Common SSH Commands in Linux With Examples

SSH is the short form of Secure Shell or Secure Socket Shell. SSH is an encrypted protocol to connect and communicate between two systems using a secured link over an unsecured network. Tatu Ylonen developed it in 1995. The SSH protocol’s three layers are the authentication, transport, and connection layers.

SSH commands in Linux

SSH command is a command used in Linux. There are many SSH commands in Linux, such as terminal commands, file listing commands, etc. Following are the commonly used SSH commands in Linux. 

• ls Command
• cd Command
• pwd Command
• In Command
• mkdir Command
• rm Command
• cat Command
• cp Command
• mv Command
• kill Command
• chmod Command
• wc Command
• rmdir Command
• tail Command
• more Command
• grep Command
• find Command
• pico Command
• vi/nano Command
• history Command
• clear Command
• tar Command
• file Command
• wget Command
• du Command
• du -sh Command
• ps Command
• touch Command
• last Command
• netstat Command
• zip Command
• unzip Command
• reset Command
• exit Command

ls Command

ls Command is a directory and file listing command. It lists the directory content, i.e.; files and directories. 

Syntax: ls [Options] [File]

ls command can be customized with several options to differentiate the outcomes. The commonly used options in ls command are the following. 

• ls -a

ls -a display all files including hidden file starting with the dot (.).

Example:

ls -d */ displays only the sub-directories.

Example:

• ls -l

ls -l displays full information about files, such as file name, size, modified date and time, the owner, and the permissions in long listing format.

Example:

• ls -F

ls -F displays files with special characters such as *, @, etc.

Example:

• ls -sh

ls -sh displays the file sizes in human-readable format.

Example:

• ls -lh

ls -lh displays full information about file names in human-readable format.

Example:

• ls -r

ls -r display all files in reverse alphabetic order.

Example: 

• ls –version

ls –version displays the version of the ls command.

Example:

• ls -ltr

ls -ltr displays a long list of files based on modification date in reverse output order.

Example:

• ls -t

ls -t display files based on modification time & date, i.e.; displays the last edited file first.

Example:

• ls -n

ls -n displays each file’s User ID and Group ID instead of their names.

Example:

• ls -m

ls -m displays a list of files separated by commas.

Example:

• ls -g

 ls -g displays full information about files, such as file name, size, modified date and time, and permissions in long listing format by excluding the owner and group information.

Example:

• ls -i

ls -i display the index number of files.

Example:

cd Command

The cd command is used to switch, jump, or move into another directory without typing the entire file path. cd means change directory.

Syntax: cd [Options] [Directory]

cd command can be customized with many options to differentiate the outcomes. The commonly used options in cd command are the following. 

• cd /

cd / is used to switch to the root or parent directory from any other directory.

Example:

shibi@linux:~$ cd /

shibi@linux:/$ pwd

/

shibi@linux:/$

• cd ~

cd ~ is used to switch back to the home directory from any other directory.

Example:

shibi@linux:~/documens/father/stepfather$ cd ~

shibi@linux:~$ pwd

 /home/shibi

abhi@linux:~$

• cd ..

cd .. is used to switch to the previous directory.

Example:

shibi@linux:~/parent/baby directory$ pwd

/home/abhi/parent/baby directory

shibi@linux:~/parent/baby directory$ cd ..

shibi@linux:~/parent$ pwd

/home/shibi/parent

shibi@linux:~/parent$

• cd ../..

cd ../.. is used to switch back multiple directories.

Example:

shibi@linux:~/parent/baby directory$ cd ../..

shibi@linux:~/parent$ pwd

/home/shibi/parent

shibi@linux:~/parent$

• cd –

cd – is used to return to previous directory.

Example:

• cd dir_name

cd dir_name is used to obtain the relative pathname.

Example:

shibi@linux:~/parent$ ls

son1 ‘son directory’

shibi@linux:~/parent$ cd son1

shibi@linux:~/parent/son1$

pwd command

The pwd command is used to get the full path name from the root directory to the current directory. pwd means print working directory. The exit statuses of pwd command are zero (success) and non-zero (failure).

Syntax: pwd [option]

pwd command can be customized with many options to differentiate the outcomes. The commonly used options in pwd command are the following. 

• pwd -L

pwd -L displays symbolic links instead of absolute paths.

