -e user # Change a user's password with the username "user" and lock the password passwd -l user # Change a user's password with the username "user" and unlock the password passwd -u user ```
### `groupadd` The `groupadd` command is used to add a group. It takes a group name as an argument. The output of the `groupadd` command is the group that was added. ```shell # Add a group with the group name "group" groupadd group ``` #### `groupadd` Flags
- `-g` - Add a group with the specified group ID. - `-r` - Add a group with the specified system group. - `-f` - Add a group with the specified force. ```shell # Add a group with the group name "group" and group ID "1000" groupadd -g 1000 group # Add a group with the group name "group" and system group groupadd -r group # Add a group with the group name "group" and force groupadd -f group ```
### `groupdel` The `groupdel` command is used to delete a group. It takes a group name as an argument. The output of the `groupdel` command is the group that was deleted. ```shell # Delete a group with the group name "group" groupdel group ``` #### `groupdel` Flags
- `-f` - Delete a group with the specified force. ```shell # Delete a group with the group name "group" and force groupdel -f group ```
### `groupmod` The `groupmod` command is used to modify a group. It takes a group name as an argument. The output of the `groupmod` command is the group that was modified. ```shell # Modify a group with the group name "group" groupmod group ``` #### `groupmod` Flags
- `-g` - Modify a group with the specified group ID. - `-n` - Modify a group with the specified group name. ```shell # Modify a group with the group name "group" and group ID "1000" groupmod -g 1000 group # Modify a group with the group name "group" and group name "group2" groupmod -n group2 group ```
## Managing Permissions I have simply addressed the fundamental commands that we use to assign, change, and remove rights from files and directories because the topic of Linux permissions is rather broad. ### `chown` The `chown` command is used to change the owner of a file or directory. It takes a username and a file or directory as arguments. The output of the `chown` command is the file or directory that was changed. ```shell # Change the owner of a file or directory with the username "user" and file or directory "/home/user/file" chown user /home/user/file ``` #### `chown` Flags
- `-R` - Change the owner of a file or directory with the specified recursive. - `-c` - Change the owner of a file or directory with the specified verbose. - `-f` - Change the owner of a file or directory with the specified force. - `-h` - Change the owner of a file or directory with the specified symbolic links. - `-v` - Change the owner of a file or directory with the specified verbose. ```shell # Change the owner of a file or directory with the username "user" and file or directory "/home/user/file" and recursive chown -R user /home/user/file # Change the owner of a file or directory with the username "user" and file or directory "/home/user/file" and verbose chown -c user /home/user/file # Change the owner of a file or directory with the username "user" and file or directory "/home/user/file" and force chown -f user /home/user/file # Change the owner of a file or directory with the username "user" and file or directory "/home/user/file" and symbolic links chown -h user /home/user/file # Change the owner of a file or directory with the username "user" and file or directory "/home/user/file" and verbose chown -v user /home/user/file ```
### `chgrp` The `chgrp` command is used to change the group of a file or directory. It takes a group name and a file or directory as arguments. The output of the `chgrp` command is the file or directory that was changed. ```shell # Change the group of a file or directory with the group name "group" and file or directory "/home/user/file" chgrp group /home/user/file ``` #### `chgrp` Flags
- `-R` - Change the group of a file or directory with the specified recursive. - `-c` - Change the group of a file or directory with the specified verbose. - `-f` - Change the group of a file or directory with the specified force. - `-h` - Change the group of a file or directory with the specified symbolic links. - `-v` - Change the group of a file or directory with the specified verbose. ```shell # Change the group of a file or directory with the group name "group" and file or directory "/home/user/file" and recursive chgrp -R group /home/user/file # Change the group of a file or directory with the group name "group" and file or directory "/home/user/file" and verbose chgrp -c group /home/user/file # Change the group of a file or directory with the group name "group" and file or directory "/home/user/file" and force chgrp -f group /home/user/file # Change the group of a file or directory with the group name "group" and file or directory "/home/user/file" and symbolic links chgrp -h group /home/user/file # Change the group of a file or directory with the group name "group" and file or directory "/home/user/file" and verbose chgrp -v group /home/user/file ```
### `chmod` The `chmod` command is used to change the permissions of a file or directory. It takes a permission and a file or directory as arguments. The output of the `chmod` command is the file or directory that was changed. ```shell # Change the permissions of a file or directory with the permission "777" and file or directory "/home/user/file" chmod 777 /home/user/file ```
The `chmod` command can also be used to change the permissions of a file or directory using the symbolic notation. 777 is the same as `rwxrwxrwx`. The first character is for the owner, the second character is for the group, and the third character is for everyone else. 7 is the same as `rwx`. 6 is the same as `rw-`. 5 is the same as `r-x`. 4 is the same as `r--`. 3 is the same as `-wx`. 2 is the same as `-w-`. 1 is the same as `--x`. 0 is the same as `---`. #### `chmod` Flags
- `-R` - Change the permissions of a file or directory with the specified recursive. - `-c` - Change the permissions of a file or directory with the specified verbose. - `-f` - Change the permissions of a file or directory with the specified force. - `-h` - Change the permissions of a file or directory with the specified symbolic links. - `-v` - Change the permissions of a file or directory with the specified verbose. ```shell # Change the permissions of a file or directory with the permission "777" and file or directory "/home/user/file" and recursive chmod -R 777 /home/user/file # Change the permissions of a file or directory with the permission "777" and file or directory "/home/user/file" and verbose chmod -c 777 /home/user/file # Change the permissions of a file or directory with the permission "777" and file or directory "/home/user/file" and force chmod -f 777 /home/user/file # Change the permissions of a file or directory with the permission "777" and file or directory "/home/user/file" and symbolic links chmod -h 777 /home/user/file # Change the permissions of a file or directory with the permission "777" and file or directory "/home/user/file" and verbose chmod -v 777 /home/user/file ```
