[Bug 1690299] Re: Cannot remove detached devices from container

[Launchpad Bug Tracker]

This bug was fixed in the package lxd - 2.15-0ubuntu5

---
lxd (2.15-0ubuntu5) artful; urgency=medium

  * Cherry-pick upstream fixes:
- 0006-lxc-config-Removal-of-multiple-devices-at-once.patch (LP: #1690299)
- 0007-network-Don-t-fail-on-non-process-PIDs.patch (LP: #1698712)
- 0008-config-Try-to-be-clever-about-in-snapshots.patch (LP: #1694855)
- 0009-Fix-readonly-mode-for-directory-mount.patch
- 0010-client-Fix-race-condition-in-operation-handling.patch
- 0011-import-keep-volatile-keys.patch
- 0012-import-remove-last-dependency-on-symlink.patch
- 0013-Better-handle-errors-in-memory-reporting.patch
- 0014-client-Don-t-live-migrate-stopped-containers.patch

 -- Stéphane Graber   Mon, 03 Jul 2017 18:19:16
-0400

** Changed in: lxd (Ubuntu)
   Status: Fix Committed => Fix Released

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Title:
  Cannot remove detached devices from container

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[Bug 1690299] Re: Cannot remove detached devices from container

[Stéphane Graber]

** Changed in: lxd (Ubuntu)
 Assignee: (unassigned) => Stéphane Graber (stgraber)

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Title:
  Cannot remove detached devices from container

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[Bug 1690299] Re: Cannot remove detached devices from container

[Stéphane Graber]

Just spent an hour attempting to implement the "optional" property and I'm 
afraid it can't be done in a sane way due to:
 - We rely on the path existing on the host at the time the device is added to 
read a number of flags from it for config validation
 - We rely on the bind-mount device existing during removal so we can 
unconfigure the cgroup limits.

I had a commit which attempted to workaround most of those, but it ended
up making "optional" such a special case that half the validation code
would be bypassed and cgroup configuration might have ended up left
behind after device removal which could be a potential security risk for
privileged containers...

So I'll only be submitting the batch removal fix for this issue.

** Changed in: lxd (Ubuntu)
   Status: Triaged => Fix Committed

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Title:
  Cannot remove detached devices from container

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[Bug 1690299] Re: Cannot remove detached devices from container

[Stéphane Graber]

stgraber@castiana:~/data/code/lxc/lxd (stgraber/master)$ lxc config device 
remove c1 test1 test2
Device test1, test2 removed from c1

So I have that part implemented now, it should make it to LXD 2.16.

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Title:
  Cannot remove detached devices from container

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[Bug 1690299] Re: Cannot remove detached devices from container

[Stéphane Graber]

The removal of multiple devices at once, I'll do as part of my new-
client branch as the new client library makes that much easier. I spent
30min trying to hook things up with the old client library, but all our
helper functions are meant to interact with a single device at once...

Adding the "optional" property isn't blocked on the port to the new
client library though, so hopefully I'll get to that over the next few
days.

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Title:
  Cannot remove detached devices from container

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[Bug 1690299] Re: Cannot remove detached devices from container

[Michal Kovarik]

Both proposals are useful.

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Title:
  Cannot remove detached devices from container

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[Bug 1690299] Re: Cannot remove detached devices from container

[Stéphane Graber]

Okay, so I figured out what's going on here and while not ideal, it
actually makes sense.

unix-char and unix-block devices don't have an "optional" property,
therefore LXD will fail to start any container which lists such a device
without the host path existing.

LXD also validates the container configuration to be valid whenever a change to 
it is done.
When removing one of the device, the client tool gives LXD an updated container 
config which includes the remaining device. That device is invalid and so LXD 
fails the config validation and returns the error.

The way around the issue is to use "lxc config edit" to remove both
devices in one shot. That way the LXD configuration will be valid.


There are a couple of things we could do to make this easier:
 - Add an "optional" flag to unix-char and unix-block, allowing you to specify 
devices which may not yet exist. The container would then start fine and the 
config would be considered valid by the validator even if those devices are 
missing. When the device shows up again, a restart would be needed to have it 
show up in the container again.

 - Allow for multiple device names to be passed to "lxc config device
remove". This would let you remove both devices in one shot, resulting
in a valid configuration.


Let me know if either/both of those would be useful to you. Until then, use 
"lxc config edit" to remove both devices.

** Changed in: lxd (Ubuntu)
   Status: New => Triaged

** Changed in: lxd (Ubuntu)
   Importance: Undecided => Medium

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Title:
  Cannot remove detached devices from container

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[Bug 1690299] Re: Cannot remove detached devices from container

[Michal Kovarik]

** Description changed:

  When multiple unix-char or unix-block devices are attached to container
  and detached from system it's not possible to remove that missing
  devices from container.
  
  Steps to reproduce:
- 1) plug two usb drive to system (in my case sda, sdb)
+ 1) plug two usb drives to system (in my case sda, sdb)
  2) create container: lxc launch ubuntu: test
  3) attach devices:
  lxc config device add test sdb unix-block path=/dev/sdb
  lxc config device add test sdc unix-block path=/dev/sdc
  4) stop the container: lxc stop test
- 5) try to start container
- 6) try to remove sdb and sdc device
+ 5) remove usb drives physically
+ 6) try to start container
+ 7) try to remove sdb and sdc device
  
  Current results:
  $ lxc start test
  error: Missing source '/dev/sdb' for device 'sdb'
  Try `lxc info --show-log test` for more info
  $ lxc config device remove test sdb
  error: The device path doesn't exist on the host and major/minor wasn't 
specified.
  $ lxc config device list test
  sdb: unix-block
  sdc: unix-block

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Title:
  Cannot remove detached devices from container

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[Bug 1690299] Re: Cannot remove detached devices from container

[Michal Kovarik]

Version - 2.12-0ubuntu1~ubuntu16.04.1

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Title:
  Cannot remove detached devices from container

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