systemd-journald.service.8 5.39 KB
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.TH "SYSTEMD\-JOURNALD\&.SERVICE" "8" "" "systemd 215" "systemd-journald.service"
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.SH "NAME"
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systemd-journald.service, systemd-journald.socket, systemd-journald-dev-log.socket, systemd-journald \- Journal service
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.SH "SYNOPSIS"
.PP
systemd\-journald\&.service
.PP
systemd\-journald\&.socket
.PP
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systemd\-journald\-dev\-log\&.socket
.PP
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/usr/lib/systemd/systemd\-journald
.SH "DESCRIPTION"
.PP
systemd\-journald
is a system service that collects and stores logging data\&. It creates and maintains structured, indexed journals based on logging information that is received from the kernel, from user processes via the libc
\fBsyslog\fR(3)
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call, from standard input and standard error of system services or via its native API\&. It will implicitly collect numerous metadata fields for each log messages in a secure and unfakeable way\&. See
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\fBsystemd.journal-fields\fR(7)
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for more information about the collected metadata\&.
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.PP
Log data collected by the journal is primarily text\-based but can also include binary data where necessary\&. All objects stored in the journal can be up to 2^64\-1 bytes in size\&.
.PP
By default, the journal stores log data in
/run/log/journal/\&. Since
/run/
is volatile, log data is lost at reboot\&. To make the data persistent, it is sufficient to create
/var/log/journal/
where
systemd\-journald
will then store the data\&.
.PP
systemd\-journald
will forward all received log messages to the
\fBAF_UNIX\fR\fBSOCK_DGRAM\fR
socket
/run/systemd/journal/syslog, if it exists, which may be used by Unix syslog daemons to process the data further\&.
.PP
See
\fBjournald.conf\fR(5)
for information about the configuration of this service\&.
.SH "SIGNALS"
.PP
SIGUSR1
.RS 4
Request that journal data from
/run/
is flushed to
/var/
in order to make it persistent (if this is enabled)\&. This must be used after
/var/
is mounted, as otherwise log data from
/run
is never flushed to
/var
regardless of the configuration\&.
.RE
.PP
SIGUSR2
.RS 4
Request immediate rotation of the journal files\&.
.RE
.SH "KERNEL COMMAND LINE"
.PP
A few configuration parameters from
journald\&.conf
may be overridden on the kernel command line:
.PP
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\fIsystemd\&.journald\&.forward_to_syslog=\fR, \fIsystemd\&.journald\&.forward_to_kmsg=\fR, \fIsystemd\&.journald\&.forward_to_console=\fR, \fIsystemd\&.journald\&.forward_to_wall=\fR
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.RS 4
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Enables/disables forwarding of collected log messages to syslog, the kernel log buffer, the system console or wall\&.
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.sp
See
\fBjournald.conf\fR(5)
for information about these settings\&.
.RE
.SH "ACCESS CONTROL"
.PP
Journal files are, by default, owned and readable by the
"systemd\-journal"
system group but are not writable\&. Adding a user to this group thus enables her/him to read the journal files\&.
.PP
By default, each logged in user will get her/his own set of journal files in
/var/log/journal/\&. These files will not be owned by the user, however, in order to avoid that the user can write to them directly\&. Instead, file system ACLs are used to ensure the user gets read access only\&.
.PP
Additional users and groups may be granted access to journal files via file system access control lists (ACL)\&. Distributions and administrators may choose to grant read access to all members of the
"wheel"
and
"adm"
system groups with a command such as the following:
.sp
.if n \{\
.RS 4
.\}
.nf
# setfacl \-Rnm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/
.fi
.if n \{\
.RE
.\}
.PP
Note that this command will update the ACLs both for existing journal files and for future journal files created in the
/var/log/journal/
directory\&.
.SH "FILES"
.PP
/etc/systemd/journald\&.conf
.RS 4
Configure
\fBsystemd\-journald\fR
behaviour\&. See
\fBjournald.conf\fR(5)\&.
.RE
.PP
/run/log/journal/\fImachine\-id\fR/*\&.journal, /run/log/journal/\fImachine\-id\fR/*\&.journal~, /var/log/journal/\fImachine\-id\fR/*\&.journal, /var/log/journal/\fImachine\-id\fR/*\&.journal~
.RS 4
\fBsystemd\-journald\fR
writes entries to files in
/run/log/journal/\fImachine\-id\fR/
or
/var/log/journal/\fImachine\-id\fR/
with the
"\&.journal"
suffix\&. If the daemon is stopped uncleanly, or if the files are found to be corrupted, they are renamed using the
"\&.journal~"
suffix, and
\fBsystemd\-journald\fR
starts writing to a new file\&.
/run
is used when
/var/log/journal
is not available, or when
\fBStorage=volatile\fR
is set in the
\fBjournald.conf\fR(5)
configuration file\&.
.RE
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1),
\fBjournalctl\fR(1),
\fBjournald.conf\fR(5),
\fBsystemd.journal-fields\fR(7),
\fBsd-journal\fR(3),
\fBsetfacl\fR(1),
\fBpydoc systemd\&.journal\fR\&.