### `newgrp` The `newgrp` command is used to change the group of the current user. It takes a group name as an argument. The output of the `newgrp` command is the group that was changed. ```shell # Change the group of the current user with the group name "group" newgrp group ``` #### `newgrp` Flags
- `-` - Change the group of the current user with the specified login shell. - `-l` - Change the group of the current user with the specified login shell. - `-s` - Change the group of the current user with the specified login shell. ```shell # Change the group of the current user with the group name "group" and login shell newgrp - group # Change the group of the current user with the group name "group" and login shell newgrp -l group # Change the group of the current user with the group name "group" and login shell newgrp -s group ```
### `setfacl` The `setfacl` command is used to set the access control list of a file or directory. It takes a file or directory as an argument. The output of the `setfacl` command is the file or directory that was changed. ```shell # Set the access control list of a file or directory with the file or directory "/home/user/file" setfacl /home/user/file ``` #### `setfacl` Flags
- `-m` - Set the access control list of a file or directory with the specified modify. - `-x` - Set the access control list of a file or directory with the specified remove. - `-b` - Set the access control list of a file or directory with the specified remove all. - `-k` - Set the access control list of a file or directory with the specified remove default. - `-R` - Set the access control list of a file or directory with the specified recursive. - `-c` - Set the access control list of a file or directory with the specified verbose. - `-f` - Set the access control list of a file or directory with the specified force. - `-h` - Set the access control list of a file or directory with the specified symbolic links. - `-v` - Set the access control list of a file or directory with the specified verbose. ```shell # Set the access control list of a file or directory with the file or directory "/home/user/file" and modify setfacl -m /home/user/file # Set the access control list of a file or directory with the file or directory "/home/user/file" and remove setfacl -x /home/user/file # Set the access control list of a file or directory with the file or directory "/home/user/file" and remove all setfacl -b /home/user/file # Set the access control list of a file or directory with the file or directory "/home/user/file" and remove default setfacl -k /home/user/file # Set the access control list of a file or directory with the file or directory "/home/user/file" and recursive setfacl -R /home/user/file # Set the access control list of a file or directory with the file or directory "/home/user/file" and verbose setfacl -c /home/user/file # Set the access control list of a file or directory with the file or directory "/home/user/file" and force setfacl -f /home/user/file # Set the access control list of a file or directory with the file or directory "/home/user/file" and symbolic links setfacl -h /home/user/file # Set the access control list of a file or directory with the file or directory "/home/user/file" and verbose setfacl -v /home/user/file ```
### `umask` The `umask` command is used to set the default permissions of a file or directory. It takes a permission as an argument. The output of the `umask` command is the permission that was changed. ```shell # Set the default permissions of a file or directory with the permission "777" umask 777 ``` #### `umask` Flags
- `-S` - Set the default permissions of a file or directory with the specified symbolic notation. ```shell # Set the default permissions of a file or directory with the permission "777" and symbolic notation umask -S 777 ```
### `getfacl` The `getfacl` command is used to get the access control list of a file or directory. It takes a file or directory as an argument. The output of the `getfacl` command is the access control list of the file or directory. ```shell # Get the access control list of a file or directory with the file or directory "/home/user/file" getfacl /home/user/file ``` #### `getfacl` Flags
- `-R` - Get the access control list of a file or directory with the specified recursive. - `-c` - Get the access control list of a file or directory with the specified verbose. - `-f` - Get the access control list of a file or directory with the specified force. - `-h` - Get the access control list of a file or directory with the specified symbolic links. - `-v` - Get the access control list of a file or directory with the specified verbose. ```shell # Get the access control list of a file or directory with the file or directory "/home/user/file" and recursive getfacl -R /home/user/file # Get the access control list of a file or directory with the file or directory "/home/user/file" and verbose getfacl -c /home/user/file # Get the access control list of a file or directory with the file or directory "/home/user/file" and force getfacl -f /home/user/file # Get the access control list of a file or directory with the file or directory "/home/user/file" and symbolic links getfacl -h /home/user/file # Get the access control list of a file or directory with the file or directory "/home/user/file" and verbose getfacl -v /home/user/file ```
### `chattr` The `chattr` command is used to change the attributes of a file or directory. It takes a file or directory as an argument. The output of the `chattr` command is the file or directory that was changed. ```shell # Change the attributes of a file or directory with the file or directory "/home/user/file" chattr /home/user/file ``` #### `chattr` Flags
- `-i` - Change the attributes of a file or directory with the specified immutable. - `-a` - Change the attributes of a file or directory with the specified append only. - `-A` - Change the attributes of a file or directory with the specified no append. - `-d` - Change the attributes of a file or directory with the specified no dump. - `-D` - Change the attributes of a file or directory with the specified dump. - `-e` - Change the attributes of a file or directory with the specified extent. - `-E` - Change the attributes of a file or directory with the specified no extent. - `-h` - Change the attributes of a file or directory with the specified no follow. - `-H` - Change the attributes of a file or directory with the specified follow. - `-j` - Change the attributes of a file or directory with the specified data journaling. - `-J` - Change the attributes of a file or directory with the specified no data journaling. - `-s` - Change the attributes of a file or directory with the specified secure deletion. - `-S` - Change the attributes of a file or directory with the specified no secure deletion. - `-t` - Change the attributes of a file or directory with the specified notail. - `-T` - Change the attributes of a file or directory with the specified tail. - `-u` - Change the attributes of a file or directory with the specified undelete. - `-U` - Change the attributes of a file or directory with the specified no undelete. - `-v` - Change the attributes of a file or directory with the specified verbose. ```shell # Change the attributes of a file or directory with the file or directory "/home/user/file" and immutable chattr -i /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and append only chattr -a /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and no append chattr -A /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and no dump chattr -d /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and dump chattr -D /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and extent chattr -e /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and no extent chattr -E /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and no follow chattr -h /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and follow chattr -H /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and data journaling chattr -j /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and no data journaling chattr -J /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and secure deletion chattr -s /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and no secure deletion chattr -S /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and notail chattr -t /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and tail chattr -T /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and undelete chattr -u /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and no undelete chattr -U /home/user/file # Change the attributes of a file or directory with the file or directory "/home/user/file" and verbose chattr -v /home/user/file ```
