Stage 4 · Lesson 1 of 8
Read, write and execute permissions
Every file has an owner, a group and a set of . The bits say what three kinds of people may do: the owning user, members of the group, and everyone else. ls -l shows them as something like rwxr-xr--.
Read it in threes: read, write and execute for the user, then the group, then others. On a folder, execute means you are allowed to enter it. changes these bits. chmod +x script.sh makes a script runnable.
Numbers are a common shorthand: 644 is usual for files and 755 for scripts. refuses to use a that other people can read, so chmod 600 matters there.
Common trap"fixing" a permission error with chmod 777, which lets anyone change the file and hides the real problem.
A question to check yourself, an AI practice session and 2 cheat sheet entries come when you add the roadmap to your account. Add it
Resources for this stage
Start with· follow one of these
- BookFreeThe Linux Command Line
William Shotts · Beginner
Its chapters on permissions and processes are the clearest free explanation of this stage
- GuideFreeThe Linux Command Line for Beginners (Ubuntu)
Canonical · Beginner
Includes a short, careful section on the superuser and when to use sudo
Practise
Keep handy
Also worth your time
- roadmap.sh: LinuxGo deeper
See the users, permissions and process management branches of the Linux map