Linux Extended permissions

Extended permissions include S,g,t

1. For creating a file or folder by the Umask value to determine the common default permissions for normal users The default is 0002 root is 0022
2. The default permissions for the directory are 777-umask (normal user 775 root is 755) The default permissions for files are 666-umask (normal user 664)
3. Special permissions suid sgid sticky
4. Suid an X-bit that does not affect the directory for the user who owns the file will change to S, such as passwd
5. Sgid is executed as the file belongs to the group, and the owning group of any new file created for the directory is the same as the group in which the directory belongs to the x in the G-bit.
6. Sticky only users who have write access to the directory can delete files they own and cannot delete files owned by other users
7. Set suid chmod u+s file name (usually set to executable file) with the number 4 position in the preceding example of Ugo 4755
8. Set Sgid chmod g+s file (clamp) name with number 2 Ibid.
9. Set sticky chmod o+t folder with number 1 Ibid.

Linux Extended permissions