### `lsattr` The `lsattr` command is used to list the attributes of a file or directory. It takes a file or directory as an argument. The output of the `lsattr` command is the attributes of the file or directory. ```shell # List the attributes of a file or directory with the file or directory "/home/user/file" lsattr /home/user/file ``` #### `lsattr` Flags
- `-R` - List the attributes of a file or directory with the specified recursive. - `-a` - List the attributes of a file or directory with the specified all. - `-d` - List the attributes of a file or directory with the specified directory. - `-h` - List the attributes of a file or directory with the specified symbolic links. - `-l` - List the attributes of a file or directory with the specified long format. - `-v` - List the attributes of a file or directory with the specified verbose. ```shell # List the attributes of a file or directory with the file or directory "/home/user/file" and recursive lsattr -R /home/user/file # List the attributes of a file or directory with the file or directory "/home/user/file" and all lsattr -a /home/user/file # List the attributes of a file or directory with the file or directory "/home/user/file" and directory lsattr -d /home/user/file # List the attributes of a file or directory with the file or directory "/home/user/file" and symbolic links lsattr -h /home/user/file # List the attributes of a file or directory with the file or directory "/home/user/file" and long format lsattr -l /home/user/file # List the attributes of a file or directory with the file or directory "/home/user/file" and verbose lsattr -v /home/user/file ```
## Check System Information You must be acquainted with these commands if you want to be a system and Linux administrator. These, such as load, CPU model, hardware model, hardware type, etc., will assist you in identifying the sort of server you are using. ### `uptime` The `uptime` command is used to display the system uptime. It takes no arguments. The output of the `uptime` command is the system uptime. ```shell # Display the system uptime uptime ``` #### `uptime` Flags
- `-p` - Display the system uptime with the specified pretty format. - `-s` - Display the system uptime with the specified since. - `-V` - Display the system uptime with the specified version. ```shell # Display the system uptime with the specified pretty format uptime -p # Display the system uptime with the specified since uptime -s # Display the system uptime with the specified version uptime -V ```
### `uname` The `uname` command is used to display the system information. It takes no arguments. The output of the `uname` command is the system information. ```shell # Display the system information uname ``` #### `uname` Flags
- `-a` - Display the system information with the specified all. - `-m` - Display the system information with the specified machine. - `-n` - Display the system information with the specified nodename. - `-r` - Display the system information with the specified kernel release. - `-s` - Display the system information with the specified kernel name. - `-v` - Display the system information with the specified kernel version. ```shell # Display the system information with the specified all uname -a # Display the system information with the specified machine uname -m # Display the system information with the specified nodename uname -n # Display the system information with the specified kernel release uname -r # Display the system information with the specified kernel name uname -s # Display the system information with the specified kernel version uname -v ```
### `lscpu` The `lscpu` command is used to display the CPU information. It takes no arguments. The output of the `lscpu` command is the CPU information. ```shell # Display the CPU information lscpu ``` #### `lscpu` Flags
- `-a` - Display the CPU information with the specified all. - `-e` - Display the CPU information with the specified extended. - `-h` - Display the CPU information with the specified human-readable. - `-i` - Display the CPU information with the specified size in bytes. - `-p` - Display the CPU information with the specified physical. - `-x` - Display the CPU information with the specified XML. ```shell # Display the CPU information with the specified all lscpu -a # Display the CPU information with the specified extended lscpu -e # Display the CPU information with the specified human-readable lscpu -h # Display the CPU information with the specified size in bytes lscpu -i # Display the CPU information with the specified physical lscpu -p # Display the CPU information with the specified XML lscpu -x ```
### `lspci` The `lspci` command is used to display the PCI information. It takes no arguments. The output of the `lspci` command is the PCI information. ```shell # Display the PCI information lspci ``` #### `lspci` Flags
- `-a` - Display the PCI information with the specified all. - `-b` - Display the PCI information with the specified brief. - `-d` - Display the PCI information with the specified device. - `-D` - Display the PCI information with the specified dump. - `-k` - Display the PCI information with the specified kernel. - `-n` - Display the PCI information with the specified numeric. - `-s` - Display the PCI information with the specified slot. - `-t` - Display the PCI information with the specified tree. - `-v` - Display the PCI information with the specified verbose. ```shell # Display the PCI information with the specified all lspci -a # Display the PCI information with the specified brief lspci -b # Display the PCI information with the specified device lspci -d # Display the PCI information with the specified dump lspci -D # Display the PCI information with the specified kernel lspci -k # Display the PCI information with the specified numeric lspci -n # Display the PCI information with the specified slot lspci -s # Display the PCI information with the specified tree lspci -t # Display the PCI information with the specified verbose lspci -v ```
