What permissions should /dev/mem have?

[stryktips]

Hi,

In an attempt to solve a problem I had, I changed the permissions on /dev/mem to 666. Now I want to reset it back to the way it was. What permissions is it supposed to have?

/Janne

[Paeryn]

660 I would assume, root user and group has read/write permission.

[DirkS]

660 I would assume, root user and group has read/write permission.

Code: Select all

pi@raspi2b:~$ stat /dev/mem
  File: ‘/dev/mem’
  Size: 0               Blocks: 0          IO Block: 4096   character special file
Device: 6h/6d   Inode: 1028        Links: 1     Device type: 1,1
Access: (0640/crw-r-----)  Uid: (    0/    root)   Gid: (   15/    kmem)

[Paeryn]

Ah, I stand corrected. I was going from memory, I was sure in the past (going back well before RPi days) it was 660... I just checked the man pages and that says that typically it's 660 for /dev/mem and 640 for /dev/kmem (though /dev/kmem is rarely used nowadays).

[stryktips]

Thanks!

[jojopi]

This is rather moot. Permissions in /dev do not survive a reboot, and changing the permissions on /dev/mem does not actually grant any access to unprivileged users.