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[SOLVED] mount root on LVM "no such file or directory"
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VinzC
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Joined: 17 Apr 2004
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PostPosted: Tue Aug 21, 2018 8:41 am    Post subject: [SOLVED] mount root on LVM "no such file or directory&q Reply with quote

Hi.

I've just finished upgrading my laptop and it went well, at least I can boot it with kernel 4.9.75. But when I boot with kernel 4.14.63-r1, I'm gratified with an error message from the initramfs such as this:
Code:
mount -t ext4 -o ro,relatime,data=ordered /dev/dm-0 /newroot
mount: mounting /dev/dm-0 on /newroot failed: No such file or directory

But
  • *all* of the logical volumes were detected (6 actually);
  • directory /newroot exists — it's from the initramfs!
  • /dev/dm-0 exists and is the root filesystem.
Now I'm stuck and I don't know what to check.

Note that
  • I have (as you guessed) my root filesystem on LVM2;
  • I generate my initramfs with genkernel initramfs --lvm;
  • after the upgrade I rejuvenated the initramfs for kernel 4.9.75 and it works fine;
  • I'm not using systemd but openrc;
  • I'm not using Grub but extlinux (don't know why it should matter but for completeness' sake);
  • the root filesystem is passed to the kernel as root=UUID=xxx and it's OK since the initramfs successfully translated that into /dev/dm-0;
  • lvm2 is not compiled with static-libs but it seems no longer seems to matter with kernel 4.9 lineage at least, so I guess...
  • I tried running the mount instruction manually in rescue mode (typed "shell" when prompted from the initramfs) and even that fails ( 8O WTF?!?)
  • I ran blkid /dev/dm-0 from safe mode and it returned the root file system's label and UUID so it looks like only the mount operation is the root cause...
A little help would be appreciated as I don't remember having ever run into this kind of trouble :( .

Thanks a whole lot in advance.
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Last edited by VinzC on Tue Aug 21, 2018 6:32 pm; edited 1 time in total
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VinzC
Watchman
Watchman


Joined: 17 Apr 2004
Posts: 5021
Location: Dark side of the mood

PostPosted: Tue Aug 21, 2018 6:30 pm    Post subject: Reply with quote

Turned out to be a missing module *facepalm*. I peeked at dmesg and I saw the following error message (approximately)
Code:
modprobe: could not load crc32c

So I compiled my kernel again and moved CRC32C into the kernel, rebooted and... voilààààà!

Under the hood: I had that module compiled as an external module. However it looks like genkernel misses that essential component (with kernel 4.14 at least) when building the initramfs. Flipping the {M} into a {*} in menuconfig did the job:
Code:
    Library routines  --->
        -*- CRC32/CRC32c functions
        {*} CRC32c (Castagnoli, et al) Cyclic Redundancy-Check  <-- that one is required to boot with an initramfs!


Case closed.
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