Can't use pbuilder inside simple lxc container?

[Dan Kegel]

On Ubuntu 18.04, I was trying to reproduce a problem, so I spun up an lxc container and ran my reproduce script in it, i.e.

#!/bin/sh
set -ex
sudo apt install dh-make-golang
DIST=bionic git-pbuilder create
dh-make-golang github.com/gomatic/renderizer
cd renderizer/
gbp buildpackage --git-dist=bionic --git-pbuilder

This failed with

+ DIST=bionic git-pbuilder create
I: Invoking pbuilder
I: forking: pbuilder create --buildplace /var/cache/pbuilder/base-bionic.cow --mirror http://archive.ubuntu.com/ubuntu --distribution bionic --no-targz --extrapackages cowdancer
W: /home/ubuntu/.pbuilderrc does not exist
I: Running in no-targz mode
I: Distribution is bionic.
I: Current time: Sat Sep 8 14:40:20 UTC 2018
I: pbuilder-time-stamp: 1536417620
I: Building the build environment
I: running debootstrap
/usr/sbin/debootstrap
mknod: /var/cache/pbuilder/base-bionic.cow/test-dev-null: Operation not permitted
E: Cannot install into target '/var/cache/pbuilder/base-bionic.cow' mounted with noexec or nodev

Sad face. Not sure who's at fault here, is it me, debootstrap, pbuilder, or gbp?

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: pbuilder 0.229.1
ProcVersionSignature: User Name 4.15.0-33.36-generic 4.15.18
Uname: Linux 4.15.0-33-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
Date: Sat Sep 8 14:47:59 2018
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
SourcePackage: pbuilder
UpgradeStatus: No upgrade log present (probably fresh install)

[Dan Kegel (dank)]

Correction: the repro script was

#!/bin/sh
set -ex
sudo apt install dh-make-golang
DIST=bionic git-pbuilder create dh-make-golang github.com/gomatic/renderizer
dh-make-golang github.com/gomatic/renderizer
cd renderizer/
gbp buildpackage --git-dist=bionic --git-pbuilder

[Mattia Rizzolo (mapreri)]

That's your lxc configuration that doesn't allow mknode(2), so you can't run debootstrap within it. So it'd say your environment is too restrictive to do what you want to do.

[Dan Kegel (dank)]

Oh? Then you think https://bugs.launchpad.net/ubuntu/+source/makedev/+bug/1675163 was decided incorrectly, and makedev should indeed create devices inside lxc containers?

[Mattia Rizzolo (mapreri)]

Yes and no. In the case of the makedev installation phase I think it can be somewhat senseful to not create the device nodes if it's not going to work.

But here we are talking about debootstrap, which only creates a very few device nodes for some important devs, like /dev/null… You are going to need it, if you disallow its creation you can't expect it to work.

For this case, I expect just running the deboostrap (= `pbuilder create`) phase out of lxc and the rest inside to just work, btw.