Work out the right chmod value

Convert between 755 and rwxr-xr-x in either direction, and see what each permission class can actually do before you run the command.

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The problem

Permission bugs get fixed by guessing - someone runs chmod 777, the error goes away, and a world-writable file ships to production. Reading the mode properly takes ten seconds and produces a fix that is actually correct.

Sample input

Mode from ls -l
drwxrwsr-x

Expected output

Converted mode
Octal:     2775
Symbolic:  rwxrwsr-x  (directory)
Command:   chmod 2775 directory/
Owner:     read, write, enter
Group:     read, write, enter  (setgid: new files inherit the group)
Others:    read, enter

How to do it

  1. Paste the mode - octal such as 2775, or the symbolic string from ls -l.
  2. Switch "Applies to" to directory when the target is a folder.
  3. Read what each class can do, and any warning about world-writable or setuid bits.
  4. Open the Permission matrix tab for the read/write/execute grid.
  5. Copy the generated chmod command into your terminal or playbook.

Common mistakes

  • Using 777 to make an error disappear instead of fixing ownership.
  • Leaving an SSH private key group-readable, which SSH refuses to use.
  • Setting setuid on a script, which most systems ignore for security reasons.
  • Forgetting that execute on a directory means "may enter", not "may run".

Related tools

FAQ

What is chmod 755 in symbolic form?

rwxr-xr-x - the owner can read, write and execute, while group and others can read and execute.

Which mode should a private key have?

600. SSH refuses to use a private key that is readable by the group or by other users on the machine.

What does the s in rwxrwsr-x mean?

The setgid bit. On a directory, new files inherit the directory's group, which is how a shared project folder is normally set up.

Is anything uploaded?

No. The conversion is arithmetic performed locally in your browser.

This guide uses browser-local tooling. Avoid pasting production secrets unless you understand what the tool displays and shares.

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Work out a chmod value: quick answer

Use this when a deploy step fails with "permission denied", when reviewing ls -l output in an audit, or when you need the octal value for a Dockerfile, Ansible task or Terraform resource. Read what the mode grants, then apply the narrowest value that works.

What to verify

Check whether the file needs to be executable at all, whether the group needs write access, and whether any special bit is set. A world-writable file or a setuid binary should be deliberate, never incidental.

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