Comment 68 for bug 1522675

I am using Lubuntu 17.04, and when using Synaptic, I get the "...unsandboxed..." message after a completed download. One message per download. (Why only one? The package I just downloaded for testing purposes pulled in six or eight other packages, but only the last was shown in the message.)

The message occurs in an error window: a large triangle with an exclamation markis shown, with the large text "An error occurred", then (smaller) "The following details are provided:"
So to the user, it does not LOOK like a one-line minor warning...
Synaptic does not refresh the package listing until after dismissing the window.

I now provide 3 examples of the detail provided:

W: Download is performed unsandboxed as root as file '/var/cache/apt/archives/partial/libreoffice-style-galaxy_1%3a5.3.1-0ubuntu2_all.deb' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)

W: Download is performed unsandboxed as root as file '/var/cache/apt/archives/partial/gstreamer1.0-pulseaudio_1.10.4-1ubuntu1_amd64.deb' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)

W: Download is performed unsandboxed as root as file '/var/cache/apt/archives/partial/speedtest-cli_1.0.0-1_all.deb' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)

/var/cache/apt/archives/partial and
/var/lib/update-notifier/package-data-downloads/partial
both have Owner (Create and delete files) and Group (Access files) owned by Root.

/etc/passwd contains a line:
_apt:x:105:65534::/nonexistent:/bin/false
...so the user does exist, but is not assigned to the two directories

comment #43 says that apparently I should do a:
sudo chown _apt <...each of the two above directories...>

Should I?

How/when are these directories created in the first place?

Surely whatever created them should have set them up with _apt as owner...?

I don't think I have received this message from update-notifier, but am not sure...

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scott@scott-ASUS-M2N68-AMPLUS:~$ uname -a
Linux scott-ASUS-M2N68-AMPLUS 4.10.0-21-generic #23-Ubuntu SMP Fri Apr 28 16:14:22 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
scott@scott-ASUS-M2N68-AMPLUS:~$ lsb_release -dsc
Ubuntu 17.04
zesty
scott@scott-ASUS-M2N68-AMPLUS:~$ echo $DESKTOP_SESSION
Lubuntu

scott@scott-ASUS-M2N68-AMPLUS:~$ apt --version
apt 1.4 (amd64)

Synaptic version 0.84.2
update-notifier version 3.179