## systemd/systemctl information

* units (service files) are stored in different locations depending on system/user mode
  there are several (hand chosen) types that specific symantics and cannot be renamed:
  
  basic.target = basic bootups
  crtl-alt-del.target = target started upon key combination
  default.target = starts at bootup; usually aliased to multiuser/graphical targets
  network-online.target = units which require network access need this target
  runlevel{2,3,4,5}.target = sysv5 compatible targets for respective runlevels; symlink to appropriate multi-user/graphic.target
  

* /etc/systemd/(system|user), /run/systemd/(system|user), /usr/lib/systemd/(system|user)
* user configuration always takes precedence
* must run systemctl daemon-reload after changing unit-files

* rc.d "path" = /etc/systemd/system/multi-user.target.wants/

* /var/lib/systemd/coredump	= location for coredumps 

coredumpctl list	; list core dumps
coredumpctl info PID	; get information about core dump with matching PID
coredumpctl debug PID	; start debugging session on core dump with matching PID


systemctl list-units ; displays loaded unit status
systemctl list-units --all ; display loaded but inactive units
systemctl list-unit-files ; displays all installed unit files

systemctl start 'service' ; start systemd 'service' (unit command)
systemctl start /path/to/service ; start systemd 'service' (unit file)


systemctl enable|disable 'service' ; enable/disable service (creates/removes symlinks from /usr/lib/systemd/system/)
systemctl is-enabled 'service'; boolean service check
systemctl is-active 'service'; boolean service status

systemctl show 'service' ; get full service details
systemctl list-dependencies 'service'; get tree-formated dependency list

journalctl --facility=		; filter messages by facility (local0, etc.)
				  use --facility=help to get list of known facilities
journalctl -p {0..7}		; filter messages by syslog (3) levels
journalctl -t identifier	; filter by SYSLOG_IDENTIFIER
				  use -F SYSLOG_IDENTIFIER to get list of known identifiers