Basic Commands for Linux System Administration

Basic Commands for Linux System Administration

Linux is a powerful operating system widely used for servers, system administration, and development. Mastering its commands is essential for every system administrator. Here’s a quick guide to the most fundamental Linux commands for system administration.

1. User and Group Management

Managing users and groups is a key part of system administration.

Commands

adduser [username]: Add a new user.
```
  sudo adduser john
```
passwd [username]: Set or update a user password.
```
  sudo passwd john
```
usermod -aG [group] [username]: Add a user to a group.
```
  sudo usermod -aG sudo john
```
deluser [username]: Delete a user.
```
  sudo deluser john
```

2. File and Directory Management

Knowing how to navigate and manipulate files is crucial.

Commands

ls: List files in a directory.
```
  ls -al
```
cd [directory]: Change the current directory.
```
  cd /etc
```
cp [source] [destination]: Copy files or directories.
```
  cp file.txt /home/user/
```
mv [source] [destination]: Move or rename files.
```
  mv file.txt renamed_file.txt
```
rm [file/directory]: Delete files or directories.
```
  rm -rf folder/
```

3. Disk and Filesystem Management

Monitoring and managing disk usage ensures optimal performance.

Commands

df -h: Show disk space usage.
```
  df -h
```
du -sh [directory]: Show directory size.
```
  du -sh /var/log
```
mount [device] [mountpoint]: Mount a filesystem.
```
  sudo mount /dev/sda1 /mnt
```
umount [mountpoint]: Unmount a filesystem.
```
  sudo umount /mnt
```
lsblk: List information about block devices.
```
  lsblk
```

4. Process and System Monitoring

Monitoring system performance is vital for troubleshooting.

Commands

top: Display active processes and resource usage.
```
  top
```
ps aux: View details about running processes.
```
  ps aux
```
kill [PID]: Terminate a process by PID.
```
  kill 1234
```
uptime: Display how long the system has been running.
```
  uptime
```

5. Network Management

Network troubleshooting is essential for connectivity issues.

Commands

ip a: Display IP address information.
```
  ip a
```
ping [hostname/IP]: Test connectivity.
```
  ping google.com
```
netstat -tuln: Show open ports and services.
```
  netstat -tuln
```
ss -tulwn: Modern alternative to netstat.
```
  ss -tulwn
```
scp [source] [user@destination]:[path]: Copy files securely between systems.
```
  scp file.txt user@remote:/home/user/
```

6. Service Management

Start, stop, and monitor services on the system.

Commands

systemctl start [service]: Start a service.
```
  sudo systemctl start apache2
```
systemctl stop [service]: Stop a service.
```
  sudo systemctl stop apache2
```
systemctl status [service]: Check the status of a service.
```
  sudo systemctl status apache2
```
systemctl enable [service]: Enable a service to start on boot.
```
  sudo systemctl enable apache2
```
systemctl disable [service]: Disable a service from starting on boot.
```
  sudo systemctl disable apache2
```

7. Log Management

Logs provide critical insights into system activity.

Commands

cat /var/log/[logfile]: View logs.
```
  cat /var/log/syslog
```
tail -f /var/log/[logfile]: Monitor live logs.
```
  tail -f /var/log/syslog
```
journalctl -u [service]: View logs for a specific service.
```
  journalctl -u apache2
```

Conclusion

Mastering these basic Linux commands will build a strong foundation for system administration. Regular practice will enhance your efficiency in managing systems.