Server Operations Reference

Common Linux Server Commands

A practical quick-reference guide for common Linux server administration tasks: navigating the filesystem, checking services, reviewing logs, monitoring usage, managing packages, and troubleshooting everyday issues.

1. Navigation & Filesystem Basics

Command	What It Does
`pwd`	Show the current directory path.
`ls`	List files in the current directory.
`ls -la`	List all files, including hidden ones, with details.
`cd /path/to/folder`	Change to a specific directory.
`cd ~`	Go to the current user’s home directory.
`cd ..`	Move up one directory level.
`tree`	Display folders/files in a tree structure if installed.

2. Files & Directories

Command	What It Does
`mkdir foldername`	Create a new directory.
`touch filename.txt`	Create an empty file.
`cp file1 file2`	Copy a file.
`cp -r dir1 dir2`	Copy a directory recursively.
`mv oldname newname`	Rename or move a file.
`rm filename`	Delete a file.
`rm -r foldername`	Delete a directory recursively.
`find /path -name "filename"`	Search for a file by name.
`locate filename`	Quickly find files if locate database is available.

3. File Viewing & Editing

Command	What It Does
`cat filename`	Print a file’s contents.
`less filename`	View a file one screen at a time.
`head filename`	Show the first lines of a file.
`tail filename`	Show the last lines of a file.
`tail -f /var/log/syslog`	Follow a log file in real time.
`nano filename`	Edit a file with Nano.
`vim filename`	Edit a file with Vim.
`grep "text" filename`	Search for text inside a file.
`grep -R "text" /path`	Search recursively through files.

4. Permissions & Ownership

Command	What It Does
`chmod 644 file`	Set standard read/write permissions for a file.
`chmod 755 directory`	Set standard executable directory permissions.
`chown user:user file`	Change file owner and group.
`chown -R user:user folder`	Change ownership recursively.
`ls -l`	View permissions, owners, and groups.

5. Processes & System Monitoring

Command	What It Does
`top`	Live view of running processes and resource usage.
`htop`	Enhanced process viewer if installed.
`ps aux`	List all running processes.
`ps aux \| grep nginx`	Find a running process by name.
`kill PID`	Terminate a process by PID.
`kill -9 PID`	Force kill a stuck process.
`uptime`	Show uptime and system load.
`free -h`	Display memory usage in human-readable format.
`vmstat`	Show system performance stats.

6. Services & systemd

Command	What It Does
`systemctl status nginx`	Check service status.
`systemctl restart nginx`	Restart a service.
`systemctl reload nginx`	Reload config without full restart if supported.
`systemctl stop nginx`	Stop a service.
`systemctl start nginx`	Start a service.
`systemctl enable nginx`	Enable service at boot.
`systemctl disable nginx`	Disable service at boot.
`journalctl -u nginx`	Show logs for a specific service.
`journalctl -xe`	View recent systemd-related errors.

7. Logs

Command	What It Does
`tail -f /var/log/syslog`	Watch general system logs live.
`tail -f /var/log/auth.log`	Watch authentication/login attempts.
`journalctl -f`	Follow systemd journal in real time.
`journalctl --since "1 hour ago"`	Show logs from the last hour.
`dmesg \| tail`	View recent kernel messages.

8. Networking

Command	What It Does
`ip a`	Show IP addresses and interfaces.
`ip route`	Show routing table.
`ping 8.8.8.8`	Test connectivity to a remote host.
`ss -tulpn`	Show listening ports and associated processes.
`curl ifconfig.me`	Show public IP address.
`curl -I https://example.com`	Fetch only HTTP headers from a site.
`wget URL`	Download a file from the command line.
`nslookup domain.com`	Check DNS resolution.
`dig domain.com`	Detailed DNS lookup.

9. Disk & Storage

Command	What It Does
`df -h`	Show disk usage by mounted filesystem.
`du -sh *`	Show size of items in current directory.
`du -sh /path/to/folder`	Show total size of a folder.
`lsblk`	List block devices and partitions.
`mount`	Show mounted filesystems.

10. Users & Identity

Command	What It Does
`whoami`	Show current user.
`id`	Show user and group IDs.
`who`	Show logged-in users.
`last`	Show login history.
`passwd`	Change current user password.
`sudo -i`	Open a root shell if sudo is permitted.

11. Packages & Updates

Debian / Ubuntu:

Command	What It Does
`sudo apt update`	Refresh package lists.
`sudo apt upgrade`	Install available upgrades.
`sudo apt install package-name`	Install a package.
`sudo apt remove package-name`	Remove a package.
`sudo apt autoremove`	Remove unused dependencies.

RHEL / CentOS / Fedora:

Command	What It Does
`sudo dnf check-update`	Check for updates.
`sudo dnf upgrade`	Install updates.
`sudo dnf install package-name`	Install a package.
`sudo dnf remove package-name`	Remove a package.

12. Archives & Compression

Command	What It Does
`tar -czf archive.tar.gz folder/`	Create a compressed tar archive.
`tar -xzf archive.tar.gz`	Extract a compressed tar archive.
`zip -r archive.zip folder/`	Create a ZIP archive.
`unzip archive.zip`	Extract a ZIP archive.

13. Use With Caution

rm -rf foldername — Force delete recursively. Double-check before running.
kill -9 PID — Force kill a process immediately.
chmod -R 777 folder — Generally unsafe on production systems.
chown -R user:user / — Catastrophic if used incorrectly.
dd — Powerful disk utility; mistakes can destroy data.
reboot / shutdown -h now — Only use when appropriate.