[Bug 1707222] Re: usage of /tmp during boot is not safe due to systemd-tmpfiles-clean

[Scott Moser]

>From another bug with the same root cause, a failure might look like this:
Apr 12 07:56:33 ubuntu [CLOUDINIT] util.py[DEBUG]: Running command ['mount', '-o', 'ro,sync', '-t', 'auto', '/dev/sr0', '/tmp/tmpzq70nqyi'] with allowed return codes [0] (shell=False, capture=True)
Apr 12 07:56:33 ubuntu [CLOUDINIT] util.py[DEBUG]: Failed mount of '/dev/sr0' as 'auto': Unexpected error while running command.#012Command: ['mount', '-o', 'ro,sync', '-t', 'auto', '/dev/sr0', '/tmp/tmpzq70nqyi']#012Exit code: 32#012Reason: -#012Stdout: ''#012Stderr: 'mount: mount point /tmp/tmpzq70nqyi does not exist\n'
Apr 12 07:56:33 ubuntu [CLOUDINIT] util.py[DEBUG]: Recursively deleting /tmp/tmpzq70nqyi

** Changed in: cloud-init
       Status: New => Confirmed

** Changed in: cloud-init
   Importance: Undecided => Medium

** Changed in: cloud-init (Ubuntu)
   Importance: Undecided => High

** Changed in: cloud-init
   Importance: Medium => High

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/1707222

Title:
  usage of /tmp during boot is not safe due to systemd-tmpfiles-clean

Status in cloud-init:
  Confirmed
Status in cloud-init package in Ubuntu:
  Confirmed
Status in systemd package in Ubuntu:
  Won't Fix

Bug description:
  Earlier this week on Zesty on Azure I saw a cloud-init failure in its 'mount_cb' function.
  That function esentially does:
   a.) make a tmp directory for a mount point
   b.)  mount some filesystem to that mount point
   c.) call a function
   d.) unmount the directory

  What I recall was that access to a file inside the mount point failed during 'c'.
  This seems possible as systemd-tmpfiles-clean may be running at the same time as cloud-init (cloud-init.service in this example).

  
  It seems that this service basically inhibits *any* other service from using tmp files.
  It's ordering statements are only:

    After=local-fs.target time-sync.target
    Before=shutdown.target

  So while in most cases only services that run early in the boot
  process like cloud-init will be affected, any service could have its
  tmp files removed.  this service could take quite a long time to run
  if /tmp/ had been filled with lots of files in the previous boot.

To manage notifications about this bug go to:
https://bugs.launchpad.net/cloud-init/+bug/1707222/+subscriptions