[systemd-devel] Q: journalctl -b -g logrotate

[Mantas Mikulėnas]

On Tue, Apr 5, 2022 at 9:36 AM Ulrich Windl <
Ulrich.Windl at rz.uni-regensburg.de> wrote:

> Hi!
>
> I have two questions for "journalctl -b -g logrotate":
>
> 1) I'm unsure what the exact rules for matching a "-g expression" are:
> Some kernel messages are matched, others not.
>

All entries with a MESSAGE= are matched (after doing until/since/boot-id
checks). They might still be hidden for other reasons though, e.g. messages
containing weird escape characters (or accidental binary data) will be
hidden unless you use -a.


> 2) When the -b restricts messages to the current boot, why is output shown
> like this?:
> # journalctl -b -g logrotate
> -- Logs begin at Wed 2020-11-25 11:27:53 CET, end at Tue 2022-04-05
> 08:01:02 CEST. --
>
> I mean the boot was definitely in 2022, so I think the message is not
> really helpful. Why not show the date and time when the search starts (i.e.
> boot time)?
>

There's no such message in the current systemd version. See
https://github.com/systemd/systemd/pull/21775.


>
> The next thing is "-k": If I supply it, kernel messages are _not_ found:
> # journalctl -S 2022-04-02 -k | grep "OCFS2:" |head
> # journalctl -S 2022-04-02 | grep "OCFS2:" |head
> Apr 02 02:00:06 h18 kernel: OCFS2: ERROR (device dm-17):
> ocfs2_validate_gd_self: Group descriptor #209970 has bad signature EXBLK01
> Apr 02 02:00:06 h18 kernel: OCFS2: File system is now read-only.
> Apr 02 02:00:07 h18 kernel: OCFS2: ERROR (device dm-17):
> ocfs2_validate_gd_self: Group descriptor #209817 has bad signature EXBLK01
> Apr 02 02:00:07 h18 kernel: OCFS2: ERROR (device dm-17):
> ocfs2_validate_gd_self: Group descriptor #209946 has bad signature EXBLK01
>
> So can I find kernel messages from previous boots?
>

`journalctl -k` is meant to imitate dmesg (except with correct timestamps),
so it shows the current boot only. You can use _TRANSPORT=kernel to filter
for kernel messages if you don't want that.

$ journalctl _TRANSPORT=kernel -g BogoMIPS

-- 
Mantas Mikulėnas
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/systemd-devel/attachments/20220405/0dfa09ec/attachment.htm>