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podman

podman is a work-alike alternative to docker. Perhaps the main distinction from docker is that podman stores image layers in the user’s home directory and does not have a daemon.

Finding images on registries

$ podman search --list-tags 'docker.io/scientificlinux/sl
NAME                          TAG
docker.io/scientificlinux/sl  6
docker.io/scientificlinux/sl  7
docker.io/scientificlinux/sl  latest

Running images on registries

$ podman run -ti 'docker.io/scientificlinux/sl:7'
[root@b52fd1a557be /]# yum -y install redhat-lsb-core
[root@b52fd1a557be /]# lsb_release -a
LSB Version:	:core-4.1-amd64:core-4.1-noarch
Distributor ID:	Scientific
Description:	Scientific Linux release 7.9 (Nitrogen)
Release:	7.9
Codename:	Nitrogen

Building a custom image

This images adds packages to the base SL7 as needed to pass SciSoft’s checkPrerequisites script.

$ cd docker
$ podman build -t wirecell/slscisoft slscisoft/
...
STEP 8/8: RUN bash checkPrerequisites
checkPrerequisites 1.04.01
INFO: Checking prerequisites for art and dependent packages.
INFO: All known prerequisites satisfied for art and dependencies.

$ podman run -ti wirecell/slscisoft lsb_release -a
LSB Version:	:core-4.1-amd64:core-4.1-noarch
Distributor ID:	Scientific
Description:	Scientific Linux release 7.9 (Nitrogen)
Release:	7.9
Codename:	Nitrogen

$ podman run -v /cvmfs:/cvmfs -ti wirecell/slscisoft
[root@4b0eec516074 /]# source /cvmfs/larsoft.opensciencegrid.org/setup_larsoft.sh
[root@4b0eec516074 /]# setup larsoft v09_77_00 -q c14:prof
[root@4b0eec516074 /]# art --version
art 3.12.00

User environment

A more friendly base environment which ends in a non-privileged user.

$ podman build -t wirecell/sluser sluser/ 
$ mkdir /srv/bv/sl7
$ podman run --userns=keep-id -v /srv/bv/sl7:/data -v /cvmfs:/cvmfs -ti wirecell/sluser
[user@4803d56ae213 ~]$ touch /data/junk
[user@4803d56ae213 ~]$ whoami
user
[user@4803d56ae213 ~]$ exit
$ ls -l /srv/bv/sl7/junk 
-rw-r--r-- 1 bv 100100 0 Aug  2 14:34 /srv/bv/sl7/junk

This has a problem with both --userns=keep-id and -v /cvmfs:

[user@9bd4f5726e5b ~]$ ls /cvmfs/larsoft.opensciencegrid.org/
ls: cannot access /cvmfs/larsoft.opensciencegrid.org/: Too many levels of symbolic links

Without --userns=keep-id this error message can also happen and avoided by first accessing the CVMFS path from the host prior to starting the container. But, with --userns=keep-id, nothing I find can avoid this problem. So we turn to Singularity.

Make and use singularity image

A Singularity image is smaller and more convenient for doing software development:

$ podman save --format oci-archive wirecell/sluser -o sluser.tar
$ singularity build sluser.sif oci-archive://sluser.tar

$ ls -lh sluser.*
-rwxr-xr-x 1 bv bv 357M Aug  4 10:54 sluser.sif
-rw-r--r-- 1 bv bv 600M Aug  4 10:52 sluser.tar

$ ./sluser.sif lsb_release -a
LSB Version:	:core-4.1-amd64:core-4.1-noarch
Distributor ID:	Scientific
Description:	Scientific Linux release 7.9 (Nitrogen)
Release:	7.9
Codename:	Nitrogen

$ singularity exec --bind /cvmfs sluser.sif ls /cvmfs/larsoft.opensciencegrid.org/
new_repository	packages  products  setup_larsoft.sh

$ singularity exec --bind /cvmfs sluser.sif bash
Singularity> source /cvmfs/larsoft.opensciencegrid.org/setup_larsoft.sh 
Singularity> setup larsoft v09_77_00 -q c14:prof
Singularity> art --version
art 3.12.00