### `lsusb` The `lsusb` command is used to display the USB information. It takes no arguments. The output of the `lsusb` command is the USB information. ```shell # Display the USB information lsusb ``` #### `lsusb` Flags
- `-a` - Display the USB information with the specified all. - `-b` - Display the USB information with the specified brief. - `-d` - Display the USB information with the specified device. - `-D` - Display the USB information with the specified dump. - `-k` - Display the USB information with the specified kernel. - `-n` - Display the USB information with the specified numeric. - `-s` - Display the USB information with the specified slot. - `-t` - Display the USB information with the specified tree. - `-v` - Display the USB information with the specified verbose. ```shell # Display the USB information with the specified all lsusb -a # Display the USB information with the specified brief lsusb -b # Display the USB information with the specified device lsusb -d # Display the USB information with the specified dump lsusb -D # Display the USB information with the specified kernel lsusb -k # Display the USB information with the specified numeric lsusb -n # Display the USB information with the specified slot lsusb -s # Display the USB information with the specified tree lsusb -t # Display the USB information with the specified verbose lsusb -v ```
### `free` The `free` command is used to display the memory information. It takes no arguments. The output of the `free` command is the memory information. ```shell # Display the memory information free ``` #### `free` Flags
- `-b` - Display the memory information with the specified bytes. - `-k` - Display the memory information with the specified kilobytes. - `-m` - Display the memory information with the specified megabytes. - `-g` - Display the memory information with the specified gigabytes. - `-h` - Display the memory information with the specified human-readable. - `-t` - Display the memory information with the specified total. - `-s` - Display the memory information with the specified seconds. - `-c` - Display the memory information with the specified continuous. - `-o` - Display the memory information with the specified omit header. - `-V` - Display the memory information with the specified version. ```shell # Display the memory information with the specified bytes free -b # Display the memory information with the specified kilobytes free -k # Display the memory information with the specified megabytes free -m # Display the memory information with the specified gigabytes free -g # Display the memory information with the specified human-readable free -h # Display the memory information with the specified total free -t # Display the memory information with the specified seconds free -s # Display the memory information with the specified continuous free -c # Display the memory information with the specified omit header free -o # Display the memory information with the specified version free -V ```
## Configure and Troubleshoot Network Network engineers fresh to the Linux environment can benefit from reading this section. I made an effort to include the most used network troubleshooting commands. Tcpdump, iperf, netperf, and several more networking tools are also available for debugging network-related problems, but because of their complexity, they are not included in this list. ### `ifconfig` The `ifconfig` command is used to configure and display the network interface information. It takes no arguments. The output of the `ifconfig` command is the network interface information. ```shell # Display the network interface information ifconfig ``` #### `ifconfig` Flags
- `-a` - Display the network interface information with the specified all. - `-s` - Display the network interface information with the specified summary. - `-v` - Display the network interface information with the specified verbose. - `-V` - Display the network interface information with the specified version. ```shell # Display the network interface information with the specified all ifconfig -a # Display the network interface information with the specified summary ifconfig -s # Display the network interface information with the specified verbose ifconfig -v # Display the network interface information with the specified version ifconfig -V ```
### `ip` The `ip` command is used to configure and display the network interface information. It takes no arguments. The output of the `ip` command is the network interface information. ```shell # Display the network interface information ip ``` #### `ip` Flags
- `-s` - Display the network interface information with the specified statistics. - `-d` - Display the network interface information with the specified details. - `-h` - Display the network interface information with the specified help. - `-v` - Display the network interface information with the specified verbose. - `-V` - Display the network interface information with the specified version. ```shell # Display the network interface information with the specified statistics ip -s # Display the network interface information with the specified details ip -d # Display the network interface information with the specified help ip -h # Display the network interface information with the specified verbose ip -v # Display the network interface information with the specified version ip -V ```
### `netstat` The `netstat` command is used to display the network information. It takes no arguments. The output of the `netstat` command is the network information. ```shell # Display the network information netstat ``` #### `netstat` Flags
- `-a` - Display the network information with the specified all. - `-c` - Display the network information with the specified continuous. - `-e` - Display the network information with the specified extended. - `-g` - Display the network information with the specified multicast. - `-i` - Display the network information with the specified interfaces. - `-l` - Display the network information with the specified listening. - `-m` - Display the network information with the specified memory. - `-n` - Display the network information with the specified numeric. - `-p` - Display the network information with the specified protocol. - `-r` - Display the network information with the specified routing. ```shell # Display the network information with the specified all netstat -a # Display the network information with the specified continuous netstat -c # Display the network information with the specified extended netstat -e # Display the network information with the specified multicast netstat -g # Display the network information with the specified interfaces netstat -i # Display the network information with the specified listening netstat -l # Display the network information with the specified memory netstat -m # Display the network information with the specified numeric netstat -n # Display the network information with the specified protocol netstat -p # Display the network information with the specified routing netstat -r ```
### `route` The `route` command is used to display the routing information. It takes no arguments. The output of the `route` command is the routing information. ```shell # Display the routing information route ``` #### `route` Flags
- `-n` - Display the routing information with the specified numeric. - `-v` - Display the routing information with the specified verbose. - `-V` - Display the routing information with the specified version. ```shell # Display the routing information with the specified numeric route -n # Display the routing information with the specified verbose route -v # Display the routing information with the specified version route -V ```
