Installing Perl Modules from CPAN

When there are special requirements then the need for additional Perl modules may arise. Fortunately, Perl has an excellent package repository that can satisfy almost all needs. That repository is called CPAN and is available at https://metacpan.org/.

It is recommended to use the command line client cpanm for installing modules. cpanm is often already installed on your system. Please see https://metacpan.org/pod/App::cpanminus for what to do when is isn’t already available.

Alternatively, many Perl modules are also available as packages for your operating system. These packages can be installed with your systems regular package manager.

Per default cpanm installs modules into a systemwide location. In this case modules must be installed as the root user. For example, the command

root> cpanm Acme::Dice

ergibt z. B.:

otobo> perldoc -l Acme::Dice
/usr/local/share/perl/5.30.0/Acme/Dice.pm

Docker-based installations

Special care must be taken when OTOBO runs under Docker. In this case an installation into a systemwide location would initially work as well. However, due to how Docker works, this installed modules would be lost when the container is restarted. Therefore the modules must be installed into a location that does survive a restart. The directory /opt/otobo/local within the volume otobo_opt_otobo can be used for that. Modules that are installed in /opt/otobo/local will be picked up by Perl because the environment variables PERL5LIB and PATH are preset accordingly.

The installed Perl modules will also be available after an upgrade of OTOBO. There is the general rule that files added to /opt/otobo won’t be removed by an upgrade.

For installing Perl modules in a specific location we need to modify our install command. Specicifically, we need to add the option --local-lib. Here is a sample session in the container web.

# starting a bash session in the container web
docker_admin> cd /opt/otobo-docker/
docker_admin> docker-compose exec web bash
otobo@6ef90ed00cd0:~$ pwd
/opt/otobo

# installing the sample module Acme::Dice
otobo@6ef90ed00cd0:~$ cpanm --local-lib local Acme::Dice
--> Working on Acme::Dice
Fetching http://www.cpan.org/authors/id/B/BO/BOFTX/Acme-Dice-1.01.tar.gz ... OK
Configuring Acme-Dice-1.01 ... OK
Building and testing Acme-Dice-1.01 ... OK
Successfully installed Acme-Dice-1.01
1 distribution installed

# confirm the installation directory
otobo@6ef90ed00cd0:~$ perldoc -l Acme::Dice
/opt/otobo/local/lib/perl5/Acme/Dice.pm

# locally installed module is found because the environment is preset accordingly
otobo@6ef90ed00cd0:~$ echo $PERL5LIB
/opt/otobo_install/local/lib/perl5:/opt/otobo/local/lib/perl5
otobo@6ef90ed00cd0:~$ echo $PATH
/opt/otobo_install/local/bin:/opt/otobo/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin