fakeroot + host=ubuntu2204 + guest=ubuntu1804 => version GLIBC_nnn not found

[d-a-v]

Version of Apptainer

1.1.3+192-g3c5eb2a27

Expected behavior

Valid execution of apt update in %post section using fakeroot, ubuntu 22.04 on host, ubuntu 18.04 in def file

Actual behavior

INFO:    User not listed in /etc/subuid, trying root-mapped namespace
INFO:    The %post section will be run under fakeroot
INFO:    Starting build...
Getting image source signatures
Copying blob a404e5416296 skipped: already exists  
Copying config 9655459614 done  
Writing manifest to image destination
Storing signatures
2022/11/09 11:41:39  info unpack layer: sha256:a404e54162968593b8d92b571f3cdd673e4c9eab5d9be28d7c494595c0aa6682
INFO:    Running post scriptlet
/.singularity.d/libs/faked: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.33' not found (required by /.singularity.d/libs/faked)
/.singularity.d/libs/faked: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.34' not found (required by /.singularity.d/libs/faked)
fakeroot: error while starting the `faked' daemon.
/.singularity.d/libs/fakeroot: 1: kill: Usage: kill [-s sigspec | -signum | -sigspec] [pid | job]... or
kill -l [exitstatus]
FATAL:   While performing build: while running engine: exit status 1

Steps to reproduce this behavior

OS:

Description:    Ubuntu 22.04.1 LTS

run1804.def:

Bootstrap: docker
From: ubuntu:18.04

%post
    apt -y update

command:

apptainer build ./run1804.sif ./run1804.def

What OS/distro are you running

$ cat /etc/os-release
PRETTY_NAME="Ubuntu 22.04.1 LTS"
NAME="Ubuntu"
VERSION_ID="22.04"
VERSION="22.04.1 LTS (Jammy Jellyfish)"
VERSION_CODENAME=jammy
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=jammy

How did you install Apptainer

Apptainer is installed from source

$ apptainer version
1.1.3+192-g3c5eb2a27

Same result is obtained with the debian packages from the github release page (I tried 1.1.3, 1.1.2, 1.1.0).

HOWEVER-1

• everything is fine with HOST version as 20.04, image as 18.04
• everything is fine with HOST version as 22.04, image as 20.04
• everything is fine with HOST version as 22.04, image as 22.04

HOWEVER-2

• eveything is fine when user is referenced inside /etc/subuid and /etc/subgid

[DrDaveD]

This is a known limitation of the fakeroot-command based fake root (I think of it as "fake" fakeroot). As the fakeroot documentation says under mode 3: "the fakeroot command is bound in from the host so if the host libc library is of a very different vintage than the corresponding container library the fakeroot command can fail. If that situation happens it can be worth trying to run apptainer under the unshare -r command which is essentially the same thing as running in a root-mapped user namespace; in that case Apptainer will not try to run the fakeroot command even if it is in the user’s PATH."