journalctl

Question 1

journalctl

Help pages 1-2

Answer 1

Used to query the contents of the systemd journal logs.

Question 2

journalctl -b [ID] [+- offset]

Answer 2

-b Show messages from a specific boot.

[ID]

boot ID can be entered

[+- offset]

• 1 would display last boot
• 2 would display boot before last

Question 3

journalctl -S -U

–since –until

Answer 3

-S –since

Shows logs with timestamps since the date chosen. The format can be in 00:00:00 or string format.

Question 4

journalctl –list-boots

Answer 4

–list-boots

Lists the previous boot numbers

Question 5

journalctl -u

Answer 5

-u

Shows logs filtered by systemd unit.

example: nginx.service

Question 6

journalctl -f

Answer 6

-f –follow

Shows only the most recent log entries

Question 7

journalctl -r

Answer 7

-r –reverse

Reverses output so newest entries are first.