### `ethtool` The `ethtool` command is used to display the network interface information. It takes no arguments. The output of the `ethtool` command is the network interface information. ```shell # Display the network interface information ethtool ``` #### `ethtool` Flags
- `-a` - Display the network interface information with the specified all. - `-i` - Display the network interface information with the specified interface. - `-k` - Display the network interface information with the specified kernel. - `-S` - Display the network interface information with the specified statistics. - `-c` - Display the network interface information with the specified command. - `-h` - Display the network interface information with the specified help. - `-V` - Display the network interface information with the specified version. ```shell # Display the network interface information with the specified all ethtool -a # Display the network interface information with the specified interface ethtool -i # Display the network interface information with the specified kernel ethtool -k # Display the network interface information with the specified statistics ethtool -S # Display the network interface information with the specified command ethtool -c # Display the network interface information with the specified help ethtool -h # Display the network interface information with the specified version ethtool -V ```
### `tcpdump` The `tcpdump` command is used to capture and display the network packets. It takes no arguments. The output of the `tcpdump` command is the network packets. ```shell # Capture and display the network packets tcpdump ``` #### `tcpdump` Flags
- `-c` - Capture and display the network packets with the specified count. - `-i` - Capture and display the network packets with the specified interface. - `-n` - Capture and display the network packets with the specified numeric. - `-r` - Capture and display the network packets with the specified read. - `-s` - Capture and display the network packets with the specified snapshot. - `-w` - Capture and display the network packets with the specified write. - `-A` - Capture and display the network packets with the specified ASCII. - `-C` - Capture and display the network packets with the specified file. - `-D` - Capture and display the network packets with the specified devices. - `-F` - Capture and display the network packets with the specified output. - `-G` - Capture and display the network packets with the specified rotate. - `-H` - Capture and display the network packets with the specified hex. - `-L` - Capture and display the network packets with the specified follow. - `-N` - Capture and display the network packets with the specified no. - `-S` - Capture and display the network packets with the specified size. - `-T` - Capture and display the network packets with the specified timestamp. - `-Z` - Capture and display the network packets with the specified user. - `-d` - Capture and display the network packets with the specified decode. - `-V` - Capture and display the network packets with the specified version. ```shell # Capture and display the network packets with the specified count tcpdump -c # Capture and display the network packets with the specified interface tcpdump -i # Capture and display the network packets with the specified numeric tcpdump -n # Capture and display the network packets with the specified read tcpdump -r # Capture and display the network packets with the specified snapshot tcpdump -s # Capture and display the network packets with the specified write tcpdump -w # Capture and display the network packets with the specified ASCII tcpdump -A # Capture and display the network packets with the specified file tcpdump -C # Capture and display the network packets with the specified devices tcpdump -D # Capture and display the network packets with the specified output tcpdump -F # Capture and display the network packets with the specified rotate tcpdump -G # Capture and display the network packets with the specified hex tcpdump -H # Capture and display the network packets with the specified follow tcpdump -L # Capture and display the network packets with the specified no tcpdump -N # Capture and display the network packets with the specified size tcpdump -S # Capture and display the network packets with the specified timestamp tcpdump -T # Capture and display the network packets with the specified user tcpdump -Z # Capture and display the network packets with the specified decode tcpdump -d # Capture and display the network packets with the specified version tcpdump -V ```
### `ping` The `ping` command is used to send the ICMP echo request packets to the specified host. It takes no arguments. The output of the `ping` command is the ICMP echo reply packets. ```shell # Send the ICMP echo request packets to the specified host ping ``` #### `ping` Flags
- `-c` - Send the ICMP echo request packets to the specified host with the specified count. - `-i` - Send the ICMP echo request packets to the specified host with the specified interval. - `-I` - Send the ICMP echo request packets to the specified host with the specified interface. - `-s` - Send the ICMP echo request packets to the specified host with the specified size. - `-t` - Send the ICMP echo request packets to the specified host with the specified ttl. - `-v` - Send the ICMP echo request packets to the specified host with the specified verbose. - `-V` - Send the ICMP echo request packets to the specified host with the specified version. ```shell # Send the ICMP echo request packets to the specified host with the specified count ping -c # Send the ICMP echo request packets to the specified host with the specified interval ping -i # Send the ICMP echo request packets to the specified host with the specified interface ping -I # Send the ICMP echo request packets to the specified host with the specified size ping -s # Send the ICMP echo request packets to the specified host with the specified ttl ping -t # Send the ICMP echo request packets to the specified host with the specified verbose ping -v # Send the ICMP echo request packets to the specified host with the specified version ping -V ```
### `traceroute` The `traceroute` command is used to trace the route to the specified host. It takes no arguments. The output of the `traceroute` command is the route to the specified host. ```shell # Trace the route to the specified host traceroute ``` #### `traceroute` Flags
- `-d` - Trace the route to the specified host with the specified debug. - `-f` - Trace the route to the specified host with the specified first. - `-g` - Trace the route to the specified host with the specified gateway. - `-I` - Trace the route to the specified host with the specified interface. - `-m` - Trace the route to the specified host with the specified max. - `-n` - Trace the route to the specified host with the specified numeric. - `-p` - Trace the route to the specified host with the specified port. - `-q` - Trace the route to the specified host with the specified query. - `-s` - Trace the route to the specified host with the specified source. - `-t` - Trace the route to the specified host with the specified ttl. - `-v` - Trace the route to the specified host with the specified verbose. - `-V` - Trace the route to the specified host with the specified version. ```shell # Trace the route to the specified host with the specified debug traceroute -d # Trace the route to the specified host with the specified first traceroute -f # Trace the route to the specified host with the specified gateway traceroute -g # Trace the route to the specified host with the specified interface traceroute -I # Trace the route to the specified host with the specified max traceroute -m # Trace the route to the specified host with the specified numeric traceroute -n # Trace the route to the specified host with the specified port traceroute -p # Trace the route to the specified host with the specified query traceroute -q # Trace the route to the specified host with the specified source traceroute -s # Trace the route to the specified host with the specified ttl traceroute -t # Trace the route to the specified host with the specified verbose traceroute -v # Trace the route to the specified host with the specified version traceroute -V ```
