Platforms

• Introduction
  • Run-time Environment
  • Build Environment
• RedHat EL 9 (Current Supported Platform)
  • Required Packages
  • Install CVMFS
  • User namespace
  • Container Runtime

Introduction

ATLAS software may run on a machine installed with these OS flavors and versions with a few additional installations or configurations as described below.

Run-time Environment

These are for run-time compatibility and not full release build environments which may require development software.

ATLAS supports RedHat Enterprise Linux and its derived flavors (e.g. RockyLinux and AlmaLinux) for both x86_64 and aarch64 architectures. Users of other OS versions and Linux/non-Linux flavors, or who do not have root privileges, should consider running on supported default containers; e.g.

• setupATLAS -c centos6 for a centos6 container compatible with slc6
• setupATLAS -c centos7 for a centos7 container
• setupATLAS -c el9 for an el9 container.

Build Environment

If you are looking for a build environment, the recommendation is to use containers. More information is available from the Containers in the Nightly System documentation where the Dockerfiles are referenced and also instructions on how to build your own containers.

RedHat EL 9 (Current Supported Platform)

This includes derived flavors such as AlmaLinux and RockyLinux as per CERN Recommendations.

Required Packages

Enable the CRB Repo:

dnf config-manager --set-enabled crb

Install the HEP_OSlibs metarpm:

yum install https://linuxsoft.cern.ch/wlcg/el9/`uname -m`/wlcg-repo-1.0.0-1.el9.noarch.rpm

Install Kerberos:

yum install krb5-workstation

Configure Kerberos; for example a minimal configuration in /etc/krb5.conf should have:

[libdefaults]
  default_realm = CERN.CH
  ticket_lifetime = 24h
  renew_lifetime = 7d
  forwardable = true
  proxiable = true

[realms]
  CERN.CH = {
    default_domain = cern.ch
    kpasswd_server = afskrb5m.cern.ch
    admin_server = afskrb5m.cern.ch
    kdc = cerndc.cern.ch
  }

[domain_realm]
  cern.ch = CERN.CH
  .cern.ch = CERN.CH

Install CVMFS

Installation of CVMFS is strongly recommended and requires root privileges.

However if that is not possible (e.g. no root privileges), atlas-cvmfsexec can be used.

User namespace

By default user namespace is enabled on EL9. This can be verified by:

sysctl user.max_user_namespaces

If the resulting user.max_user_namespaces is set to 0, that means that user namespace is disabled and Apptainer container runtimes from CVMFS will not work. There are 2 solutions to this which require root privileges:

• Either (and highly recommend) that user namespace be enabled on the machine.

  echo "user.max_user_namespaces = 30561"  > /etc/sysctl.d/90-max_user_namespaces.conf
  sysctl -p /etc/sysctl.d/90-max_user_namespaces.conf
  

• Or install a local version of Apptainer with suid.

Container Runtime

By default, Apptainer from CVMFS will be used if user namespace is enabled. However other runtimes such as Docker, Podman, Shifter and Singularity are also supported. Nested containers (running a container within a container) is only possible with Apptainer from CVMFS which in turn requires user namespace be enabled.