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Sometimes /dev/disk/by-* are not filled at boot [solved]
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mv
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PostPosted: Tue Jun 10, 2014 7:41 pm    Post subject: Sometimes /dev/disk/by-* are not filled at boot [solved] Reply with quote

As the subject says:
Sometimes (meaning perhaps 1 out of 20 boots, on another machine more often) the /dev/disk/by-* devices are not filled with the /dev/sd* devices.

I would guess that for some reason udev does not do its job, since the /dev/sd* devices are available.

The logs show nothing suspicious (but the function filling /dev/disk/by-* always seems to be silent, anyway). (Of course, in the failure case hell breaks loose, once mounting is attempted, since I use LABEL= throughout my /etc/fstab).

The problem occurs roughly since a recent upgrade to hardened-sources-3.15.5*, but I cannot say precisely, since the problem is not reproducible enough; I think once it also failed with some hardened-sources-3.15.4*, too.

I am using systemd-213.

For some strange reason, not passing the kernel option "quiet" seems to suppress the problem. But not always...


Last edited by mv on Tue Jun 24, 2014 7:26 pm; edited 1 time in total
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ulenrich
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PostPosted: Tue Jun 10, 2014 8:27 pm    Post subject: Reply with quote

Hi mv,
I saw this misbehavior using a not hardened plain vanilla linux-3.14.5 kernel.
It was gone during some of the following stable-queue patches on the way to linux-3.14.6

Different behavior when being verbose may hint you to a timing issue of the kernel ...
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mv
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PostPosted: Wed Jun 11, 2014 8:31 am    Post subject: Reply with quote

Thanks. So I am waiting with further analysis until some >=hardened-sources-3.14.6 appears which perhaps solves the problem...
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eccerr0r
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PostPosted: Sat Jun 14, 2014 12:07 am    Post subject: Reply with quote

I'll have to agree that there's a race condition here. I wonder if there's a kernel "rootdelay" option like what they do for initramfs to wait for the kernel and udev/mdev to get all USB devices setup ...

So do the /dev/disk/by-* eventually show up, just not ready by when fstab is read and automounted? Or are they completely MIA for that session?
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mv
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PostPosted: Sat Jun 14, 2014 5:46 pm    Post subject: Reply with quote

Quote:
I'll have to agree that there's a race condition here.

Anything non-reproducible must very likely be related with parallel or ordering issues (if hardware defect can be excluded). However, race is a special case of these issues - so far, there is no hint why it should exactly be race; it could also be an unusual ordering of initializations.
eccerr0r wrote:
So do the /dev/disk/by-* eventually show up

No, in the error case they never appear.

hardened-sources-3.14.6 is out. So far, no problem, but unfortunately this means nothing, yet: I also thought first that the problem is gone with 3.14.5-r2...
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mv
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PostPosted: Tue Jun 24, 2014 7:28 pm    Post subject: Reply with quote

Since there are still no problems with hardened-3.14.6, I think chances are good that the issue was actually solved with vanilla-3.14.6. Marking the thread as [solved].
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