Bug#867997: jessie->stretch, all apt clients break with /var/lib/dpkg/status realpath error

Alan Schwartz:
>> Sorry to hear you had issues with the upgrade.
>>
>> The problem you describe appears to be related to the release notes item
>> [5.3.2] (5.3.2.1 actually, but I cannot find the direct link to that).
>> The exact case with /var/lib/dpkg/status is not mentioned, but it could
>> be that there are some permissions on your system that forbit "_apt" to
>> access /var/lib/dpkg/status.
>>
>> * Could you please try to login in as the _apt user and check that it
>>   can read /var/lib/dpkg/status?
> 
> Due to the /nonexistent home directory and /bin/false login shell,
> it does not appear to be possible to log in as _apt:
> 
> [...]

For future reference, you can "by-pass" that by using:

 su -s/bin/bash _apt

That will grant you a shell as _apt provided it is run as root
(regardless of _apt's login shell and $HOME).

> _apt$ apt-get check
> E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission
> denied)
> E: Unable to lock the administration directory (/var/lib/dpkg/), are you
> root?
> 

FTR; I don't think that "apt-get check" is supposed to work as non-root.

>>   - If it fails, please attempt to figure out where the permission
>>     fails (e.g. [dir-test])
> 
> # ls -ld / /var /var/lib /var/lib/dpkg /var/lib/dpkg/status
> drwxr-xr-x 21 root root    1024 Jul 10 11:21 /
> drwxr-xr-x 13 root root    4096 May  7  2013 /var
> drwxr-xr-x 74 root root    4096 Jul  7 16:01 /var/lib
> drwxr-xr-x  8 root root    4096 Jul 11 08:48 /var/lib/dpkg
> -rw-r--r--  1 root root 1961225 Jul 11 08:48 /var/lib/dpkg/status
> 
> As you can see, none of these are writable by _apt; however, these are
> the same permissions I see on the other (working)

Indeed, and _apt does not need write access to the status file.

Does it work if you disable the sandbox user, e.g. by using:
  apt-get -o APT::Sandbox::User=root update

Thanks,
~Niels