Example:

• pwd -P

pwd -P displays the absolute path of the working directory and avoids symbolic links.

Example:

• pwd – – version

pwd – – version is used to check the version of the system.

Example:

Written by Jim Meyering.

shibi@linux:~$

• pwd – -help

pwd – -help displays the pwd command help file with a list of available options.

Example:

shibi@linux-vm:~$ pwd – -help 

pwd: pwd [-LP] 

Print the name of the current working directory. 

Options : 

-L  print the value of $ PWD if it names the current working directory 

-P  print the physical directory, without any symbolic links 

By default, ` pwd ‘behaves as if` -L ‘ were specified.

Exit Status: Returns 0 unless an invalid option is given or the current directory cannot be read.

In Command

ln command is used to create soft links and hard links between files in Linux. ln means link. It has three forms. 1st form specifies the source file and destination to be linked. 2nd form specify the source file and directory to be linked. 3rd form specifies the directory name and a file to be linked to the directory.

ln command can be customized with many options to differentiate the outcomes. The commonly used options in ln command are the following. 

• ln -v (version)

ln -v displays version details.

Example:

shibi@linux:~$

• ln -v (verbose)

ln -v  displays the name of each file linked.

Example:

‘test_dir1/exfile2.txt’ = > ‘exfile2.txt’

‘test_dir1/exfile3.txt’ = > ‘exfile3.txt’

shibi@linux:~/fastexample$

• ln -h (help)

ln -h displays the ln command help file with a list of details.

Example:

shibi@linux:~/fastexample$ ls 

exfile1.txt   exfile2.txt   exfile3.txt   test_dir   test_dir1

shibi@linux:~/fastexample$ clear 

shibi@linux:~/fastexample$ In – -help 

Usage: In [OPTION]… [-T] TARGET LINK_NAME.    (1st form) 

       or: In [OPTION]… TARGET                                   (2nd form)  

       or: In [OPTION]… TARGET… DIRECTORY          (3rd form)  

       or: In [OPTION]… -t DIRECTORY TARGET…       (4th form) 

]In the 1st form, create a link to TARGET with the name LINK_NAME.

In the 2nd form, create a link to TARGET in the current directory.

In the 3rd and 4th forms, create links to each TARGET in DIRECTORY.

Create hard links by default, symbolic links with – -symbolic.

By default, each destination (name of new link) should not already exist. 

When creating hard links, each TARGET must exist.  

Symbolic links can hold arbitrary text; if later resolved, a relative link is interpreted in relation to its parent directory.

Mandatory arguments to long options are mandatory for short options too.

   – -backup[= CONTROL]    make a backup of each existing destination file 

-b                                           like – backup but does not accept an argument 

-d, -f, -directory                allow the superuser to attempt to hard link 

                                          directories (note: will probably fail due to 

                                          system restrictions, even for the superuser) 

-f, – – force                        remove existing destination files 

-i , –interactive                prompt whether to remove destinations 

-L , –logical                     dereference TARGETS that are symbolic links

-n, – -no-dereference       treat LINK_NAME as a normal file if 

                                         it is a symbolic link to a directory 

-P, – -physical                  make hard links directly to symbolic links

-r, – -relative                    create symbolic links relative to link location 

-s, – -symbolic                make symbolic links instead of hard links 

-S , – -suffix = SUFFIX     override the usual backup suffix

-t, – -target-directory=DIRECTORY  specify the DIRECTORY in which to create

                                                    the links

mkdir Command

mkdir command is used to create a new file or directory. mkdir means make directory. You only need to specify the new folder’s name and verify that it does not already exist. This command is capable of simultaneously creating multiple directories and setting their permissions.

Syntax: mkdir [options] [directory name]

mkdir command can be customized with many options to differentiate the outcomes. The commonly used options in the ln command are the following. 

• mkdir – -version

mkdir – -version displays version details.

Example:

Written by David Makinze.

shibi@linux:~/GFG $

• mkdir -v

mkdir -v displays a message every time a new directory is created.

Example:

shibi@linux:~/GFG $  mkdir -v one two three 

mkdir: created directory ‘one’ 

mkdir: created directory ‘two’ 

mkdir: created directory ‘three’ 

shibi@linux:~/GFG $  ls 

one three two 

shibi@linux:~/GFG $ 

• mkdir -p

mkdir -p is used to create subdirectories without reporting any error.

