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Add "dm-snapshot" to kernelModules? #33646

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jluttine opened this issue Jan 9, 2018 · 5 comments · Fixed by #62969
Closed

Add "dm-snapshot" to kernelModules? #33646

jluttine opened this issue Jan 9, 2018 · 5 comments · Fixed by #62969

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@jluttine
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jluttine commented Jan 9, 2018

Issue description

After creating an LVM snapshot, system doesn't boot.

Steps to reproduce

I took an LVM snapshot when running my system:

modprobe dm-snapshot
lvcreate -l100%FREE -s -n lv-nixos-snapshot /dev/vg-nixos/lv-nixos

Rebooted my system at some point later and got stuck in the boot with error something like: snapshot target support missing from kernel. I suppose it's because modprobe dm-snapshot isn't run. How can I make my system load that automatically?

This is probably related: https://bugzilla.redhat.com/show_bug.cgi?id=1287940

Technical details

Please run nix-shell -p nix-info --run "nix-info -m" and paste the
results.
@jluttine
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jluttine commented Jan 9, 2018 •
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I managed to boot my system by booting into a live USB OS, and then removing the snapshot lvremove /dev/vg-nixos/lv-nixos-snapshot and booting normally after that. But obviously I'd like the boot to work even if there are snapshots present.

@bjornfor
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bjornfor commented Jan 9, 2018 •
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Perhaps boot.initrd.kernelModules = [ "dm-snapshot" ]? (UPDATE: Yes, that's it.)

@bjornfor
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bjornfor commented Feb 8, 2018

Perhaps nixos-generate-config could detect LVM and add this setting automatically?

@jluttine
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I can confirm that adding boot.initrd.kernelModules = [ "dm-snapshot" ] solved the issue. I also tried boot.kernelModules = [ "dm-snapshot" ] and boot.initrd.availableKernelModules = [ "dm-snapshot" ] but they didn't help. I would like to see this option added by default (when LVM detected?) so users wouldn't so easily make their systems unbootable.

@jluttine jluttine changed the title System unbootable if LVM snapshots present Add "dm-snapshot" to kernelModules? Feb 20, 2018
@bjornfor
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Step 1, LVM detection. Here is an idea: test $(lsblk -n -o TYPE $(findmnt -n -o SOURCE /)) = lvm && echo "is lvm". (Is there a better way?)

Step 2. update nixos-generate-config.

@bjornfor bjornfor mentioned this issue Jun 10, 2019
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bjornfor added a commit to bjornfor/nixpkgs that referenced this issue Jun 16, 2019
@bjornfor
nixos-generate-config: add dm-snapshot module if LVM is detected
1b9dea5 
Without this, the system becomes unbootable if the user creates a LVM
snapshot and reboots.

Fixes NixOS#33646

(The same kind of problem was fixed in RHEL a few years back:
https://bugzilla.redhat.com/show_bug.cgi?id=1287940)
bjornfor added a commit that referenced this issue Jun 16, 2019
@bjornfor
nixos-generate-config: add dm-snapshot module if LVM is detected
4213e48 
Without this, the system becomes unbootable if the user creates a LVM
snapshot and reboots.

Fixes #33646

(The same kind of problem was fixed in RHEL a few years back:
https://bugzilla.redhat.com/show_bug.cgi?id=1287940)
bjornfor added a commit that referenced this issue Jun 16, 2019
@bjornfor
nixos-generate-config: add dm-snapshot module if LVM is detected
4f65275 
Without this, the system becomes unbootable if the user creates a LVM
snapshot and reboots.

Fixes #33646

(The same kind of problem was fixed in RHEL a few years back:
https://bugzilla.redhat.com/show_bug.cgi?id=1287940)

(cherry picked from commit 4213e48)
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nixos-generate-config: add dm-snapshot module if LVM is detected bjornfor/nixpkgs
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@bjornfor @jluttine