developer4 sections · 24 items

Chmod Permission Reference Cheat Sheet

Linux/Unix file permission notation, common chmod values with use cases, and symbolic vs. numeric permission modes.

Permission Bits

Item	Value	Notes
Read (r)	4	View file content / list directory
Write (w)	2	Modify file / add/remove in directory
Execute (x)	1	Run file / access directory
No permission	0	Represented as -
Format	Owner \| Group \| Others	e.g., 755 = rwxr-xr-x

Item	Value	Notes
755	rwxr-xr-x	Standard for directories & scripts
644	rw-r--r--	Standard for files (HTML, CSS, images)
700	rwx------	Private directory, owner only
600	rw-------	Private file (SSH keys, .env)
777	rwxrwxrwx	Full access for all — AVOID in production
664	rw-rw-r--	Owner & group can edit, others read
750	rwxr-x---	Owner full, group read/exec, others none
444	r--r--r--	Read-only for everyone

Item	Value	Notes
Add execute for owner	chmod u+x file	--
Remove write for others	chmod o-w file	--
Set group read+write	chmod g=rw file	--
Add execute for all	chmod a+x file	a = all (u+g+o)
Recursive directory	chmod -R 755 directory/	Apply to all contents
Copy permissions	chmod --reference=source target	Match another file

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