This server is on Ubuntu 16.04, Linux 4.4.0-142-genericls
Executing ls -la /dev/null after system reboot returns:
srwxr-xr-x 1 root root 0 Feb 18 23:22 null
The correct /dev/null permissions are
crw-rw-rw- 1 root root 1, 3 Feb 18 15:01 null
The "s" means socket type file, the "x" stands for executable.
Sometimes even removing /dev/null with rm /dev/null does not work. I have to create it elsewhere and move it to /dev/null:
mknod -m 0666 /tmp/null c 1 3
mv /tmp/null /dev/null
Many services will not start for the wrong /dev/null, including apache2 and mysql.
This post about Xubuntu 15.10 is saying udev conf and MAKEDEV are the players but I still haven't found how to fix them.
