Structured list of essential Linux commands you need when working on servers remotely via SSH. This isn't every command under the sun, but a practical toolbox covering systemd, networking, users, permissions, files, processes, and SSH.

📘 Essential Linux Server Commands

1. SSH Basics

Connect to a server:
```
ssh user@hostname
```
Connect with a key:
```
ssh -i ~/.ssh/id_rsa user@hostname
```

Copy files to server:

scp file.txt user@hostname:/path/to/dest

Copy files from server:
```
scp user@hostname:/path/to/file.txt ./
```

Keep tunnel alive:

ssh -o ServerAliveInterval=60 user@hostname

2. System Management (systemd)

Start a service:
```
sudo systemctl start servicename
```
Stop a service:
```
sudo systemctl stop servicename
```
Restart a service:
```
sudo systemctl restart servicename
```
Enable service at boot:
```
sudo systemctl enable servicename
```
Disable service:
```
sudo systemctl disable servicename
```
Check status:
```
systemctl status servicename
```
Show logs:
```
journalctl -u servicename
```

3. Network Management (NetworkManager)

Launch TUI:
```
nmtui
```

CLI interface:

nmcli device status
nmcli connection show
nmcli device wifi list
nmcli device wifi connect "SSID" password "yourpassword"

Restart networking:
```
sudo systemctl restart NetworkManager
```

4. User Management

Add user:
```
sudo adduser username
```
Delete user:
```
sudo deluser username
```
Add user to group:
```
sudo usermod -aG groupname username
```
Change password:
```
passwd username
```
Check groups:
```
groups username
```

5. File Permissions

Change file ownership:
```
sudo chown user:group file.txt
```
Change file permissions:
```
chmod 755 script.sh
chmod 644 file.txt
```

Recursive apply:

chown -R user:group folder/
chmod -R 755 folder/

6. File & Directory Management

List files:
```
ls -lah
```
Change directory:
```
cd /path/to/dir
```
Copy:
```
cp file1 file2
cp -r dir1 dir2
```
Move/rename:
```
mv file1 file2
```
Delete:
```
rm file.txt
rm -r folder/
```

7. Package Management

Debian/Ubuntu:

sudo apt update && sudo apt upgrade
sudo apt install package
sudo apt remove package

RHEL/Fedora:

sudo dnf update
sudo dnf install package
sudo dnf remove package

Arch:

sudo pacman -Syu
sudo pacman -S package
sudo pacman -R package

8. Process & Resource Management

See running processes:
```
ps aux | grep processname
```
Kill process:
```
kill -9 PID
```
Live monitor:
```
top
htop   # (if installed)
```
Disk usage:
```
df -h
du -sh folder/
```
Memory usage:
```
free -h
```

9. Logs & Monitoring

System logs:
```
journalctl -xe
```

Follow live logs:

tail -f /var/log/syslog
tail -f /var/log/messages

Specific service logs:
```
journalctl -u ssh
```

10. Misc Essentials

Find files:
```
find / -name filename.txt
```
Search inside files:
```
grep "pattern" file.txt
```
Download file:
```
wget URL
curl -O URL
```

Tar & extract:

tar -czvf archive.tar.gz folder/
tar -xzvf archive.tar.gz

Check open ports:

ss -tulpn
netstat -tulpn   # (if installed)

souravrax/LinuxCommands.md