There are a few steps that need to be followed here in order to decommission a slave.

• Disable the slave in Slavealloc: https://secure.pub.build.mozilla.org/slavealloc/ui/#slaves
• Make sure it's no longer attached to a master
• Shut down the slave
• Remove it from Nagios
  • From puppet sysadmin repository (modules/nagios4/manifests/prod/releng/scl3.pp)
• Remove it from Inventory
  • DCOps must mark these machines as decommissioned
• Remove it from buildbot-configs
  • mozilla-tests/production_config.py or mozilla/production_config.py
• Finally, remove that slave from buildslaves DB

Useful bug examples

• Bug 1396454
• Bug 1402830