journald.conf(5)
NAME
journald.conf, journald.conf.d - Journal service configuration files
SYNOPSIS
/etc/systemd/journald.conf /etc/systemd/journald.conf.d/*.conf /run/systemd/journald.conf.d/*.conf /usr/lib/systemd/journald.conf.d/*.conf
DESCRIPTION
These files configure various parameters of the systemd journal service, systemd-journald.service(8).
CONFIGURATION DIRECTORIES AND PRECEDENCE
The default configuration is defined during compilation, so a configuration file is only needed when it is necessary to deviate from those defaults. By default, the configuration file in /etc/systemd/ contains commented out entries showing the defaults as a guide to the administrator. This file can be edited to create local overrides. When packages need to customize the configuration, they can install configuration snippets in /usr/lib/systemd/*.conf.d/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. The main configuration file is read before any of the configuration directories, and has the lowest precedence; entries in a file in any configuration directory override entries in the single configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of which of the subdirectories they reside in. If multiple files specify the same option, the entry in the file with the lexicographically latest name takes precedence. It is recommended to prefix all filenames in those subdirectories with a two-digit number and a dash, to simplify the ordering of the files. To disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in the configuration directory in /etc/, with the same filename as the vendor configuration file.
OPTIONS
All options are configured in the "[Journal]" section:
Storage=
Controls where to store journal data. One of "volatile",
"persistent", "auto" and "none". If "volatile", journal log data
will be stored only in memory, i.e. below the /run/log/journal
hierarchy (which is created if needed). If "persistent", data will
be stored preferably on disk, i.e. below the /var/log/journal
hierarchy (which is created if needed), with a fallback to
/run/log/journal (which is created if needed), during early boot
and if the disk is not writable. "auto" is similar to "persistent"
but the directory /var/log/journal is not created if needed, so
that its existence controls where log data goes. "none" turns off
all storage, all log data received will be dropped. Forwarding to
other targets, such as the console, the kernel log buffer, or a
syslog socket will still work however. Defaults to "auto".
Compress=
Takes a boolean value. If enabled (the default), data objects that
shall be stored in the journal and are larger than a certain
threshold are compressed before they are written to the file
system.
Seal=
Takes a boolean value. If enabled (the default), and a sealing key
is available (as created by journalctl(1)'s --setup-keys command),
Forward Secure Sealing (FSS) for all persistent journal files is
enabled. FSS is based on Seekable Sequential Key Generators[1] by
G. A. Marson and B. Poettering (doi:10.1007/978-3-642-40203-6_7)
and may be used to protect journal files from unnoticed alteration.
SplitMode=
Controls whether to split up journal files per user, either "uid"
or "none". Split journal files are primarily useful for access
control: on UNIX/Linux access control is managed per file, and the
journal daemon will assign users read access to their journal
files. If "uid", all regular users will each get their own journal
files, and system users will log to the system journal. If "none",
journal files are not split up by user and all messages are instead
stored in the single system journal. In this mode unprivileged
users generally do not have access to their own log data. Note that
splitting up journal files by user is only available for journals
stored persistently. If journals are stored on volatile storage
(see Storage= above), only a single journal file is used. Defaults
to "uid".
RateLimitIntervalSec=, RateLimitBurst=
Configures the rate limiting that is applied to all messages
generated on the system. If, in the time interval defined by
RateLimitIntervalSec=, more messages than specified in
RateLimitBurst= are logged by a service, all further messages
within the interval are dropped until the interval is over. A
message about the number of dropped messages is generated. This
rate limiting is applied per-service, so that two services which
log do not interfere with each other's limits. Defaults to 1000
messages in 30s. The time specification for RateLimitIntervalSec=
may be specified in the following units: "s", "min", "h", "ms",
"us". To turn off any kind of rate limiting, set either value to 0.
SystemMaxUse=, SystemKeepFree=, SystemMaxFileSize=, SystemMaxFiles=,
RuntimeMaxUse=, RuntimeKeepFree=, RuntimeMaxFileSize=, RuntimeMaxFiles=
Enforce size limits on the journal files stored. The options
prefixed with "System" apply to the journal files when stored on a
persistent file system, more specifically /var/log/journal. The
options prefixed with "Runtime" apply to the journal files when
stored on a volatile in-memory file system, more specifically
/run/log/journal. The former is used only when /var is mounted,
writable, and the directory /var/log/journal exists. Otherwise,
only the latter applies. Note that this means that during early
boot and if the administrator disabled persistent logging, only the
latter options apply, while the former apply if persistent logging
is enabled and the system is fully booted up. journalctl and
systemd-journald ignore all files with names not ending with
".journal" or ".journal~", so only such files, located in the
appropriate directories, are taken into account when calculating
current disk usage.
SystemMaxUse= and RuntimeMaxUse= control how much disk space the
journal may use up at most. SystemKeepFree= and RuntimeKeepFree=
control how much disk space systemd-journald shall leave free for
other uses. systemd-journald will respect both limits and use the
smaller of the two values.
The first pair defaults to 10% and the second to 15% of the size of
the respective file system, but each value is capped to 4G. If the
file system is nearly full and either SystemKeepFree= or
RuntimeKeepFree= are violated when systemd-journald is started, the
limit will be raised to the percentage that is actually free. This
means that if there was enough free space before and journal files
were created, and subsequently something else causes the file
system to fill up, journald will stop using more space, but it will
not be removing existing files to reduce the footprint again,
either.
