wiki/notebook/cli.journalctl.org

:PROPERTIES:
:ID:       941e0a85-1bb4-45be-a729-1b577c7ee317
:END:
#+title: Command line: journalctl
#+date: "2021-05-20 23:07:39 +08:00"
#+date_modified: "2021-09-01 22:39:16 +08:00"
#+language: en
#+property: header-args  :results none


The logging daemon of systemd (see [[id:d83c099a-fc11-4ccc-b265-4de97c85dcbe][systemd-journald]]).
Not only it can view your logs, you can ask to view specific logs and delete some of them.

For more information, see =journalctl.1= manual page.


* Options

- =-b, --boot [ID][+OFFSET]= shows the logs starting from given boot time (or current boot if empty).
- =-e, --pager-end= to go to the end of the logs.
- =-f, --follow= watches the logs.
- =-k, --dmesg= prints the logs from the kernel.
- =--list-boots= prints a list of boots useful for knowing the boot logs from =-b=.
- =--user-unit= shows logs from a user unit.
- =-u, --unit [UNIT]= shows the logs of a system unit.
- =--vacuum-time [TIMESPAN]= deletes logs older than the specified timespan [fn:: View =systemd.time.5= for more information.].
- =-x, --catalog= prints helpful messages such as the documentation URIs.


* Examples

This tool is already comprehensive.
Needs a comprehensive database of examples to fight against this scope.


** Watch the logs from a specific unit at boot time

#+begin_src
journalctl --user-unit borgbackup.service -fb
#+end_src


** Delete the logs older than a month

#+begin_src
journalctl --vacuum-time=1m
#+end_src


** View the latest logs with helpful messages

#+begin_src
journalctl -xe
#+end_src


** Get the logs of a service unit from 2 boots ago

#+begin_src
journalctl --boot -2 --user-unit borgbackup@personal-drive.service
#+end_src
Merge evergreen notes into the notebook Now, it's all under the notebook umbrella. Seems to be appropriate as it is just my notes after all. I also updated some notes from there. I didn't keep track of what it is this time. Something about more learning notes extracted from my "Learning how to learn" course notes and then some. Lack of time and hurriness just makes it difficult to track but it should be under version control already. 2021-07-21 08:28:07 +00:00			`:PROPERTIES:`
			`:ID: 941e0a85-1bb4-45be-a729-1b577c7ee317`
			`:END:`
Make the command line notes consistent Just the title anyways. It makes easier to find aside from the file name and also makes it clear in case I refer to them from other documents. 2021-06-20 02:22:13 +00:00			`#+title: Command line: journalctl`
Update my cards and my notebook Some additional notes on some tools I seem to use more frequently. Nothing unusual here. 2021-05-21 04:09:51 +00:00			`#+date: "2021-05-20 23:07:39 +08:00"`
Update notebook as of 2021-10-09 Welp, I rarely take notes nowadays due to more specialized work and stuff. Though, I should have more incentives for writing. In other words, I'm just lazy. ;p More free-thinking morning sessions should be done soon. 2021-10-09 10:14:46 +00:00			`#+date_modified: "2021-09-01 22:39:16 +08:00"`
Update my cards and my notebook Some additional notes on some tools I seem to use more frequently. Nothing unusual here. 2021-05-21 04:09:51 +00:00			`#+language: en`
			`#+property: header-args :results none`


Update notebook as of 2021-08-27 I forgot. I should process more notes starting tomorrow. ;p 2021-08-27 14:24:00 +00:00			`The logging daemon of systemd (see [[id:d83c099a-fc11-4ccc-b265-4de97c85dcbe][systemd-journald]]).`
Update my cards and my notebook Some additional notes on some tools I seem to use more frequently. Nothing unusual here. 2021-05-21 04:09:51 +00:00			`Not only it can view your logs, you can ask to view specific logs and delete some of them.`

			`For more information, see =journalctl.1= manual page.`




			`* Options`

Update notebook as of 2021-10-09 Welp, I rarely take notes nowadays due to more specialized work and stuff. Though, I should have more incentives for writing. In other words, I'm just lazy. ;p More free-thinking morning sessions should be done soon. 2021-10-09 10:14:46 +00:00			`- =-b, --boot [ID][+OFFSET]= shows the logs starting from given boot time (or current boot if empty).`
			`- =-e, --pager-end= to go to the end of the logs.`
			`- =-f, --follow= watches the logs.`
			`- =-k, --dmesg= prints the logs from the kernel.`
			`- =--list-boots= prints a list of boots useful for knowing the boot logs from =-b=.`
			`- =--user-unit= shows logs from a user unit.`
			`- =-u, --unit [UNIT]= shows the logs of a system unit.`
			`- =--vacuum-time [TIMESPAN]= deletes logs older than the specified timespan [fn:: View =systemd.time.5= for more information.].`
			`- =-x, --catalog= prints helpful messages such as the documentation URIs.`
Update my cards and my notebook Some additional notes on some tools I seem to use more frequently. Nothing unusual here. 2021-05-21 04:09:51 +00:00



			`* Examples`

			`This tool is already comprehensive.`
			`Needs a comprehensive database of examples to fight against this scope.`


			`** Watch the logs from a specific unit at boot time`

Update structured notes on anything I use today 2021-05-30 13:33:19 +00:00			`#+begin_src`
Update my cards and my notebook Some additional notes on some tools I seem to use more frequently. Nothing unusual here. 2021-05-21 04:09:51 +00:00			`journalctl --user-unit borgbackup.service -fb`
			`#+end_src`


			`** Delete the logs older than a month`

Update structured notes on anything I use today 2021-05-30 13:33:19 +00:00			`#+begin_src`
Update my cards and my notebook Some additional notes on some tools I seem to use more frequently. Nothing unusual here. 2021-05-21 04:09:51 +00:00			`journalctl --vacuum-time=1m`
			`#+end_src`


			`** View the latest logs with helpful messages`

Update structured notes on anything I use today 2021-05-30 13:33:19 +00:00			`#+begin_src`
Update my cards and my notebook Some additional notes on some tools I seem to use more frequently. Nothing unusual here. 2021-05-21 04:09:51 +00:00			`journalctl -xe`
			`#+end_src`
Update notebook as of 2021-10-09 Welp, I rarely take notes nowadays due to more specialized work and stuff. Though, I should have more incentives for writing. In other words, I'm just lazy. ;p More free-thinking morning sessions should be done soon. 2021-10-09 10:14:46 +00:00

			`** Get the logs of a service unit from 2 boots ago`

			`#+begin_src`
			`journalctl --boot -2 --user-unit borgbackup@personal-drive.service`
			`#+end_src`