{"id":254,"date":"2016-02-25T15:36:54","date_gmt":"2016-02-25T20:36:54","guid":{"rendered":"http:\/\/underhost.com\/blog\/?p=254"},"modified":"2026-07-20T14:34:13","modified_gmt":"2026-07-20T18:34:13","slug":"common-ssh-commands-or-linux-shell-commands","status":"publish","type":"post","link":"https:\/\/underhost.com\/blog\/common-ssh-commands-or-linux-shell-commands\/","title":{"rendered":"Common SSH Commands or Linux Shell Commands"},"content":{"rendered":"

<\/p>\n

\n
Linux Server Administration<\/div>\n

Common SSH Commands and Linux Shell Commands<\/h1>\n

A practical command-line reference for VPS, dedicated server, and Linux hosting administration<\/h2>\n

Learn how to connect securely, manage files, inspect services, troubleshoot network problems, review logs, monitor resources, maintain packages, and protect your Linux server.<\/p>\n<\/div>\n

<\/p>\n

SSH gives administrators direct and encrypted access to a Linux server.<\/strong>
\nWith the commands in this guide, you can manage a
\nCloud VPS<\/a>,
\nOffshore VPS<\/a>,
\nor
\ndedicated server<\/a>
\nwithout relying entirely on a graphical control panel.<\/div>\n

<\/p>\n

Important command-line safety notice<\/strong>
\nCommands executed as root<\/code> or through sudo<\/code> can modify the entire server. Confirm the command, path, filename, and backup status before deleting files, changing permissions recursively, modifying firewall rules, or restarting production services.<\/div>\n

<\/p>\n

\n

Command categories covered<\/h2>\n
SSH connections and keys<\/a>
\nServer and OS information<\/a>
\nDirectory navigation<\/a>
\nFiles and directories<\/a>
\nViewing and editing files<\/a>
\nSearching files and text<\/a>
\nPermissions and ownership<\/a>
\nUsers and groups<\/a>
\nPackage management<\/a>
\nServices and systemd<\/a>
\nProcesses and resources<\/a>
\nDisk and storage<\/a>
\nNetworking and DNS<\/a>
\nFirewall commands<\/a>
\nLogs and troubleshooting<\/a>
\nTransfers and backups<\/a>
\nArchives and compression<\/a>
\nCron jobs<\/a><\/div>\n<\/div>\n
\n

1. SSH connection commands<\/h2>\n

SSH, or Secure Shell, creates an encrypted connection between your computer and a remote Linux server. Most Linux VPS and dedicated server administration begins with the ssh<\/code> command.<\/p>\n

