[Bug 1227520] Re: Timezone changes are not working due to ro /etc and bind mounts

[Iain Lane]

If you issue timedated's SetTimezone D-Bus call and strace the daemon,
you see that it fails because of this:

  symlink("../usr/share/zoneinfo/Europe/Berlin",
"/etc/.localtime4e49606a750b8c2c") = -1 EROFS (Read-only file system)

Which means that timedated is trying, entirely sensibly, to atomically
overwrite the /etc/localtime symlink with the new timezone. This doesn't
work with our ro-/etc scheme that we have on our device images. There
will be a similar problem with updating /etc/timezone atomically too,
but that's a file instead of a symlink.

The rough workaround that we have in mind (suggested by cjwatson,
thanks) is to create a writable directory and make /etc/localtime
/etc/timezone /etc/adjtime be symlinks to files/symlinks as appropriate
inside there, which are themselves atomically updated. Do this for the
fallback case (EROFS) only.

It does mean that we'll need to play whack-a-mole with anything else
which thinks it can update these, sadly. I wonder if it'd be better to
revisit making the whole of /etc writable on our images and deal with
the conffile issues another way.

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https://bugs.launchpad.net/bugs/1227520

Title:
  Timezone changes are not working due to ro /etc and bind mounts

Status in “systemd” package in Ubuntu:
  Confirmed
Status in “ubuntu-system-settings” package in Ubuntu:
  Confirmed

Bug description:
  There is no way to set up a different timezone than automatic in the
  System Settings

  ProblemType: Bug
  DistroRelease: Ubuntu 13.10
  Package: ubuntu-system-settings 0.1+13.10.20130910.3-0ubuntu1
  Uname: Linux 3.4.0-3-mako armv7l
  ApportVersion: 2.12.2-0ubuntu1
  Architecture: armhf
  Date: Thu Sep 19 08:41:07 2013
  InstallationDate: Installed on 2013-09-18 (0 days ago)
  InstallationMedia: Ubuntu Saucy Salamander (development branch) - armhf (20130918)
  MarkForUpload: True
  ProcEnviron:
   TERM=linux
   PATH=(custom, no user)
  SourcePackage: ubuntu-system-settings
  UpgradeStatus: No upgrade log present (probably fresh install)

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