[Bug 2075546] Re: Cannot install into target '/tmp/ubuntu-image-XXX/chroot' mounted with noexec or nodev

[Paul Mars]

I see 2 candidates (into which creating the ubuntu-image-XXXXXXX dir for
each build):

- the current working directory 
- /var/tmp AFAICS this is currently still under the / mountpoint, so it should be safer from size constraints and noexec/nodev permissions restrictions.


The drawback of not using /tmp anymore is that we risk filling the disk with failed build directories without the user noticing and without any chance to be saved by a reboot.

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Title:
  Cannot install into target '/tmp/ubuntu-image-XXX/chroot' mounted with
  noexec or nodev

Status in Ubuntu Image:
  New

Bug description:
  On a fresh oracular installation /tmp is a tmpfs mounted by systemd
  tmp.mount which is mounted with nodev permissions. This leads to the
  following error when trying to run ubuntu-image:

  [0] prepare_gadget_tree                                                                                                                                                                                              
  [1] load_gadget_yaml                                                                                                                                                                                                 
  [2] verify_artifact_names                                                                                                                                                                                            
  [3] germinate                                                                                                                                                                                                        
  [4] create_chroot                                                                                                                                                                                                    
  Error: Error running debootstrap command "/snap/ubuntu-image/876/usr/sbin/debootstrap --arch arm64 --variant=minbase --include=ca-certificates --components=main,universe,multiverse,restricted oracular /tmp/ubuntu-
  image-100185c6-1f8d-4d44-88e8-20fa8b330c1e/chroot http://ports.ubuntu.com/ubuntu-ports/". Error is "exit status 1". Output is: 
  /snap/ubuntu-image/876/usr/sbin/debootstrap: 1638: cannot create /tmp/ubuntu-image-100185c6-1f8d-4d44-88e8-20fa8b330c1e/chroot/test-dev-null: Permission denied
  E: Cannot install into target '/tmp/ubuntu-image-100185c6-1f8d-4d44-88e8-20fa8b330c1e/chroot' mounted with noexec or nodev

  Looking at mount this is confirmed:

  $ mount | grep /tmp
  tmpfs on /tmp type tmpfs (rw,nosuid,nodev,nr_inodes=1048576,inode64)

  The offender is the systemd tmp.mount target:

  $ systemctl cat tmp.mount
  # /usr/lib/systemd/system/tmp.mount
  #  SPDX-License-Identifier: LGPL-2.1-or-later
  #
  #  This file is part of systemd.
  #
  #  systemd is free software; you can redistribute it and/or modify it
  #  under the terms of the GNU Lesser General Public License as published by
  #  the Free Software Foundation; either version 2.1 of the License, or
  #  (at your option) any later version.

  [Unit]
  Description=Temporary Directory /tmp
  Documentation=https://systemd.io/TEMPORARY_DIRECTORIES
  Documentation=man:file-hierarchy(7)
  Documentation=https://systemd.io/API_FILE_SYSTEMS
  ConditionPathIsSymbolicLink=!/tmp
  DefaultDependencies=no
  Conflicts=umount.target
  Before=local-fs.target umount.target
  After=swap.target

  [Mount]
  What=tmpfs
  Where=/tmp
  Type=tmpfs
  Options=mode=1777,strictatime,nosuid,nodev,size=50%%,nr_inodes=1m

  Which is part of the systemd package in oracular:

  $ dpkg -S /usr/lib/systemd/system/tmp.mount
  systemd: /usr/lib/systemd/system/tmp.mount

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