Free Ubuntu Tools

These tools do the small pieces of arithmetic that come up again and again on the Ubuntu command line. Each one runs entirely in your browser, shows the rules it follows and links the Ubuntu manual pages those rules come from.

Work out file permissions with the chmod calculator. It converts between octal modes such as 755 and the rwxr-xr-x form that ls -l prints, accepts symbolic modes like u=rwx,go=rx, handles the setuid, setgid and sticky bits, and shows what a umask does to new files and directories. Schedule a recurring job with the cron expression builder, which turns a preset or your own five fields into a crontab line, explains it in plain English, warns about an unescaped percent sign and lists the next run times.

The rules come from the Ubuntu manual pages for chmod(1), umask(2), mkdir(1), crontab(5) and crontab(1), as read on 13 November 2026. If a page here disagrees with the manual on your own release, tell us through the contact page.