SystemMaxFileSize= and RuntimeMaxFileSize= control how large
individual journal files may grow at most. This influences the
granularity in which disk space is made available through rotation,
i.e. deletion of historic data. Defaults to one eighth of the
values configured with SystemMaxUse= and RuntimeMaxUse=, so that
usually seven rotated journal files are kept as history.
Specify values in bytes or use K, M, G, T, P, E as units for the
specified sizes (equal to 1024, 1024, ... bytes). Note that size
limits are enforced synchronously when journal files are extended,
and no explicit rotation step triggered by time is needed.
SystemMaxFiles= and RuntimeMaxFiles= control how many individual
journal files to keep at most. Note that only archived files are
deleted to reduce the number of files until this limit is reached;
active files will stay around. This means that, in effect, there
might still be more journal files around in total than this limit
after a vacuuming operation is complete. This setting defaults to
100.
MaxFileSec=
The maximum time to store entries in a single journal file before
rotating to the next one. Normally, time-based rotation should not
be required as size-based rotation with options such as
SystemMaxFileSize= should be sufficient to ensure that journal
files do not grow without bounds. However, to ensure that not too
much data is lost at once when old journal files are deleted, it
might make sense to change this value from the default of one
month. Set to 0 to turn off this feature. This setting takes time
values which may be suffixed with the units "year", "month",
"week", "day", "h" or "m" to override the default time unit of
seconds.
MaxRetentionSec=
The maximum time to store journal entries. This controls whether
journal files containing entries older then the specified time span
are deleted. Normally, time-based deletion of old journal files
should not be required as size-based deletion with options such as
SystemMaxUse= should be sufficient to ensure that journal files do
not grow without bounds. However, to enforce data retention
policies, it might make sense to change this value from the default
of 0 (which turns off this feature). This setting also takes time
values which may be suffixed with the units "year", "month",
"week", "day", "h" or " m" to override the default time unit of
seconds.
SyncIntervalSec=
The timeout before synchronizing journal files to disk. After
syncing, journal files are placed in the OFFLINE state. Note that
syncing is unconditionally done immediately after a log message of
priority CRIT, ALERT or EMERG has been logged. This setting hence
applies only to messages of the levels ERR, WARNING, NOTICE, INFO,
DEBUG. The default timeout is 5 minutes.
ForwardToSyslog=, ForwardToKMsg=, ForwardToConsole=, ForwardToWall=
Control whether log messages received by the journal daemon shall
be forwarded to a traditional syslog daemon, to the kernel log
buffer (kmsg), to the system console, or sent as wall messages to
all logged-in users. These options take boolean arguments. If
forwarding to syslog is enabled but nothing reads messages from the
socket, forwarding to syslog has no effect. By default, only
forwarding to syslog and wall is enabled. These settings may be
overridden at boot time with the kernel command line options
"systemd.journald.forward_to_syslog",
"systemd.journald.forward_to_kmsg",
"systemd.journald.forward_to_console", and
"systemd.journald.forward_to_wall". If the option name is specified
without "=" and the following argument, true is assumed. Otherwise,
the argument is parsed as a boolean. When forwarding to the
console, the TTY to log to can be changed with TTYPath=, described
below.
MaxLevelStore=, MaxLevelSyslog=, MaxLevelKMsg=, MaxLevelConsole=,
MaxLevelWall=
Controls the maximum log level of messages that are stored on disk,
forwarded to syslog, kmsg, the console or wall (if that is enabled,
see above). As argument, takes one of "emerg", "alert", "crit",
"err", "warning", "notice", "info", "debug", or integer values in
the range of 0--7 (corresponding to the same levels). Messages equal
or below the log level specified are stored/forwarded, messages
above are dropped. Defaults to "debug" for MaxLevelStore= and
MaxLevelSyslog=, to ensure that the all messages are written to
disk and forwarded to syslog. Defaults to "notice" for
MaxLevelKMsg=, "info" for MaxLevelConsole=, and "emerg" for
MaxLevelWall=. These settings may be overridden at boot time with
the kernel command line options
"systemd.journald.max_level_store=",
"systemd.journald.max_level_syslog=",
"systemd.journald.max_level_kmsg=",
"systemd.journald.max_level_console=",
"systemd.journald.max_level_wall=".
TTYPath=
Change the console TTY to use if ForwardToConsole=yes is used.
Defaults to /dev/console.
FORWARDING TO TRADITIONAL SYSLOG DAEMONS
Journal events can be transferred to a different logging daemon in two different ways. With the first method, messages are immediately forwarded to a socket (/run/systemd/journal/syslog), where the traditional syslog daemon can read them. This method is controlled by the ForwardToSyslog= option. With a second method, a syslog daemon behaves like a normal journal client, and reads messages from the journal files, similarly to journalctl(1). With this, messages do not have to be read immediately, which allows a logging daemon which is only started late in boot to access all messages since the start of the system. In addition, full structured meta-data is available to it. This method of course is available only if the messages are stored in a journal file at all. So it will not work if Storage=none is set. It should be noted that usually the second method is used by syslog daemons, so the Storage= option, and not the ForwardToSyslog= option, is relevant for them.
SEE ALSO
systemd(1), systemd-journald.service(8), journalctl(1), systemd.journal-fields(7), systemd-system.conf(5)
NOTES
1. Seekable Sequential Key Generators
https://eprint.iacr.org/2013/397
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