[Bug 2083240] Re: buildd system user lacks homedir leading to issues with snaps[and more]

[Timo Aaltonen]

Hello John, or anyone else affected,

Accepted livecd-rootfs into noble-proposed. The package will build now
and be available at https://launchpad.net/ubuntu/+source/livecd-
rootfs/24.04.81 in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
noble to verification-done-noble. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-noble. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Tags removed: verification-done verification-done-noble
** Tags added: verification-needed verification-needed-noble

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https://bugs.launchpad.net/bugs/2083240

Title:
  buildd system user lacks homedir leading to issues with snaps[and
  more]

Status in livecd-rootfs package in Ubuntu:
  Fix Released
Status in livecd-rootfs source package in Noble:
  Fix Committed
Status in livecd-rootfs source package in Oracular:
  Fix Committed
Status in livecd-rootfs source package in Plucky:
  Fix Released

Bug description:
  when running a Noble buildd image as a CI runner, the following error
  occurs

  ```
  Running job phase...
  Running test:0
  cmd_run.go:1129: WARNING: cannot create user data directory: cannot create snap home dir: mkdir /nonexistent: permission denied
  Sorry, home directories outside of /home needs configuration.
  See https://forum.snapcraft.io/t/11209 for details.
  ```

  the buildd user is created with the following code in livecd-
  rootfs/live-build/buildd/02-user.chroot

  ```
  # Create the buildd user and group.
  addgroup --gid 2501 buildd
  adduser --system --disabled-password --gecos 'Build Daemon user' \
      --ingroup buildd --uid 2001 --shell /bin/bash buildd
  mkdir -p /build/buildd
  chown buildd:buildd /build/buildd
  ```

  as of 24.04 (maybe earlier), adduser does not create a homedir for
  system users:

  > If no home directory is specified, the default home directory for a
  new system user is /nonexistent.  This directory should never exist on
  any Debian system, and adduser will never create it automatically.

  on jammy and earlier images, the following ends up the user conf

  ```
  buildd:x:2001:2501:Build Daemon user,,,:/home/buildd:/bin/bash
  ```

  and on 24.04

  ```
  buildd:x:2001:2501:Build Daemon user,,,:/nonexistent:/bin/bash
  ```

  this is fixed by adding an explicit `--home /home/buildd` to the user
  creation call

  [ Impact ]

  * Current buildd images are unable to use snaps (and likely other
  issues, since it has assumed an existing $HOME)

  * fix has no impact outside buildd, as the fix is only in a buildd
  hook

  [ Test Plan ]

  * basic testing:
      * build image locally
      * check the created buildd user does have a homedir
      * attempt to install and run a snap
  * expanded testing: 
      * NOTE: this may not be possible, depending on how launchpad is able to consume images. if not possible, do not consider blocking, and instead get sign off from the Launchpad team that the basic testing is acceptable
      * build image in launchpad using a PPA of livecd-rootfs
      * point launchpad team to build
      * consume buildd image from the launchpad build
      * execute a build in the qa environment that requires a snap

  [ Where problems could occur ]

  * if the call is incorrect, no homedir will be made and the fix will fail. 
  * it's livecd-rootfs, so layers and layers of bash. that can always go wrong. 

  [ Other Info ]

  * we'll need to expedite as this is causing issues in launchpad
  production now.

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