Example:

shibi@linux:~/GFG $  mkdir -p -v first/second/third

mkdir: created directory ‘first’ 

mkdir: created directory ‘first/second’ 

mkdir: created directory ‘first/second/third’ 

shibi@linux:~/GFG $  ls 

• mkdir – -help

mkdir – -help displays the mkdir command help file with a list of details.

Example:

shibi@linux: ~/GFG $  mkdir – -help 

Usage: mkdir [OPTION]… DIRECTORY… 

Create the DIRECTORY (ies), if they do not already exist . 

Mandatory arguments to long options are mandatory for short options too.

-m , – -mode = MODE    set file mode (as in chmod), not a=rwx – umask

-p , – -parents                  no error if existing, make parent directories as needed

-V , – -verbose                 print a message for each created directory 

-Z                                     set SELinux security context of each created directory

                                         to the default type 

       — context [=CTX]     like -Z , or if CTX is specified then set the SELinux

                                         or SMACK security context to CTX 

      – -help                        display this help and exit 

      – -version                  output version information and exit 

GNU coreutils online help: <http://www.gnu.org/software/coreutils/> 

Full documentation at: <http://www.gnu.org/software/coreutils/mkdir> 

or available locally via: info ‘(coreutils) mkdir invocation’ 

shibi@linux: ~/GFG $ 

• mkdir -m a=rwx

mkdir -m a=rwx is used to set the permission to read, write, and execute on the created directory.

Example:

shibi@linux: ~/GFG $  mkdir -m a=rwx

shibi@linux: ~/GFG $  ls

1png              College

5555              farewell   2022-04-12   12:45:7png

linux.docx.    farewell   2022-04-11    12:42:7.png

linuxfun.pdf

shibi@linux: ~/GFG $

rm Command

The rm command removes objects from the file system, such as directories, files, symbolic links, etc. rm means to remove.

Syntax: rm [options] [file_name]

rm command can be customized with many options to differentiate the outcomes. The commonly used options in the rm command are the following. 

• rm -r

rm -r is used for recursive deletion. It removes all files and subfolders in the directory without asking for confirmation.

Example: rm -r home/document/games

• rm -f

rm -f is used for force deletion. It removes the file forcefully by overriding minor protection. It will not remove write-protect directories. 

Example: rm -f super.txt

• rm -i

rm -i is used for Interactive deletion. It asks for confirmation from the user before removing each file.

Example: rm -i super.txt

cat Command

The cat command displays the file’s contents after reading the data. Cat means concatenate. It is used to create, view, and combine files.

Syntax: cat [options] [file_name]

cat command can be customized with many options to differentiate the outcomes. The commonly used options in the cat command are the following. 

• cat -n

cat-n displays the contents of a file preceding with line numbers.

Example: cat-n will show the content of a file with a line number.

• cat >

cat > is used to create a file.

Example: cat > shibi will create a file named shibi.

• cat -v

cat -v displays non-printable characters.

Example: cat -v will display non-printable characters.

• cat -s

cat -n suppress the repeated empty line in the content.

Example: cat -n will eliminate the repeated empty line.

• cat -E

cat -E displays characters at the end of the line highlighted.

Example: cat -E will highlight the end of the line.

cp Command

cp Command is used to copy folders, files, and directories from one location to another. cp means to copy.

Syntax: cp [options] [source] [destination]

cp command can be customized with many options to differentiate the outcomes. The commonly used options in the cp command are -i (interactive), -f (force), -p (preserve), -b (backup), -a (archive), and -n (no overwrite)

mv Command

mv Command is used to move folders, files, and directories from one location to another. It performs two functions, such as moving files and renaming files. mv means to move. 

Syntax: mv [options] [source] [destination]

mv command can be customized with many options to differentiate the outcomes. The commonly used options in the cp command are -i (interactive), -f (force), -b (backup), and -n (no overwrite)

Conclusion

SSH is used for logging in to a shell on a remote host, file listing, creating folders, removing files, setting up automatic logging into a remote server, tunneling sensitive data, securely and efficiently backing up, copying, and mirroring files, forwarding a port, securing file transfer protocols, etc. SSH login credentials and SSH client is required to use SSH. On Linux, a native Terminal app is used for the connection.