Connect using the default SSH port<\/h3>\n
ssh username@server_ip<\/code><\/pre>\n
Example:<\/p>\n
ssh root@203.0.113.10<\/code><\/pre>\n
Connect using a custom SSH port<\/h3>\n
ssh -p 2222 username@server_ip<\/code><\/pre>\n
Connect using a private key<\/h3>\n
ssh -i ~\/.ssh\/server_key username@server_ip<\/code><\/pre>\n
Create a modern SSH key pair<\/h3>\n
ssh-keygen -t ed25519 -a 100<\/code><\/pre>\n
Store the private key securely and protect it with a strong passphrase. Never send a private SSH key through email, chat, or a support ticket.<\/p>\n
Copy your public key to the server<\/h3>\n
ssh-copy-id username@server_ip<\/code><\/pre>\n
For a custom SSH port:<\/p>\n
ssh-copy-id -p 2222 username@server_ip<\/code><\/pre>\n
Test the SSH connection with detailed output<\/h3>\n
ssh -vvv username@server_ip<\/code><\/pre>\n
Verbose output helps diagnose authentication failures, key problems, connection timeouts, and SSH negotiation errors.<\/p>\n
Keep an idle SSH connection alive<\/h3>\n
ssh -o ServerAliveInterval=60 username@server_ip<\/code><\/pre>\n
Run one command remotely<\/h3>\n
ssh username@server_ip \"uptime\"<\/code><\/pre>\n
Close the SSH session<\/h3>\n
exit<\/code><\/pre>\n
SSH hardening tip:<\/strong>
\nBefore disabling password authentication or direct root access, confirm that key-based authentication works in a second terminal window. Incorrect SSH changes can lock you out of the server.<\/div>\n
2. Check server, operating system, and kernel information<\/h2>\n
Show the hostname<\/h3>\n
hostname<\/code><\/pre>\n
Show detailed hostname information<\/h3>\n
hostnamectl<\/code><\/pre>\n
Change the server hostname<\/h3>\n
sudo hostnamectl set-hostname server.example.com<\/code><\/pre>\n
Also review \/etc\/hosts<\/code> after changing a hostname so local hostname resolution remains correct.<\/p>\n
Show the Linux distribution and version<\/h3>\n
cat \/etc\/os-release<\/code><\/pre>\n
Show kernel and architecture information<\/h3>\n
uname -a<\/code><\/pre>\n
uname -r<\/code><\/pre>\n
uname -m<\/code><\/pre>\n
Show CPU information<\/h3>\n
lscpu<\/code><\/pre>\n
Show memory information<\/h3>\n
free -h<\/code><\/pre>\n
Show server uptime and load averages<\/h3>\n
uptime<\/code><\/pre>\n
Show the current date and timezone<\/h3>\n
date<\/code><\/pre>\n
timedatectl<\/code><\/pre>\n
3. Navigate the Linux filesystem<\/h2>\n
Display the current directory<\/h3>\n
pwd<\/code><\/pre>\n
List files and directories<\/h3>\n
ls<\/code><\/pre>\n
Detailed list with hidden files and readable sizes:<\/p>\n
ls -lah<\/code><\/pre>\n
Sort by modification time:<\/p>\n
ls -lath<\/code><\/pre>\n
Change directory<\/h3>\n
cd \/path\/to\/directory<\/code><\/pre>\n
Go to your home directory:<\/p>\n
cd ~<\/code><\/pre>\n
Go up one directory:<\/p>\n
cd ..<\/code><\/pre>\n
Return to the previous directory:<\/p>\n
cd -<\/code><\/pre>\n
Display a directory tree<\/h3>\n
tree -L 2 \/var\/www<\/code><\/pre>\n
The tree<\/code> package may need to be installed first.<\/p>\n
4. Create, copy, move, and delete files<\/h2>\n
Create an empty file<\/h3>\n
touch filename.txt<\/code><\/pre>\n
Create a directory<\/h3>\n
mkdir directory_name<\/code><\/pre>\n
Create nested directories:<\/p>\n
mkdir -p \/var\/www\/example.com\/public<\/code><\/pre>\n
Copy a file<\/h3>\n
cp source.txt destination.txt<\/code><\/pre>\n
Copy a directory recursively while preserving attributes:<\/p>\n
cp -a source_directory\/ destination_directory\/<\/code><\/pre>\n
Move or rename a file<\/h3>\n
mv old_name.txt new_name.txt<\/code><\/pre>\n
Move a file into another directory:<\/p>\n
mv file.txt \/path\/to\/destination\/<\/code><\/pre>\n
Delete a file interactively<\/h3>\n
rm -i filename.txt<\/code><\/pre>\n
Remove an empty directory<\/h3>\n
rmdir directory_name<\/code><\/pre>\n
Be careful with recursive deletion<\/strong>
\nCommands such as rm -rf<\/code> can permanently remove entire directories without confirmation. Verify the full path with pwd<\/code> and ls<\/code>, and confirm that a usable backup or snapshot exists before deleting production data.<\/div>\n
Create a symbolic link<\/h3>\n
ln -s \/actual\/path \/path\/to\/link<\/code><\/pre>\n
Inspect a file type<\/h3>\n
file filename<\/code><\/pre>\n
5. View and edit text files<\/h2>\n
Display the complete file<\/h3>\n
cat filename.txt<\/code><\/pre>\n
Read a long file one screen at a time<\/h3>\n
less filename.txt<\/code><\/pre>\n
Inside less<\/code>, press \/<\/code> to search, n<\/code> for the next match, and q<\/code> to quit.<\/p>\n
Show the first lines<\/h3>\n
head -n 20 filename.txt<\/code><\/pre>\n
Show the last lines<\/h3>\n
tail -n 50 filename.txt<\/code><\/pre>\n
Follow a file as new lines are added<\/h3>\n
tail -f \/var\/log\/application.log<\/code><\/pre>\n
Start with the latest 100 lines and continue following:<\/p>\n
tail -n 100 -f \/var\/log\/application.log<\/code><\/pre>\n
Edit with Nano<\/h3>\n
nano filename.txt<\/code><\/pre>\n
Edit with Vim<\/h3>\n
vim filename.txt<\/code><\/pre>\n
Write output to a file as root<\/h3>\n
echo \"configuration=value\" | sudo tee \/etc\/example.conf<\/code><\/pre>\n
Append instead of overwriting:<\/p>\n
echo \"new line\" | sudo tee -a \/etc\/example.conf<\/code><\/pre>\n
Compare two files<\/h3>\n
diff -u old.conf new.conf<\/code><\/pre>\n
6. Search for files, directories, and text<\/h2>\n
Find a file by name<\/h3>\n
find \/path\/to\/search -type f -name \"filename.conf\"<\/code><\/pre>\n
Find files case-insensitively<\/h3>\n
find \/var\/www -type f -iname \"*.php\"<\/code><\/pre>\n
Find large files<\/h3>\n
find \/var -type f -size +500M -printf '%s %p\\n' 2>\/dev\/null | sort -nr | head<\/code><\/pre>\n
Find files modified within one day<\/h3>\n
find \/var\/www -type f -mtime -1<\/code><\/pre>\n
Search for text inside a file<\/h3>\n
grep \"search text\" filename.txt<\/code><\/pre>\n
Search recursively and include line numbers<\/h3>\n
grep -Rni \"search text\" \/path\/to\/directory<\/code><\/pre>\n
Search using an extended regular expression<\/h3>\n
grep -E \"error|failed|critical\" application.log<\/code><\/pre>\n
Exclude comments and blank lines<\/h3>\n
grep -Ev '^[[:space:]]*(#|$)' \/etc\/ssh\/sshd_config<\/code><\/pre>\n
Locate a command<\/h3>\n
command -v nginx<\/code><\/pre>\n
which php<\/code><\/pre>\n
Search command history<\/h3>\n
history | grep systemctl<\/code><\/pre>\n
You can also press Ctrl+R<\/code> in Bash and begin typing part of a previous command.<\/p>\n
7. Linux permissions and ownership<\/h2>\n
View permissions and ownership<\/h3>\n
ls -l filename<\/code><\/pre>\n
Change file permissions<\/h3>\n
chmod 644 filename<\/code><\/pre>\n
Typical permissions:<\/p>\n