Tick the permissions you want and read off the octal number and chmod command, or type an octal value like 755 to see what it allows.
| Read | Write | Execute | |
|---|---|---|---|
| Owner | |||
| Group | |||
| Others |
Common presets:
chmod 644 file.txt
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Each permission has a value: read is 4, write is 2 and execute is 1. Add them for each of the three classes — owner, group, others. 7 is read, write and execute; 6 is read and write; 5 is read and execute; 4 is read only. So 755 means the owner can do everything while everyone else can read and run, and 644 is the standard for ordinary files.
A fourth leading digit sets setuid (4), setgid (2) and the sticky bit (1). The sticky bit on a shared directory such as /tmp stops users deleting each other's files. As a rule, use 644 for files, 755 for directories and scripts, and 600 or 700 for anything private such as SSH keys. Avoid 777 on servers — it lets any user on the machine modify the file.
📖 Read the full guide: Linux File Permissions and chmod Explained
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It gives read, write and execute permission to the owner, the group and everyone else. It's almost never the right fix for a permissions problem and is a security risk on shared or internet-facing servers.
755 adds the execute bit for everyone, needed to run a script or enter a directory. 644 is read/write for the owner and read-only for others, suited to ordinary files.
A capital S or T in symbolic form means setuid/setgid/sticky is set but the matching execute bit is not.