Skip to main content
WebUtilsLabUseful tools, one clean workspace
WebUtilsLab Linux Tools

Linux Permission Tools

Diagnose Linux permission problems with chmod modes, umask defaults, Docker bind mounts, PUID/PGID mismatches, shared groups, setgid inheritance, and ACL checks.

Common Linux permission problems

Start with the page that matches the actual failure before changing chmod, umask, group ownership, setgid, or ACL settings. Each page focuses on a specific Linux permission problem and the commands needed to diagnose it.

Problem Start here
New files are created as 644 and another service cannot edit them Umask Calculator
Syncthing says synced, but the NAS host folder is empty Check Syncthing path mapping
Permission denied may involve mode bits, ownership, groups, umask, or ACLs Linux Permission Diagnosis
Existing files have the wrong rwx or octal mode Chmod Calculator

Linux tools

Linux

Chmod Calculator

Convert Linux file permissions into octal chmod values, symbolic rwx notation, ls-style previews, and copy-ready commands.

  • Octal and symbolic output
  • Copy-ready chmod command
Open Chmod Calculator
Linux

Umask Calculator

Calculate Linux umask results for new files and directories with octal modes, rwx output, and shared-folder guidance.

  • File and directory defaults
  • Octal and rwx output
Open Umask Calculator
Linux umask reference

All Umask Values Table

Search every Linux umask value from 000 through 777 and compare the resulting file and directory modes in one searchable reference.

  • All 512 umask values
  • Files and directories
  • Searchable reference table
Open table
Docker permission guide

Docker PUID, PGID, and UMASK Permissions

Diagnose Docker bind-mount permissions with numeric UID/GID checks, expected umask output, a complete Compose example, setgid, and ACL guidance.

  • Interactive PUID/PGID diagnostic
  • UMASK 022 vs 002 output
  • Complete Compose example
Open guide
Docker and shared folder guide

Syncthing Shared Folder Permissions

Diagnose Syncthing .stfolder, running-process groups, Docker path mappings, watcher errors, and shared-folder permissions.

  • Actual process group checks
  • Host → container → Folder Path
  • Watcher vs full-scan branch
Open guide
Command-first troubleshooting guide

Linux Permission Diagnosis

Diagnose Linux permission denied errors across current modes, ownership, groups, umask defaults, parent directories, setgid, and ACLs.

  • ls, stat, id, getfacl checks
  • chmod vs umask decision
  • Ownership, setgid, and ACL path
Open diagnosis guide
Linux permission guide

Chmod vs Umask

Decide whether a Linux permission issue should be fixed with chmod on an existing file or by changing the umask for future files.

  • Existing vs new permissions
  • 022, 644, and 755 examples
  • chmod and umask decision path
Open comparison guide

Recommended Linux permission troubleshooting order

Best starting tool: Chmod Calculator — Use it first when the target already exists and you need to convert rwx choices into an octal chmod command before changing a file or directory.

Common workflow path: Linux file permissions calculator Linux umask calculator Linux permission diagnosis Chmod vs Umask guide

Common problem solved: Fix Linux permission problems caused by existing chmod modes, default umask values, shared-folder group ownership, setgid inheritance, Docker PUID/PGID mismatches, ACL inheritance, and unsafe chmod 777 workarounds.

  1. Use Chmod Calculator when an existing file or directory has the wrong rwx, octal, setgid, sticky, or chmod 777 mode.
  2. Use Umask Calculator when new files land as 644 or new directories land as 755 and another service needs group write access.
  3. Use the Docker and shared-folder guides when PUID, PGID, UMASK, setgid, ACLs, or unsafe chmod 777 workarounds are part of the failure.

When to use these Linux tools

Existing mode checks

Calculate chmod octal values, rwx notation, setgid/sticky bits, and safe file or directory modes before copying commands into a server shell.

Future file defaults

Use the Linux umask calculator output to understand what a shell, service, or container will create by default before blaming chmod.

Shared folder permission checks

Review PUID/PGID identity, group ownership, setgid inheritance, default ACLs, and broad write permissions before applying changes.

Specific value lookups

Open the explained chmod or umask value that matches the permission you are checking.

chmod 755 chmod 644 chmod 777 chmod 600 chmod 700 chmod 400 chmod 775 umask 0022 umask 0077 umask 0027

Linux tools FAQ

What is the difference between chmod and umask?

chmod sets permissions on existing files or directories. umask subtracts permissions from the defaults used when new files and directories are created.

Is chmod 777 safe?

Usually no. It gives everyone read, write, and execute access, which is risky for shared or public systems.

Do Linux tools run server-side?

No. Permission calculations run in the browser page and do not need a server request.