Show open file descriptors

Count open file descriptors for a running process

cat /proc/$(pgrep myapp)/fd | wc -l

More linux commands

Check SELinux status

getenforce

Show current SELinux enforcement mode
List cron jobs (system)

ls /etc/cron.* /var/spool/cron/crontabs/

List all system and user cron job locations
Show environment variables

printenv | sort

Display all environment variables sorted alphabetically
Watch disk I/O

iostat -xz 1

Show extended disk I/O statistics updated every second
Show process tree

pstree -p

Display process hierarchy with PIDs