On 03/05/15 21:26, Leslie Rhorer wrote:
I am having a persistent problem. I have an array system that is having problems. Obviously, that needs to get fixed, but it is taking quite some time to find the root cause. In the meantime, the array is not bootable, so it is not needed during the initrd phase of the startup. Previously, this made little difference, but in Jessie, the system refuses to transition to Runlevel 2 while any mount target in fstab is failing. This is a real problem, because the system is headless, and getting the system working from the console is a huge pain. I don't think this behavior was present prior to Jessie. In any case, does anyone have any recommendations on how to get the system to boot at least to the point where ssh is available even if the array assembly fails?
By default, all entries in /etc/fstab are "auto" (mount automatically at boot) and "fail" (treat failure to mount as an error condition).
sysvinit mounts those filesystems by invoking "mount -a", and doesn't actually pay any attention to the exit status of that command. Even if half the world doesn't get mounted, sysvinit will stumble on with its attempt to bring up the system.
systemd, on the other hand, treats "auto,fail" filesystems as being Required (i.e. a hard dependency) by "local-fs.target", which is a dependency of the various "normal operation" targets analogous to sysvinit runlevels 2-5. Any mount failure among those filesystems will result in systemd refusing to complete the boot sequence, as something important is clearly missing.
There are two ways to resolve this by editing /etc/fstab:1. Mark the affected filesystems 'noauto' while they are out of commission; this prevents them from being automatically mounted.
2. Mark the affected filesystems 'nofail' while they are out of commission; this reduces the dependency from "Requires" (hard dependency) to "Wants" (soft dependency i.e. systemd will try to mount them, but will not treat a failure to do so as preventing the boot sequence from completing).