[journalctl] how to use journalctl (journalctl 사용법)

journalctl 사용법

how to use journalctl 

view basic log

$ journalctl
 7월 29 16:25:57 VirtualBox systemd-journald[214]: Runtime journal (/run/log/journal/) is 8.0M, max 80.9M, 72.9M free.
 7월 29 16:25:57 VirtualBox kernel: Initializing cgroup subsys cpuset
 7월 29 16:25:57 VirtualBox kernel: Initializing cgroup subsys cpu
 7월 29 16:25:57 VirtualBox kernel: Initializing cgroup subsys cpuacct
 7월 29 16:25:57 VirtualBox kernel: Linux version 4.4.0-116-generic (buildd@lgw01-amd64-023) (gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.9) ) #140-Ubuntu SMP Mon Feb 12 21:22:43 UTC 2018 (Ubuntu 4.4.0-116.140-generic 4.4.98)
 7월 29 16:25:57 VirtualBox kernel: KERNEL supported cpus:
 7월 29 16:25:57 VirtualBox kernel:   Intel GenuineIntel

view current boot log

$ journalctl -b

view specific time log

$ journalctl --since "2019-01-10" --until "2019-01-11 03:00"

view log by service

$ journalctl -u [service name]

tail log

$ journalctl -u [service name] -f