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Linux Permissions and Links Cheat Sheet

Linux Permissions and Links•Permalink

Change permissions, ownership, umask, and symbolic or hard links on Linux.

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chmod Basics

Add execute permission for user

Grant user execute permission.

↗#
bashANYchmodpermissions
bash
chmod u+x script.sh

Set file to 644

Common mode for normal text or config files.

↗#
bashANYchmodoctal
bash
chmod 644 config.ini

Set file or directory to 755

Common executable/script or directory mode.

↗#
bashANYchmodoctal
bash
chmod 755 deploy.sh

Change permissions recursively

Apply mode changes to a directory tree.

↗#
bashANYchmodrecursivedirectories
bash
chmod -R u=rwX,go=rX project

Ownership and umask

Change owner and group

Set file owner and group together.

↗#
bashANYchownownership
bash
sudo chown alice:developers app.log

Recursively change ownership

Update owner and group across a tree.

↗#
bashANYchownrecursive
bash
sudo chown -R www-data:www-data /var/www/app

Change group

Set a file's group without changing owner.

↗#
bashANYchgrpgroup
bash
chgrp developers shared.txt

Show and set umask

Inspect and change default permission mask.

↗#
bashANYumaskpermissions
bash
umask && umask 027

Special Permission Bits

Set setuid bit

Set executable to run with owner's effective UID.

↗#
bashANYchmodsetuidsecurity
bash
chmod u+s binary

Set setgid on directory

New files inherit directory group.

↗#
bashANYchmodsetgiddirectories
bash
chmod g+s shared-dir

Set sticky bit on directory

Allow only owners/root to delete their own files.

↗#
bashANYchmodsticky-bitdirectories
bash
chmod +t /shared/tmp

Links and Link Recipes

Replace symlink atomically-ish

Create or update a symlink target with force.

↗#
bashANYlnsymlinkdeploy
bash
ln -sfn /opt/releases/2026-03-07 current

Find files sharing same inode count

Inspect hard link count with ls/stat.

↗#
bashANYhard-linkfindinode
bash
find . -type f -links +1 -ls

Inspect path components

Resolve each path component and symlink along the path.

↗#
bashANYpathssymlinkinspection
bash
namei -l /var/www/current/public

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