On 22 February 2018 at 20:20, Bryan Quigley <bryan.quig...@canonical.com> wrote:
> "The journald daemon has limits set for logs, meaning they will be rotated
> and discarded and should not cause out of disk-space errors."
> What are they? AFAICT it only has limits on the number of files, but
> not how big they can overall become.
> I'm also thinking that the duplicate writing of logs could cause other
> regressions, one example being where high disk throughput is ongoing and many
> things being written to the logs. Thoughts?
The performance impact on disk throughput should not be significant,
as journald still throttles and caches the log messages before
flushing them to disk and still forwards them to rsyslog as it did
before. The performance impact depends on the workload, and there is a
reduction of runtime memory used as well, which helps with throughput
by increasing available io cache buffers.
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Touch seeded packages, which is subscribed to systemd in Ubuntu.
systemd journal should be persistent by default: /var/log/journal
should be created
Status in systemd package in Ubuntu:
Status in systemd source package in Xenial:
Status in systemd source package in Zesty:
Status in systemd source package in Artful:
Status in systemd source package in Bionic:
* System logs are lost across reboots because they are not stored
* Fresh installations, or upgrades to this version of systemd, should create
/var/log/journal and trigger automatic persistent logs.
* Users may choose to remove said directory, or disable persistent logging
* Persistent logging by default will cause logs to be flushed from
/run to /var/log, meaning there will be less RAM used (/run is tmpfs
backed), but increased disk usage (in /var/log). The journald daemon
has limits set for logs, meaning they will be rotated and discarded
and should not cause out of disk-space errors.
* Original bug report
After upgrading 14.04 -> 16.04, key services are now running on
systemd and using the systemd journal for logging. In 14.04, key
system logs like /var/log/messages and /var/log/syslog were
persistent, but after the upgrade to 16.04 there has a been a
regression of sorts: Logs sent to systemd's journald are now being
thrown away during reboots.
This behavior is controlled by the `Storage=` option in
`/etc/systemd/journald.conf`. The default setting is `Storage=auto`
which will persist logs in `/var/log/journal/`, *only if the directory
already exists*. But the directory was not created as part of the
14.04 -> 16.04 upgrade, so logging was being lost for a while before I
realized what was happening.
This issue could be solved by either creating /var/log/journal or
changing the default Storage behavior to `Storage=persistent`, which
would create the directory if need be.
## Related reference
* `systemd` currently compounds the issue by having ["journal --disk-usage"
report memory usage as disk
usage](https://github.com/systemd/systemd/issues/4059), giving the impression
that the disk is being used for logging when it isn't.
* [User wonders where to find logs from previous boots, unaware that the
logs were thrown
## Recommended fix
Restoring persistent logging as the default is recommended.
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