World-writable files let any local account or compromised process alter them, often escalating to code execution. Use minimal modes and correct ownership instead.

Why do directories need the execute bit?

Execute on directories grants traverse permission; without it you cannot `cd` or access children even when files inside are readable. Files use execute for binaries and scripts.

What do setuid and sticky mean?

Setuid runs executables with owner privileges; sticky on shared directories restricts deletes to owners. Misconfigurations are privilege-escalation risks—apply deliberately.

Chmod Permission Calculator

POSIX permissions combine user/group/other bits with read, write, and execute plus optional setuid/setgid/sticky flags. Visual calculators prevent accidental world-writable deployments and clarify automation templates for newcomers.

How to use

Start from `ls -l` output or an infrastructure definition you must mirror exactly.
Toggle class bits or enter an octal like `0755`; note how symlinks versus targets inherit modes differently.
Apply with `chmod` in staging, rerun smoke tests, and favor least privilege—especially on deploy keys and cron scripts.

FAQ

Why avoid 777?: World-writable files let any local account or compromised process alter them, often escalating to code execution. Use minimal modes and correct ownership instead.
Why do directories need the execute bit?: Execute on directories grants traverse permission; without it you cannot `cd` or access children even when files inside are readable. Files use execute for binaries and scripts.
What do setuid and sticky mean?: Setuid runs executables with owner privileges; sticky on shared directories restricts deletes to owners. Misconfigurations are privilege-escalation risks—apply deliberately.

Chmod Permission Calculator

How to use

FAQ

Linux Chmod 权限计算器