Linux File Links and Permissions/shaare/y0lAmg
Links
Soft Link (Symbolic Link)
ln -s- Link will be removed if the original file is removed or renamed.
Hard Link
ln- Deleting, renaming, or moving the original file will not affect the hard link.
Diagram
INODE
↑
MY HARD LINK ← MYFILE.TXT → MY-SOFT-LINKCommand to check links:
ls -lTriFile Permissions
Permission Types
| Symbol | Permission | Example (Mnemonic) |
|---|---|---|
| R | Read | Riri (4) |
| W | Write | Winnie (2) |
| X | Execute | Xena (1) |
Each Permission (R, W, X) Can Be Controlled at Three Levels
- U → User
- G → Group
- O → Others (Everyone)
Permission Strings
Example:
-rwxrwxrwx
| | |
| | └── Others
| └───── Group
└───────── UserTo remove write permission from all:
chmod a-w filenameTo add read and write permission for user:
chmod u+rw filenameDirectory Permissions
Example:
drwxrwxrwx
^ ^ ^
| | └── Others
| └───── Group
└───────── UserNumeric Permission Mapping
| Value | Permissions | Symbol | Mnemonic |
|---|---|---|---|
| 0 | No permission | --- | |
| 1 | Execute | --x | Xena |
| 2 | Write | -w- | Winnie |
| 3 | Execute + Write | -wx | |
| 4 | Read | r-- | Riri |
| 5 | Read + Execute | r-x | |
| 6 | Read + Write | rw- | |
| 7 | Read + Write + Exec | rwx |
Example to set permissions:
chmod 764 fileBreakdown:
- User (7) → rwx
- Group (6) → rw-
- Others (4) → r--
(19)