Logstash can't read files it should have access too

It turned out to be related to this bug in upstart:

https://bugs.launchpad.net/upstart/+bug/812870

Because adm was a secondary group it was not being applied to the process, which is broken as f**k and is apparently fixed in a later version.

My solution was to add setguid adm to the init file.

Here is a working workaround:

sudo vi /etc/init.d/logstash

modify

    LS_GROUP=logstash

    LS_GROUP=adm

then

sudo /etc/init.d/logstash start

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