File system permissions controls the ability of the users to view, change, navigate, and execute the contents of the file system.
Objetives
edit- Understand and format file systems
- Understand file systems permissions
- Understand setuid and setgid bits
- Learn chmod commands:
chmod ug+s
Setuid
editsetuid and setgid (short for "set user ID" and "set group ID")[1] are Unix access rights flags that allow users to run an executable with the permissions of the executable's owner or group respectively and to change behaviour in directories.
The setuid
and setgid
flags only have effect on binary executable files. Set these bits on scripts, like bash, perl or python do not have any effect.[1]
chmod examples
editchmod ug+s file.txt
Before: ls -la file.txt -rwxr-xr-x 1 root root 31 Nov 27 11:34 file.txt stat file.txt File: file.txt Size: 31 Blocks: 8 IO Block: 4096 regular file Device: fd00h/64768d Inode: 13 Links: 1 Access: (0755/-rwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2019-11-27 11:34:54.610196393 +0400 Modify: 2019-11-27 11:34:49.662193415 +0400 Change: 2019-11-27 11:34:49.666193418 +0400 Birth: - chmod ug+s file.txt After: ls -la file.txt -rwsr-sr-x 1 root root 31 Nov 27 11:34 file.txt stat file.txt File: file.txt Size: 31 Blocks: 8 IO Block: 4096 regular file Device: fd00h/64768d Inode: 13 Links: 1 Access: (6755/-rwsr-sr-x) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2019-11-27 11:34:54.610196393 +0400 Modify: 2019-11-27 11:34:49.662193415 +0400 Change: 2019-11-27 12:11:20.637362248 +0400 Birth: -
Hidden and system attributes
editLinux does not regard file systems' hidden and system attributes like Windows does. Instead, file and directory entry names starting with a dot (.
) are considered hidden, and can optionally be set to be revealed in file managers and command line tools.
See also
editstat
command- Filesystems
- CompTIA IT Fundamentals/File Systems