### `dig` The `dig` command is used to query the DNS name servers. It takes no arguments. The output of the `dig` command is the DNS name servers. ```shell # Query the DNS name servers dig ``` #### `dig` Flags
- `-a` - Query the DNS name servers with the specified all. - `-b` - Query the DNS name servers with the specified bind. - `-c` - Query the DNS name servers with the specified class. - `-d` - Query the DNS name servers with the specified debug. - `-f` - Query the DNS name servers with the specified file. - `-i` - Query the DNS name servers with the specified interface. - `-k` - Query the DNS name servers with the specified key. - `-m` - Query the DNS name servers with the specified max. - `-n` - Query the DNS name servers with the specified numeric. - `-p` - Query the DNS name servers with the specified port. - `-q` - Query the DNS name servers with the specified query. - `-r` - Query the DNS name servers with the specified recurse. - `-s` - Query the DNS name servers with the specified server. - `-t` - Query the DNS name servers with the specified type. - `-v` - Query the DNS name servers with the specified verbose. - `-V` - Query the DNS name servers with the specified version. ```shell # Query the DNS name servers with the specified all dig -a # Query the DNS name servers with the specified bind dig -b # Query the DNS name servers with the specified class dig -c # Query the DNS name servers with the specified debug dig -d # Query the DNS name servers with the specified file dig -f # Query the DNS name servers with the specified interface dig -i # Query the DNS name servers with the specified key dig -k # Query the DNS name servers with the specified max dig -m # Query the DNS name servers with the specified numeric dig -n # Query the DNS name servers with the specified port dig -p # Query the DNS name servers with the specified query dig -q # Query the DNS name servers with the specified recurse dig -r # Query the DNS name servers with the specified server dig -s # Query the DNS name servers with the specified type dig -t # Query the DNS name servers with the specified verbose dig -v # Query the DNS name servers with the specified version dig -V ```
### `nslookup` The `nslookup` command is used to query the DNS name servers. It takes no arguments. The output of the `nslookup` command is the DNS name servers. ```shell # Query the DNS name servers nslookup ``` #### `nslookup` Flags
- `-a` - Query the DNS name servers with the specified all. - `-b` - Query the DNS name servers with the specified bind. - `-c` - Query the DNS name servers with the specified class. - `-d` - Query the DNS name servers with the specified debug. - `-f` - Query the DNS name servers with the specified file. - `-i` - Query the DNS name servers with the specified interface. - `-k` - Query the DNS name servers with the specified key. - `-m` - Query the DNS name servers with the specified max. - `-n` - Query the DNS name servers with the specified numeric. - `-p` - Query the DNS name servers with the specified port. - `-q` - Query the DNS name servers with the specified query. - `-r` - Query the DNS name servers with the specified recurse. - `-s` - Query the DNS name servers with the specified server. - `-t` - Query the DNS name servers with the specified type. - `-v` - Query the DNS name servers with the specified verbose. - `-V` - Query the DNS name servers with the specified version. ```shell # Query the DNS name servers with the specified all nslookup -a # Query the DNS name servers with the specified bind nslookup -b # Query the DNS name servers with the specified class nslookup -c # Query the DNS name servers with the specified debug nslookup -d # Query the DNS name servers with the specified file nslookup -f # Query the DNS name servers with the specified interface nslookup -i # Query the DNS name servers with the specified key nslookup -k # Query the DNS name servers with the specified max nslookup -m # Query the DNS name servers with the specified numeric nslookup -n # Query the DNS name servers with the specified port nslookup -p # Query the DNS name servers with the specified query nslookup -q # Query the DNS name servers with the specified recurse nslookup -r # Query the DNS name servers with the specified server nslookup -s # Query the DNS name servers with the specified type nslookup -t # Query the DNS name servers with the specified verbose nslookup -v # Query the DNS name servers with the specified version nslookup -V ```
### `host` The `host` command is used to query the DNS name servers. It takes no arguments. The output of the `host` command is the DNS name servers. ```shell # Query the DNS name servers host ``` #### `host` Flags
- `-a` - Query the DNS name servers with the specified all. - `-b` - Query the DNS name servers with the specified bind. - `-c` - Query the DNS name servers with the specified class. - `-d` - Query the DNS name servers with the specified debug. - `-f` - Query the DNS name servers with the specified file. - `-i` - Query the DNS name servers with the specified interface. - `-k` - Query the DNS name servers with the specified key. - `-m` - Query the DNS name servers with the specified max. - `-n` - Query the DNS name servers with the specified numeric. - `-p` - Query the DNS name servers with the specified port. - `-q` - Query the DNS name servers with the specified query. - `-r` - Query the DNS name servers with the specified recurse. - `-s` - Query the DNS name servers with the specified server. - `-t` - Query the DNS name servers with the specified type. - `-v` - Query the DNS name servers with the specified verbose. - `-V` - Query the DNS name servers with the specified version. ```shell # Query the DNS name servers with the specified all host -a # Query the DNS name servers with the specified bind host -b # Query the DNS name servers with the specified class host -c # Query the DNS name servers with the specified debug host -d # Query the DNS name servers with the specified file host -f # Query the DNS name servers with the specified interface host -i # Query the DNS name servers with the specified key host -k # Query the DNS name servers with the specified max host -m # Query the DNS name servers with the specified numeric host -n # Query the DNS name servers with the specified port host -p # Query the DNS name servers with the specified query host -q # Query the DNS name servers with the specified recurse host -r # Query the DNS name servers with the specified server host -s # Query the DNS name servers with the specified type host -t # Query the DNS name servers with the specified verbose host -v # Query the DNS name servers with the specified version host -V ```
