Common Linux terminal commands

Favorite Linux commands

ls -List files and ddirectories. Use the -la flag for more details
cd [directory] - Change directory. This command can also be used double dots to go back one level cd .. or with dash cd - to go back to previous directory. cd ~ or cd to get to HOME directory and cd / to get to root directory.
mkdir [directory] -Make directory
rm [file | directory] removes a file of directory. If the directory is not empty. use the recursive flag -r
CTRL+l -Clear screen
CTRL+r -Find a previous command. Hit CTRL+r and start typing to find a command you have used before
whoami -Show the current user
sudo [command] -Run command as root
sudo su -Change user to root
find -name [name of file] -Find a file by name
grep -R ./ -e "[seach pattern]" -find files containing a word or pattern
cat [file name] -View content of file
df -h -shows available and used disk space on the Linux system
lsblk -List information about block devices and partitions
chmod +x [file name] -Makes file executable
grep - is used to filter output such as df -h | grep udev returns only one row from the df command
asw - spits an input into an array. For instance df -h | grep udev | awk '{print $2}' returns only the second column.

grep and awk sample

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            315M     0  315M   0% /dev
tmpfs            91M  1.2M   90M   2% /run
/dev/mmcblk0p2   29G  4.8G   22G  18% /
tmpfs           454M  8.0K  454M   1% /dev/shm
tmpfs           5.0M   12K  5.0M   1% /run/lock
/dev/mmcblk0p1  510M   75M  436M  15% /boot/firmware
tmpfs            91M   44K   91M   1% /run/user/1000

 $ df | grep udev
udev              322452       0    322452   0% /dev

$ df | grep udev | awk '{print $2}'
322452

Favorite vi commands

vi or vim is a commonly used file editor, which can be complex to use, but here are a few commands to get you started.

To open a file with vi, type vi [file name]
To edit the content, hit i
To delete a row, hit d+d
To leave a mode (such as edit), hit ESC+ESC
To save your changes, hit w
To quit vi, hit w or wq to save and quit

Favorite less commands

less is a great tool for analyzing log files.

Open a log file, use sudo less /var/log/syslog. Use the -S flag to wrap long lines`
Use b to go backward one window
Use f to go forward one window
Use G to go to the end of file
Use g to go to the beginning of file
Use / to search forward
Use ? to search backward

Favorite systemctl commands

systemd is a software suite that provides an array of system components for Linux operating systems, such as daemons (services). systemctl is the tool you use to interact with systemd

systemctl start [daemon] starts a daemon
systemctl stop [daemon] stops a daemon
systemctl restart [daemon] re-starts a daemon
systemctl cat [daemon] view the service file
systemctl daemon-reload applies changes made to any service file.

Favorite journalctl commands

journalctl is also part of the systemd suite and helps you view logfile in real-time.
journalctl -u [service] -n [number of previous lines] -f .

E.g.

journalctl -u microservicebus-node -n 100 -f

journalctl --since [date] show logs from specified date
journalctl --until [date] show logs until specified date