Solved: Sensu won't start after upgrade to 0.23.2-2

After upgrading to Sensu 0.23.2-2 on RHEL 6.8 the Sensu server would not start. The logs looked like this:


Sensu config.json cannot be left blank

/opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-settings-3.4.0/lib/sensu/settings/loader.rb:292:in `deep_merge': undefined method `each' for nil:NilClass (NoMethodError)
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-settings-3.4.0/lib/sensu/settings/loader.rb:96:in `load_file'
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-settings-3.4.0/lib/sensu/settings.rb:17:in `load'
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-settings-3.4.0/lib/sensu/settings.rb:38:in `get'


Solved: postfix lost connection after EHLO on RHEL7

I needed to get some software from a lab that only distributes the software as .zip attachments by email. Let's ignore the wisdom of choosing that distribution method in 2016 (nowadays most mail setups strip out zipped attachments) and instead focus on the problem at hand.

I set up a local account on a RHEL7 server running Postfix. When the message was sent to me, this is what appeared in the logs:

Enabling Jumbo Frames on RHEL7 with nmcli

Use the NetworkManager command-line tool to see your connections:

# nmcli connection show --active
em1 7bb105a5-f663-4e5b-a8aa-fdeb2a16e1a0 802-3-ethernet em1

View the attributes of a single connection:

# nmcli connection show em1
802-3-ethernet.mtu: auto

Change the MTU to your new value (in this example, 9000):

# nmcli connection modify em1 802-3-ethernet.mtu 9000



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