### `drill` The `drill` command is used to query the DNS name servers. It takes no arguments. The output of the `drill` command is the DNS name servers. ```shell # Query the DNS name servers drill ``` #### `drill` Flags
- `-a` - Query the DNS name servers with the specified all. - `-b` - Query the DNS name servers with the specified bind. - `-c` - Query the DNS name servers with the specified class. - `-d` - Query the DNS name servers with the specified debug. - `-f` - Query the DNS name servers with the specified file. - `-i` - Query the DNS name servers with the specified interface. - `-k` - Query the DNS name servers with the specified key. - `-m` - Query the DNS name servers with the specified max. - `-n` - Query the DNS name servers with the specified numeric. - `-p` - Query the DNS name servers with the specified port. - `-q` - Query the DNS name servers with the specified query. - `-r` - Query the DNS name servers with the specified recurse. - `-s` - Query the DNS name servers with the specified server. - `-t` - Query the DNS name servers with the specified type. - `-v` - Query the DNS name servers with the specified verbose. - `-V` - Query the DNS name servers with the specified version. ```shell # Query the DNS name servers with the specified all drill -a # Query the DNS name servers with the specified bind drill -b # Query the DNS name servers with the specified class drill -c # Query the DNS name servers with the specified debug drill -d # Query the DNS name servers with the specified file drill -f # Query the DNS name servers with the specified interface drill -i # Query the DNS name servers with the specified key drill -k # Query the DNS name servers with the specified max drill -m # Query the DNS name servers with the specified numeric drill -n # Query the DNS name servers with the specified port drill -p # Query the DNS name servers with the specified query drill -q # Query the DNS name servers with the specified recurse drill -r # Query the DNS name servers with the specified server drill -s # Query the DNS name servers with the specified type drill -t # Query the DNS name servers with the specified verbose drill -v # Query the DNS name servers with the specified version drill -V ```
### `ss` The `ss` command is used to query the DNS name servers. It takes no arguments. The output of the `ss` command is the DNS name servers. ```shell # Query the DNS name servers ss ``` #### `ss` Flags
- `-a` - Query the DNS name servers with the specified all. - `-b` - Query the DNS name servers with the specified bind. - `-c` - Query the DNS name servers with the specified class. - `-d` - Query the DNS name servers with the specified debug. - `-f` - Query the DNS name servers with the specified file. - `-i` - Query the DNS name servers with the specified interface. - `-k` - Query the DNS name servers with the specified key. - `-m` - Query the DNS name servers with the specified max. - `-n` - Query the DNS name servers with the specified numeric. - `-p` - Query the DNS name servers with the specified port. - `-q` - Query the DNS name servers with the specified query. - `-r` - Query the DNS name servers with the specified recurse. - `-s` - Query the DNS name servers with the specified server. - `-t` - Query the DNS name servers with the specified type. - `-v` - Query the DNS name servers with the specified verbose. - `-V` - Query the DNS name servers with the specified version. ```shell # Query the DNS name servers with the specified all ss -a # Query the DNS name servers with the specified bind ss -b # Query the DNS name servers with the specified class ss -c # Query the DNS name servers with the specified debug ss -d # Query the DNS name servers with the specified file ss -f # Query the DNS name servers with the specified interface ss -i # Query the DNS name servers with the specified key ss -k # Query the DNS name servers with the specified max ss -m # Query the DNS name servers with the specified numeric ss -n # Query the DNS name servers with the specified port ss -p # Query the DNS name servers with the specified query ss -q # Query the DNS name servers with the specified recurse ss -r # Query the DNS name servers with the specified server ss -s # Query the DNS name servers with the specified type ss -t # Query the DNS name servers with the specified verbose ss -v # Query the DNS name servers with the specified version ss -V ```
### `wget` The `wget` command is used to query the DNS name servers. It takes no arguments. The output of the `wget` command is the DNS name servers. ```shell # Query the DNS name servers wget ``` #### `wget` Flags
- `-a` - Query the DNS name servers with the specified all. - `-b` - Query the DNS name servers with the specified bind. - `-c` - Query the DNS name servers with the specified class. - `-d` - Query the DNS name servers with the specified debug. - `-f` - Query the DNS name servers with the specified file. - `-i` - Query the DNS name servers with the specified interface. - `-k` - Query the DNS name servers with the specified key. - `-m` - Query the DNS name servers with the specified max. - `-n` - Query the DNS name servers with the specified numeric. - `-p` - Query the DNS name servers with the specified port. - `-q` - Query the DNS name servers with the specified query. - `-r` - Query the DNS name servers with the specified recurse. - `-s` - Query the DNS name servers with the specified server. - `-t` - Query the DNS name servers with the specified type. - `-v` - Query the DNS name servers with the specified verbose. - `-V` - Query the DNS name servers with the specified version. ```shell # Query the DNS name servers with the specified all wget -a # Query the DNS name servers with the specified bind wget -b # Query the DNS name servers with the specified class wget -c # Query the DNS name servers with the specified debug wget -d # Query the DNS name servers with the specified file wget -f # Query the DNS name servers with the specified interface wget -i # Query the DNS name servers with the specified key wget -k # Query the DNS name servers with the specified max wget -m # Query the DNS name servers with the specified numeric wget -n # Query the DNS name servers with the specified port wget -p # Query the DNS name servers with the specified query wget -q # Query the DNS name servers with the specified recurse wget -r # Query the DNS name servers with the specified server wget -s # Query the DNS name servers with the specified type wget -t # Query the DNS name servers with the specified verbose wget -v # Query the DNS name servers with the specified version wget -V ```
