# /dev/null or /dev/urandom with wrong perms 0660 after reboot **URL:** \ **Category:** SLES Configure-Administer\ **Created:** [March 23, 2016, 9:29am UTC](https://forums.suse.com/t/dev-null-or-dev-urandom-with-wrong-perms-0660-after-reboot/28021 "2016-03-23T09:29:46Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![gurucubano](https://avatars.discourse-cdn.com/v4/letter/g/b9e5f3/32.png) [@gurucubano](https://forums.suse.com/u/gurucubano)\ **Post date:** [March 23, 2016, 9:29am UTC](https://forums.suse.com/t/dev-null-or-dev-urandom-with-wrong-perms-0660-after-reboot/28021/1 "2016-03-23T09:29:46Z")
Hello, From time to time we run into the problem that /dev/urandom (and also /dev/null) has wrong perms after system boot `sisis@sunny1:> ls -l /dev/urandom crw-rw---- 1 root root 1, 9 22. Mär 10:23 /dev/urandom` and causing all kinds of, for example SSL problems. The fix is simple, but why happens this at all? I checked already all start scripts we provide and which are called at boot time without any luck. Don Google shows, that we are not allone with this, but I have found only pointers to Ubuntu systems. I have seen this inhouse on some of our SLES 11 development servers and some day ago as well on a server of one of our customers. Any ideas? Thanks in advance Matthias ---
**Author:** ![Jens-U](https://avatars.discourse-cdn.com/v4/letter/j/d78d45/32.png) [@Jens-U](https://forums.suse.com/u/Jens-U)\ **Post date:** [March 23, 2016, 3:37pm UTC](https://forums.suse.com/t/dev-null-or-dev-urandom-with-wrong-perms-0660-after-reboot/28021/2 "2016-03-23T15:37:28Z")
Hi Matthias, have you checked for according definitions in /etc/permissions.d/_? Or maybe there’s a hit in /etc/permissions_… Regards, Jens ---
**Author:** ![gurucubano](https://avatars.discourse-cdn.com/v4/letter/g/b9e5f3/32.png) [@gurucubano](https://forums.suse.com/u/gurucubano)\ **Post date:** [March 23, 2016, 3:58pm UTC](https://forums.suse.com/t/dev-null-or-dev-urandom-with-wrong-perms-0660-after-reboot/28021/3 "2016-03-23T15:58:48Z")
[QUOTE=jmozdzen;31999]Hi Matthias, have you checked for according definitions in /etc/permissions.d/_? Or maybe there’s a hit in /etc/permissions_… Regards, Jens[/QUOTE] Hello, no luck: `fgrep null /etc/permission*/* /etc/permission* /etc/permissions:/dev/null root:root 666 /etc/permissions:/lib/udev/devices/null root:root 0666 /etc/permissions:/var/lib/named/dev/null root:root 0666` This would also not explain, why it is only sometimes (very seldom, 2-3 a yearü, IIRC). Thanks matthias ---
**Author:** ![Jens-U](https://avatars.discourse-cdn.com/v4/letter/j/d78d45/32.png) [@Jens-U](https://forums.suse.com/u/Jens-U)\ **Post date:** [March 23, 2016, 5:29pm UTC](https://forums.suse.com/t/dev-null-or-dev-urandom-with-wrong-perms-0660-after-reboot/28021/4 "2016-03-23T17:29:49Z")
Hi Matthias, can you pinpoint _when_ this happens? It might be worth to correlate this with package installations (i.e. via /var/log/zypp/history) to see if some post-install script causes these changes. Regards, Jens ---
**Author:** ![gurucubano](https://avatars.discourse-cdn.com/v4/letter/g/b9e5f3/32.png) [@gurucubano](https://forums.suse.com/u/gurucubano)\ **Post date:** [March 29, 2016, 4:03pm UTC](https://forums.suse.com/t/dev-null-or-dev-urandom-with-wrong-perms-0660-after-reboot/28021/5 "2016-03-29T16:03:21Z")
[QUOTE=jmozdzen;32009]Hi Matthias, can you pinpoint _when_ this happens? It might be worth to correlate this with package installations (i.e. via /var/log/zypp/history) to see if some post-install script causes these changes. Regards, Jens[/QUOTE] As often, the problem was a mixture of two or more. The /dev/urandom modification was caused by a wrong udev-rule. The /dev/null was more sofisticated. I identified the start script (launched at system boot as user root); the script, which brings up one of our application servers, could even modify the permissions of /dev/null when started by a normal user; this is ofc impossible for this proc. But, the proc was doing syslog with facility local5 and someone configured in /etc/syslog-ng/\*.conf as target file /dev/null; a strace shows that the syslog-ng was changing the perms of the file: `# cat /tmp/syslog-ng.tr ... 3088 open("/dev/null", O_WRONLY|O_CREAT|O_NOCTTY|O_APPEND|O_NONBLOCK, 0640) = 11 3088 fcntl(11, F_GETFD) = 0 3088 fcntl(11, F_SETFD, FD_CLOEXEC) = 0 3088 fchown(11, 0, 4294967295) = 0 3088 fchown(11, 4294967295, 0) = 0 3088 fchmod(11, 0640) = 0` We can close the thread. Thanks, Matthias ---
**Author:** ![Jens-U](https://avatars.discourse-cdn.com/v4/letter/j/d78d45/32.png) [@Jens-U](https://forums.suse.com/u/Jens-U)\ **Post date:** [March 29, 2016, 5:12pm UTC](https://forums.suse.com/t/dev-null-or-dev-urandom-with-wrong-perms-0660-after-reboot/28021/6 "2016-03-29T17:12:08Z")
Hi Matthias, [QUOTE=gurucubano;32051]As often, the problem was a mixture of two or more. […] We can close the thread.[/QUOTE] I do have weird ideas many times, but I wouldn’t have come close to that problem source 😉 Thanks for reporting back and I’ll keep that syslog side-effect in mind! Regards, Jens