System
uname- Displays all system information.
hostname- Shows current hostname and related details.
uptime- Shows how long the system has been running.
timedatectl status- Shows system time.
System monitoring and management
top- Displays real-time system processes.
htop- An interactive process viewer (needs installation).
df -h- Shows disk usage in a human-readable format.
free -h- Displays free and used memory in MB.
kill <pid>- Terminates a process.
Running commands
command &- Runs command in the background.
jobs- Displays background commands.
fg <command number>- Brings command to the foreground.
Service management
sudo systemctl start <service>- Starts a service.
sudo systemctl stop <service>- Stops a service.
sudo systemctl status <service>- Checks the status of a service.
sudo systemctl reload <service>- Reloads a service configuration without stopping its operation.
journalctl -f- Follows the journal, showing new log messages in real time.
journalctl -u <unit_name>- Displays logs for a specific systemd unit.
Cron jobs and scheduling
crontab -e- Edits cron jobs for the current user.
crontab -l- Lists cron jobs for the current user.
Files
File management
ls- Lists files and directories.
touch <filename>- Creates an empty file or updates the last accessed date.
cp <source> <destination>- Copy a file to destination, or multiple files to a directory
mv <source> <destination>- Moves files or renames them.
rm <file>- Deletes a file. Use rm -r to delete directories.
Directory navigation
pwd- Displays the current directory path.
cd <directory>- Changes the current directory.
mkdir <dirname>- Creates a new directory.
File permissions and ownership
chmod [who][±][perm] <file>- Changes file permissions.
chmod u+x <file>- Makes a file executable by its owner.
chown [user]:[group] <file>- Changes file owner and group.
Searching and finding
find [path] -name <search_pattern>- Finds files and directories.
grep <search_pattern> <file>- Searches for a pattern in files.
Archiving and compression
tar -czvf <n>.tar.gz [files]- Compresses files into a tar.gz archive.
tar -xvf <n>.tar.gz[.bz2] [destination]- Extracts a compressed archive.
Text editing and processing
nano <file>- Opens a file in the Nano text editor.
cat <file>- Displays the contents of a file.
less <file>- Displays the paginated content of a file.
head <file>- Shows the first several lines.
tail <file>- Shows the last several lines.
awk '{print}' <file>- Prints every line in a file.
