FREE CHEAT SHEET
Linux commands worth knowing
A fast reference for Linux administration and troubleshooting practice.
| Task | Command | Purpose |
|---|---|---|
| System info | uname -a | Kernel and system information |
| Disk free | df -h | Filesystem capacity |
| Directory usage | du -sh * | Find space consumers |
| Memory | free -m | RAM and swap usage |
| Processes | ps aux | Process listing |
| Live processes | top | CPU/memory activity |
| Service state | systemctl status NAME | Inspect a systemd unit |
| Journal | journalctl -u NAME | Review service logs |
| Interfaces | ip addr | Addresses and link state |
| Routes | ip route | Routing table |
| Sockets | ss -tuln | Listening TCP/UDP sockets |
| Permissions | chmod | Change permission bits |
| Ownership | chown | Change owner/group |
| Search text | grep | Match patterns |
| Find files | find | Search paths by criteria |
| Follow log | tail -f FILE | Watch appended log lines |
| Block devices | lsblk | Inspect disks and partitions |
| Mounts | mount | Show mounted filesystems |
| SELinux mode | getenforce | Check enforcement state |
| Connectivity | ping HOST | Test ICMP reachability when allowed |