Linux Permissions
Read ls output, chmod, chown, and sudo without breaking access.
- chmod
- chown
- linux permissions
- sudo
- ssh key permission
Linux Permissions
Read ls output, chmod, chown, and sudo without breaking access.
Commands
| Command | What it does |
|---|---|
ls -l | Decode rwxr-xr-x at a glance |
chmod 755 script.sh | Standard for scripts |
chmod -R 640 config/ | Readable, not executable |
chown -R app:app /srv/app | Fix ownership after root copies |
sudo !! | Re-run last command as root |
Example
chmod 600 ~/.ssh/id_ed25519
chown -R app:app /srv/appFAQ
What do 755 and 644 mean?
Octal triples for owner, group, other: 7 is rwx, 6 is rw, 5 is r-x, 4 is r. Scripts 755, data 644, keys 600.
Permission denied but the file looks fine?
Check parent directory execute bits and ownership - traversal needs execute on every ancestor.
FAQ
What do 755 and 644 mean?
Octal triples for owner, group, other: 7 is rwx, 6 is rw, 5 is r-x, 4 is r. Scripts 755, data 644, keys 600.
Permission denied but the file looks fine?
Check parent directory execute bits and ownership - traversal needs execute on every ancestor.
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