For /tmp
in /etc/fstab
, I have mode=1777
, but after a reboot, the permissions on /tmp
are 0755
. Another directory /var/tmp
is configured in exactly the same way but does not have this problem (see below). This is a Raspberry Pi running Ubuntu 18.04 Server. The root filesystem is a microSD card mounted read-only.
What is the proper way to make the 1777
permissions permanent?
Here are some additional details (after a fresh boot):
$ touch /tmp/test
touch: cannot touch '/tmp/test': Permission denied
$ whoami
ubuntu
$ ls -ld /tmp /var/tmp
drwxr-xr-x 9 root root 180 Dec 26 13:54 /tmp
drwxrwxrwt 4 root root 80 Dec 26 13:54 /var/tmp
$ mount |grep /tmp
tmpfs on /var/tmp type tmpfs (rw,nosuid,nodev,noexec,noatime,size=65536k)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noexec,noatime,size=131072k)
$ grep /tmp /etc/fstab
tmpfs /var/tmp tmpfs defaults,noatime,nosuid,nodev,noexec,mode=1777,size=64M 0 0
tmpfs /tmp tmpfs defaults,noatime,nosuid,nodev,noexec,mode=1777,size=128M 0 0
$ sudo systemctl status tmp.mount
● tmp.mount - /tmp
Loaded: loaded (/etc/fstab; generated)
Active: active (mounted) since Sun 2018-01-28 15:58:18 UTC; 10 months 27 days ago
Where: /tmp
What: tmpfs
Docs: man:fstab(5)
man:systemd-fstab-generator(8)
Process: 642 ExecMount=/bin/mount tmpfs /tmp -t tmpfs -o defaults,noatime,nosuid,nodev,noexec,mode=1777,size=128M (code=exited, status=0/SUCCESS)
Tasks: 0 (limit: 2146)
CGroup: /system.slice/tmp.mount
Jan 28 15:58:18 testsystem systemd[1]: Mounting /tmp...
Jan 28 15:58:18 testsystem systemd[1]: Mounted /tmp.
$ grep -R '/tmp' /etc/tmpfiles.d /usr/lib/tmpfiles.d
/usr/lib/tmpfiles.d/x11.conf:D! /tmp/.X11-unix 1777 root root 10d
/usr/lib/tmpfiles.d/x11.conf:D! /tmp/.ICE-unix 1777 root root 10d
/usr/lib/tmpfiles.d/x11.conf:D! /tmp/.XIM-unix 1777 root root 10d
/usr/lib/tmpfiles.d/x11.conf:D! /tmp/.font-unix 1777 root root 10d
/usr/lib/tmpfiles.d/x11.conf:D! /tmp/.Test-unix 1777 root root 10d
/usr/lib/tmpfiles.d/x11.conf:r! /tmp/.X[0-9]*-lock
/usr/lib/tmpfiles.d/tmp.conf:D /tmp 1777 root root -
/usr/lib/tmpfiles.d/tmp.conf:#q /var/tmp 1777 root root 30d
/usr/lib/tmpfiles.d/tmp.conf:x /tmp/systemd-private-%b-*
/usr/lib/tmpfiles.d/tmp.conf:X /tmp/systemd-private-%b-*/tmp
/usr/lib/tmpfiles.d/tmp.conf:x /var/tmp/systemd-private-%b-*
/usr/lib/tmpfiles.d/tmp.conf:X /var/tmp/systemd-private-%b-*/tmp
/usr/lib/tmpfiles.d/tmp.conf:R! /tmp/systemd-private-*
/usr/lib/tmpfiles.d/tmp.conf:R! /var/tmp/systemd-private-*
$ sudo chmod 1777 /tmp
$ ls -ld /tmp /var/tmp
drwxrwxrwt 9 root root 180 Dec 26 13:55 /tmp
drwxrwxrwt 4 root root 80 Dec 26 13:55 /var/tmp
$ cat /etc/rc.local
#!/bin/bash
service ntp start
exit 0
$ uname -a
Linux testsystem 4.15.0-1030-raspi2 #32-Ubuntu SMP PREEMPT Fri Dec 7 09:15:28 UTC 2018 armv7l armv7l armv7l GNU/Linux
Related, unanswered questions:
Best Answer
This was part of my initial configuration (because
/
is mounted read-only):Apparently at boot, the system does
chmod 755 /var/spool
, which changed/tmp
in my case.The fix was to replace the symlink with a normal directory and add a third
tmpfs
mount:Thanks to everyone for the comments which directed me in the correct direction, especially Filipe Brandenburger's "Do you have any other scripts or units messing with /tmp on startup?"