A little more info. The debian installed karaf starts in /var/lib/karaf/ which looks like this: sb@lorenzo:/var/lib/karaf$ ls -al total 36 drwxr-xr-x 7 karaf karaf 4096 Apr 3 17:25 . drwxr-xr-x 77 root root 4096 Nov 15 15:36 .. drwxr-xr-x 2 karaf karaf 4096 Aug 25 2017 .karaf drwxr-xr-x 3 karaf karaf 4096 Aug 25 2017 .m2 lrwxrwxrwx 1 karaf karaf 20 Apr 19 2016 bin -> /usr/share/karaf/bin drwxr-xr-x 8 karaf karaf 4096 Apr 3 17:25 data drwxr-xr-x 2 karaf karaf 4096 Apr 3 17:25 deploy -rw-r--r-- 1 karaf karaf 1846 Sep 24 2020 derby.log drwxr-xr-x 2 karaf karaf 4096 Apr 3 17:25 instances -rw-r--r-- 1 karaf karaf 5 Apr 3 17:25 karaf.pid lrwxrwxrwx 1 karaf karaf 20 Apr 19 2016 lib -> /usr/share/karaf/lib -rw-r--r-- 1 karaf karaf 0 Apr 3 17:25 lock lrwxrwxrwx 1 karaf karaf 23 Apr 19 2016 system -> /usr/share/karaf/system sb@lorenzo:/var/lib/karaf$
After uninstalling the debian package, the directory looks like this: sb@lorenzo:/var/lib/karaf$ ls -al total 24 drwxr-xr-x 5 karaf karaf 4096 Apr 5 16:50 . drwxr-xr-x 77 root root 4096 Nov 15 15:36 .. drwxr-xr-x 2 karaf karaf 4096 Aug 25 2017 .karaf drwxr-xr-x 3 karaf karaf 4096 Aug 25 2017 .m2 drwxr-xr-x 7 karaf karaf 4096 Apr 5 16:50 data -rw-r--r-- 1 karaf karaf 1846 Sep 24 2020 derby.log sb@lorenzo:/var/lib/karaf$ The /etc/karaf/ directory (which is symlinked to from /var/lib/karaf/etc/ in an installed debian package) is also left in place, so that karaf config will survive across debian versions. The /var/lib/karaf/data/ directory is deleted when uninstalling and upgrading packages, because otherwise the resulting reinstall most probably wouldn't work. (The downside of deleting the data directory, is that I need to reinstall all of my apps after doing an "apt full-upgrade" that pulls in a new version. But I can live with that)
