Use chmod to change permissions on a file or directory that already exists. Use umask to control the defaults used when a process creates new files or directories. This page is the quick comparison; use the diagnostic guide when ownership, groups, parent directories, setgid, or ACLs are also involved.
chmod sets a permission mode now, such as chmod 755 public_html or chmod 644 index.html. umask subtracts permission bits from the default creation mode, so umask 022 usually creates files 644 and directories 755.
| Question | Use chmod | Use umask |
|---|---|---|
| What does it affect? | Existing files and directories. | New files and directories created after the umask is set. |
| Typical command | chmod 755 folder_name |
umask 022 |
| Best for | Fixing a current file mode, deploy asset, script, static file, or private directory. | Controlling what a shell, service account, deployment process, or container creates by default. |
| What it does not do | It does not change ownership. Use chown for owner or group changes. |
It does not retroactively change existing files. Use chmod for that. |
Set umask before creating new files or directories when the default mode is the real problem.
With umask 022, app.log is usually created as 644, while uploads is usually created as 755.
If the file already exists, changing umask will not update that file. Use chmod when you need to change the actual permission bits now.
chmod 600 makes the existing file owner-readable and owner-writable, with no group or public access.
chmod sets the read, write, and execute bits for owner, group, and others. The common octal values are built from read 4, write 2, and execute 1.
chmod 755 public_html lets the owner write while group and public can read and enter the directory.chmod 644 index.html keeps a public static file readable but not executable.chmod 700 ~/.ssh keeps a private directory owner-only.Use the Chmod Calculator to convert rwx choices into octal values and copy-ready commands.
umask removes permissions from the maximum default modes. New files usually start from 666, and new directories start from 777. That is why execute bits are common on directories but not on newly created regular files.
umask 022 removes write for group and others.umask 027 removes public access and limits group write.umask 077 makes new files and directories owner-only.Use the Umask Calculator to preview file and directory results before changing shell or service defaults.
| Umask | New files | New directories | Common use |
|---|---|---|---|
0022 / 022 |
644 / -rw-r--r-- |
755 / drwxr-xr-x |
Standard public-readable files and traversable directories. |
0002 / 002 |
664 / -rw-rw-r-- |
775 / drwxrwxr-x |
Shared group workspaces where group write is expected. |
0027 / 027 |
640 / -rw-r----- |
750 / drwxr-x--- |
Limited group access with no public access. |
0077 / 077 |
600 / -rw------- |
700 / drwx------ |
Private owner-only files and directories. |
| Octal | rwx | Meaning |
|---|---|---|
0 | --- | No permissions. |
1 | --x | Execute only. |
2 | -w- | Write only. |
3 | -wx | Write and execute. |
4 | r-- | Read only. |
5 | r-x | Read and execute. |
6 | rw- | Read and write. |
7 | rwx | Read, write, and execute. |
| Mode | Typical meaning |
|---|---|
755 | Owner can write; group and others can read and execute. |
644 | Owner can write; group and others can read a regular file. |
700 | Owner-only directory or private executable script. |
600 | Owner-only private file such as a secret or key material. |
777 | Everyone can read, write, and execute. Avoid on shared systems. |
When you need files 644 and directories 755 after a bad recursive permission change, apply different modes to files and directories instead of running one broad command over everything.
Check whether the problem is an existing mode or a default creation mode. If a file already exists with the wrong mode, use chmod. If every new file created by a process has the wrong mode, check umask.
No. chmod changes permissions on existing files or directories, while umask controls default permissions for newly created files and directories.
New files usually start from 666 and new directories start from 777. umask 022 removes write permission for group and others, resulting in files 644 and directories 755.
No. umask only affects files and directories created after the umask is set. Use chmod to change files or directories that already exist.
chmod 755 sets an existing file or directory to rwxr-xr-x. umask 022 controls future creation defaults, usually producing files 644 and directories 755.
Usually no. chmod 777 grants read, write, and execute access to everyone, which is risky on shared or public systems.
No. chmod changes permission bits. Use chown when you need to change the user or group owner.