FREE LINUX REFERENCE
Linux permissions cheat sheet
Understand the bits instead of memorizing commands without context.
r = 4
Read permission.
w = 2
Write permission.
x = 1
Execute; on directories, traversal/search.
chmod 750 file
Owner rwx (7), group r-x (5), others --- (0).
chown user:group file
Change owner and group.
umask
Influences permissions removed from defaults when new objects are created.
Sticky bit
On shared directories, helps prevent users from deleting or renaming files they do not own.
setgid directory
New files commonly inherit the directory's group.
Quick method: read permissions left to right as owner, group, others. Convert each rwx triplet independently.