When run as a user that belongs to a group with spaces in the name (a la Windows / Samba), Logstash fails to start. I have fixed this locally by amending line: 61
Before (not working due to names):
SGROUPS=$(id -Gn "$LS_USER" | tr " " "," | sed 's/,$//'; echo '')
After (Use GIDs):
SGROUPS=$(id -G "$LS_USER" | tr " " "," | sed 's/,$//'; echo '')
I was unable to find this in your repos otherwise I would've opened a PR...