If the server is Linux-based, strace is great for figuring out
what’s going on with a “stuck” process.
$ strace -e file rake assets:precompile
... runs `rake assets:precompile`, printing out any time a file is
opened or checked
$ strace -e file,network,process rake assets:precompile
... the same as above, but also printing network process and subcommands run
$ strace -e file,process -f rake assets:precompile
... the -f parameter follows forks -- in case it's not `rake` but a
subshell that you're interested in
$ strace -p 1234
... connect to pid 1234 and start tracing