I've successfully built a snap that I can install on my system.
However, it crashes upon start, and I'm not quite sure where to start debugging that crash.
What are the different approaches to debugging an installed app failing to start?
For debugging confined snaps (ie, installed without
--devmode) there is a snap in the store called
snappy-debug that will get better over time but is already useful. To use:
sudo snap install snappy-debug --devmode # after snapd 2.0.7 lands, drop --devmode sudo snap connect snappy-debug:log-observe ubuntu-core:log-observe sudo /snap/bin/snappy-debug.security scanlog
This scanlog command will tail the syslog, resolving seccomp syscall numbers and make suggestions on what interfaces to use, changes to make to your snap to work within the sandbox, etc. You can filter by snap with:
sudo /snap/bin/snappy-debug.security scanlog <snapname>
Some more tips are covered here:
snap try can be helpful too.