### `curl` The `curl` command is used to query the DNS name servers. It takes no arguments. The output of the `curl` command is the DNS name servers. ```shell # Query the DNS name servers curl ``` #### `curl` Flags
- `-a` - Query the DNS name servers with the specified all. - `-b` - Query the DNS name servers with the specified bind. - `-c` - Query the DNS name servers with the specified class. - `-d` - Query the DNS name servers with the specified debug. - `-f` - Query the DNS name servers with the specified file. - `-i` - Query the DNS name servers with the specified interface. - `-k` - Query the DNS name servers with the specified key. - `-m` - Query the DNS name servers with the specified max. - `-n` - Query the DNS name servers with the specified numeric. - `-p` - Query the DNS name servers with the specified port. - `-q` - Query the DNS name servers with the specified query. - `-r` - Query the DNS name servers with the specified recurse. - `-s` - Query the DNS name servers with the specified server. - `-t` - Query the DNS name servers with the specified type. - `-v` - Query the DNS name servers with the specified verbose. - `-V` - Query the DNS name servers with the specified version. ```shell # Query the DNS name servers with the specified all curl -a # Query the DNS name servers with the specified bind curl -b # Query the DNS name servers with the specified class curl -c # Query the DNS name servers with the specified debug curl -d # Query the DNS name servers with the specified file curl -f # Query the DNS name servers with the specified interface curl -i # Query the DNS name servers with the specified key curl -k # Query the DNS name servers with the specified max curl -m # Query the DNS name servers with the specified numeric curl -n # Query the DNS name servers with the specified port curl -p # Query the DNS name servers with the specified query curl -q # Query the DNS name servers with the specified recurse curl -r # Query the DNS name servers with the specified server curl -s # Query the DNS name servers with the specified type curl -t # Query the DNS name servers with the specified verbose curl -v # Query the DNS name servers with the specified version curl -V ```
### `nmap` The `nmap` command is used to query the DNS name servers. It takes no arguments. The output of the `nmap` command is the DNS name servers. ```shell # Query the DNS name servers nmap ``` #### `nmap` Flags
- `-A` - Query the DNS name servers with the specified all. - `-V` - Query the DNS name servers with the specified version. ```shell # Query the DNS name servers with the specified all nmap -A # Query the DNS name servers with the specified version nmap -V ```
## Manage System Processes You may control Linux processes and troubleshoot any server resource-related issues with the use of these Linux commands. These commands let you keep an eye on your server's RAM, CPU, disk IO, and other resources. ### `ps` The `ps` command is used to list the processes running on the system. It takes no arguments. The output of the `ps` command is the processes running on the system. ```shell # List the processes running on the system ps ``` #### `ps` Flags
- `-a` - List the processes running on the system with the specified all. - `-f` - List the processes running on the system with the specified full. - `-l` - List the processes running on the system with the specified long. - `-u` - List the processes running on the system with the specified user. ```shell # List the processes running on the system with the specified all ps -a # List the processes running on the system with the specified full ps -f # List the processes running on the system with the specified long ps -l # List the processes running on the system with the specified user ps -u ```
### `top` The `top` command is used to display the processes running on the system. It takes no arguments. The output of the `top` command is the processes running on the system. ```shell # Display the processes running on the system top ``` #### `top` Flags
- `-b` - Display the processes running on the system with the specified batch. - `-c` - Display the processes running on the system with the specified command. - `-d` - Display the processes running on the system with the specified delay. - `-h` - Display the processes running on the system with the specified help. - `-i` - Display the processes running on the system with the specified idle. - `-n` - Display the processes running on the system with the specified iterations. - `-p` - Display the processes running on the system with the specified pid. - `-s` - Display the processes running on the system with the specified sort. - `-u` - Display the processes running on the system with the specified user. - `-v` - Display the processes running on the system with the specified version. ```shell # Display the processes running on the system with the specified batch top -b # Display the processes running on the system with the specified command top -c # Display the processes running on the system with the specified delay top -d # Display the processes running on the system with the specified help top -h # Display the processes running on the system with the specified idle top -i # Display the processes running on the system with the specified iterations top -n # Display the processes running on the system with the specified pid top -p # Display the processes running on the system with the specified sort top -s # Display the processes running on the system with the specified user top -u # Display the processes running on the system with the specified version top -v ```
### `kill` The `kill` command is used to kill a process. It takes one argument. The output of the `kill` command is the killed process. ```shell # Kill a process kill ``` #### `kill` Flags
- `-l` - Kill a process with the specified list. ```shell # Kill a process with the specified list kill -l ```
### `killall` The `killall` command is used to kill a process. It takes one argument. The output of the `killall` command is the killed process. ```shell # Kill a process killall ``` #### `killall` Flags
- `-l` - Kill a process with the specified list. ```shell # Kill a process with the specified list killall -l ```
### `pkill` The `pkill` command is used to kill a process. It takes one argument. The output of the `pkill` command is the killed process. ```shell # Kill a process pkill ``` #### `pkill` Flags
- `-l` - Kill a process with the specified list. ```shell # Kill a process with the specified list pkill -l ```
### `pgrep` The `pgrep` command is used to kill a process. It takes one argument. The output of the `pgrep` command is the killed process. ```shell # Kill a process pgrep ``` #### `pgrep` Flags
- `-l` - Kill a process with the specified list. ```shell # Kill a process with the specified list pgrep -l ```
### `nice` The `nice` command is used to run a process with a nice value. It takes one argument. The output of the `nice` command is the process with a nice value. ```shell # Run a process with a nice value nice ``` #### `nice` Flags
- `-n` - Run a process with a nice value with the specified nice. - `-p` - Run a process with a nice value with the specified pid. - `-v` - Run a process with a nice value with the specified verbose. ```shell # Run a process with a nice value with the specified nice nice -n # Run a process with a nice value with the specified pid nice -p # Run a process with a nice value with the specified verbose nice -v ```
### `renice` The `renice` command is used to run a process with a nice value. It takes one argument. The output of the `renice` command is the process with a nice value. ```shell # Run a process with a nice value renice ``` #### `renice` Flags
- `-n` - Run a process with a nice value with the specified nice. - `-p` - Run a process with a nice value with the specified pid. - `-v` - Run a process with a nice value with the specified verbose. ```shell # Run a process with a nice value with the specified nice renice -n # Run a process with a nice value with the specified pid renice -p # Run a process with a nice value with the specified verbose renice -v ```
### `at` The `at` command is used to run a process at a specified time. It takes one argument. The output of the `at` command is the process at a specified time. ```shell # Run a process at a specified time at