3.5 Some useful commands
This sections is a bit of a random collection of commonly used terminal commands. Many if not most are probably known to Linux users or already mentioned in other sections, so consider this a short summary of miscellaneous commands and things that would go missing when only mentioned in a specific topic someplace else.
Manage
- Instead of
su:sudo -s(su doesn't work with the root user disabled) - Monitor system resources:
top - See currently logged in users:
worw username - Check system uptime:
uptime - Memory usage:
free - Disk space:
df -h
Networking
- See IP and MAC-address:
ifconfig - See external IP:
curl icanhazip.com - See gateway:
route -n - Use netstat to see open ports:
netstat --listen - To display open ports and established TCP and UDP connections, enter:
netstat -vautn - To see full dns hostname, remove the -n flag:
netstat -vat
Updating
Update packages and OS:
sudo apt-get update
sudo apt-get dist-upgrade
Update firmware:
sudo rpi-update
User management
Add user: adduser username, edit password: passwd username
Custom commands (aliases)
Add a line to ~/.bash_aliases with a custom shortcut, e.g:
alias mycommand='~/path/runsomescript.sh arg1 arg2'
Make sure .bash_aliasses is uncommented in ~/.bashrc.
Control disk space
Check disk space available on all drives with df -h. Check the size occupied by a folder using du -sh /some/folder/ or use a wildcard to list all the content in a folder at once: du -sh /some/folder/*.
Clean disk space by removing apt-get caches and downloads, and by pruning obsolete packages:
sudo apt-get clean
sudo apt-get autoremove
/var/log/ is a common evildoer in terms of eating precious SD card disk space. To limit the size of log files, edit /etc/logrotate.conf:
- change weekly to daily
- uncomment
#compress
Startup scripts
Scripts that should run as a background daemon on each startup must go in /etc/init.d/. Such a script should be able to process 'start' and 'stop' arguments, a simple example can be found here.
Make it executable (chmod +x /etc/init.d/myscript) and make it automatically start and stop it when the system boots or shuts down, like so:
update-rc.d myscript defaults
To stop it from running automatically:
update-rc.d myscript remove
Cron
Cronjobs, tasks that are automatically repeated at set times, are explained in the section about periodic backups.