Hands-on Lab·Red Hat Certified System Administrator
Special Permissions: SUID, SGID and Sticky Bit
Not a separate objective, and assumed by two that are: the collaborative directory in the groups objective needs SGID, and diagnosing permissions needs you to read an s or a t where you expected an x. All three bits are set here and their effects measured with real users.
File Systems Guide 42 of 67 Intermediate
- OSRHEL 10.0
- Kernel6.12.0-55.9.1.el10_0
- dnf4.20.0
- Flatpak1.16.0
- TimeAbout 12 min
The three bits share a fourth octal digit: 4 SUID, 2 SGID, 1 sticky. chmod 2770 is SGID plus rwxrwx---. In symbolic form they are u+s, g+s and +t.
| Server Name | IP Address | OS | Roles | CPU | RAM | HDD |
|---|---|---|---|---|---|---|
| RHCSA-A01 | 192.168.0.31 | RHEL 10.0 | Practice node (graded) - spare /dev/sda | 2 Core | 4 GB | 50 GB + 15 GB |
This guide includes
Use this because it is not a separate objective and two others quietly assume it. This matters because the collaborative directory and /tmp both depend on bits that never appear in the usual rwx explanation.
- finding SUID, and the two binaries you already rely on
- using SGID on a directory
- reading the sticky bit, and why
/tmpworks the way it does
Before you start
- A sudo-capable account.
- The session reuses the users and directory from
guide 41and removes them.
-
SUID, and the two you already rely on
-
SGID on a directory
-
The sticky bit, and why `/tmp` works