DevOps · interactive
File permissions
Every file has an owner, a group, and three sets of read/write/execute bits: for the owner, for members of the group, and for everyone else. Linux checks exactly one set per user: the first that applies.
-rwxr-xr-- alice web deploy.sh
chmod 754 deploy.sh
owner (alice)
7
group (web)
5
others
4
| user | uses | read it | edit it | run it |
|---|---|---|---|---|
| alice | owner | ✓ | ✓ | ✓ |
| deploy | group | ✓ | ✗ | ✓ |
| guest | others | ✓ | ✗ | ✗ |
Each digit is r=4 + w=2 + x=1. 754 gives alice rwx, the web group r-x, everyone else r--.
Common modes
1 If you own the file, only the owner bits count; else if you're in its group, the group bits; else the others bits.
An owner can have fewer rights than others.
2 3 4
In production
Tools and technologies
Every Linux system and container uses these bits.
Not tied to one language — use these names when you search docs or design a system.