Install singularity: PASSED

[centos@singularity-3 ~]$ hostname
singularity-3.8.1-centos-7-epel-testing.novalocal
[centos@singularity-3 ~]$ cat /etc/os-release 
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"

[centos@singularity-3 ~]$ sudo yum -y install singularity-3.8.1 --enablerepo=epel-testing
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
 * base: ftpmirror.your.org
 * epel: mirror.math.princeton.edu
 * epel-testing: mirror.math.princeton.edu
 * extras: mirror.netdepot.com
 * updates: repo1.dal.innoscale.net
Resolving Dependencies
--> Running transaction check
---> Package singularity.x86_64 0:3.8.0-1.el7 will be updated
---> Package singularity.x86_64 0:3.8.1-1.el7 will be an update
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package            Arch          Version             Repository           Size
================================================================================
Updating:
 singularity        x86_64        3.8.1-1.el7         epel-testing         37 M

Transaction Summary
================================================================================
Upgrade  1 Package

Total download size: 37 M
Downloading packages:
epel-testing/x86_64/prestodelta                            |   75 B   00:03     
singularity-3.8.1-1.el7.x86_64.rpm                         |  37 MB   00:04     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Updating   : singularity-3.8.1-1.el7.x86_64                                                                                                                    1/2 
  Cleanup    : singularity-3.8.0-1.el7.x86_64                                                                                                                    2/2 
  Verifying  : singularity-3.8.1-1.el7.x86_64                                                                                                                    1/2 
  Verifying  : singularity-3.8.0-1.el7.x86_64                                                                                                                    2/2 

Updated:
  singularity.x86_64 0:3.8.1-1.el7                                                                                                                                   

Complete!
[centos@singularity-3 ~]$ singularity --version
singularity version 3.8.1-1.el7
[centos@singularity-3 ~]$

Build (debootstrap) and exec a container from a definition file: PASSED

[centos@singularity-3 ~]$ hostname
singularity-3.8.1-centos-7-epel-testing.novalocal
[centos@singularity-3 ~]$ singularity --version
singularity version 3.8.1-1.el7
[centos@singularity-3 ~]$ sudo singularity build ubuntu-18.04.sif naked-singularity/definition-files/ubuntu/Singularity.ubuntu-18.04
INFO:    Starting build...
...
The following packages will be REMOVED:
  libdumbnet1*
0 upgraded, 0 newly installed, 1 to remove and 5 not upgraded.
After this operation, 91.1 kB disk space will be freed.
(Reading database ... 50661 files and directories currently installed.)
Removing libdumbnet1:amd64 (1.12-7build1) ...
Processing triggers for libc-bin (2.27-3ubuntu1.4) ...
INFO:    Adding labels
INFO:    Adding environment to container
INFO:    Adding runscript
INFO:    Creating SIF file...
INFO:    Build complete: ubuntu-18.04.sif
[centos@singularity-3 ~]$ singularity exec ubuntu-18.04.sif python3 --version
Python 3.6.9
[centos@singularity-3 ~]$

Pull and run a container from DockerHub: PASSED

[centos@singularity-3 ~]$ hostname
singularity-3.8.1-centos-7-epel-testing.novalocal
[centos@singularity-3 ~]$ singularity --version
singularity version 3.8.1-1.el7
[centos@singularity-3 ~]$ singularity pull docker://godlovedc/lolcow
INFO:    Converting OCI blobs to SIF format
INFO:    Starting build...
Getting image source signatures
Copying blob 9fb6c798fa41 done  
Copying blob 3b61febd4aef done  
Copying blob 9d99b9777eb0 done
...
2021/08/19 16:36:47  info unpack layer: sha256:3b61febd4aefe982e0cb9c696d415137384d1a01052b50a85aae46439e15e49a
2021/08/19 16:36:47  info unpack layer: sha256:9d99b9777eb02b8943c0e72d7a7baec5c782f8fd976825c9d3fb48b3101aacc2
2021/08/19 16:36:47  info unpack layer: sha256:d010c8cf75d7eb5d2504d5ffa0d19696e8d745a457dd8d28ec6dd41d3763617e
2021/08/19 16:36:47  info unpack layer: sha256:7fac07fb303e0589b9c23e6f49d5dc1ff9d6f3c8c88cabe768b430bdb47f03a9
2021/08/19 16:36:47  info unpack layer: sha256:8e860504ff1ee5dc7953672d128ce1e4aa4d8e3716eb39fe710b849c64b20945
INFO:    Creating SIF file...
[centos@singularity-3 ~]$ singularity run lolcow_latest.sif 
 _________________________________________
< Q: How do you keep a moron in suspense? >
 -----------------------------------------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
[centos@singularity-3 ~]$

Pull a container from GHCR via oras and shell into it: PASSED

[centos@singularity-3 ~]$ singularity pull oras://ghcr.io/mkandes/naked-singularity:ubuntu-20.04
INFO:    Downloading oras image
[centos@singularity-3 ~]$ singularity shell naked-singularity_ubuntu-20.04.sif 
Singularity> python3 --version
Python 3.8.10
Singularity> md5sum naked-singularity_ubuntu-20.04.sif 
da4e0bd4266ebdbaa68235ef74883c23  naked-singularity_ubuntu-20.04.sif
Singularity> sha256sum naked-singularity_ubuntu-20.04.sif 
4ba73520c64bdf856d25b92e0bd8a22b52f346c258a4ac101f36bead971682a2  naked-singularity_ubuntu-20.04.sif
Singularity>

Convert a SIF to a sandbox and then modify it: PASSED

[centos@singularity-3 ~]$ hostname
singularity-3.8.1-centos-7-epel-testing.novalocal
[centos@singularity-3 ~]$ singularity --version
singularity version 3.8.1-1.el7
[centos@singularity-3 ~]$ sudo singularity build --sandbox ubuntu-18.04 ubuntu-18.04.sif 
INFO:    Starting build...
INFO:    Verifying bootstrap image ubuntu-18.04.sif
WARNING: integrity: signature not found for object group 1
WARNING: Bootstrap image could not be verified, but build will continue.
INFO:    Creating sandbox directory...
INFO:    Build complete: ubuntu-18.04
[centos@singularity-3 ~]$ sudo singularity shell --writable ubuntu-18.04
Singularity> python --version
bash: python: command not found
Singularity> apt-get install python
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  libpython-stdlib libpython2.7-minimal libpython2.7-stdlib python-minimal python2.7 python2.7-minimal
Suggested packages:
  python-doc python-tk python2.7-doc binfmt-support
The following NEW packages will be installed:
  libpython-stdlib libpython2.7-minimal libpython2.7-stdlib python python-minimal python2.7 python2.7-minimal
0 upgraded, 7 newly installed, 0 to remove and 5 not upgraded.
Need to get 3967 kB of archives.
After this operation, 16.8 MB of additional disk space will be used.
Do you want to continue? [Y/n] Y
...
Setting up python2.7 (2.7.17-1~18.04ubuntu1.6) ...
Setting up libpython-stdlib:amd64 (2.7.15~rc1-1) ...
Setting up python (2.7.15~rc1-1) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for mime-support (3.60ubuntu1) ...
Singularity> python --version
Python 2.7.17
Singularity> exit
exit
[centos@singularity-3 ~]$ singularity exec ubuntu-18.04 python --version
Python 2.7.17
[centos@singularity-3 ~]$