При обновлении опирался на официальную документацию. На шаге 4 возникла ошибка:

BEGIN failed--compilation aborted at /opt/otrs/Kernel/System/DateTime.pm line 27.
Compilation failed in require at /opt/otrs/Kernel/Language.pm line 20.
BEGIN failed--compilation aborted at /opt/otrs/Kernel/Language.pm line 20.
Compilation failed in require at /opt/otrs/Kernel/Output/HTML/Layout.pm line 18.
BEGIN failed--compilation aborted at /opt/otrs/Kernel/Output/HTML/Layout.pm line 18.
Compilation failed in require at /opt/otrs/Kernel/System/ObjectManager.pm line 25.
BEGIN failed--compilation aborted at /opt/otrs/Kernel/System/ObjectManager.pm line 25.
Compilation failed in require at scripts/DBUpdate-to-6.pl line 29.
BEGIN failed--compilation aborted at scripts/DBUpdate-to-6.pl line 29.

Для того чтобы залогиниться под OTRS используйте:

su -l -s /bin/bash otrs

Для исправления ошибки мне помогло:

apt-get install libdatetime-perl