SYSTEMD-JOURNALD.SERVICE(8)systemd-journald.serviceSYSTEMD-JOURNALD.SERVICE(8)
NAME
systemd-journald.service, systemd-journald.socket, systemd-journald-
dev-log.socket, systemd-journald-audit.socket, systemd-
journald@.service, systemd-journald@.socket, systemd-journald-
varlink@.socket, systemd-journald - Journal service
SYNOPSIS
systemd-journald.service
systemd-journald.socket
systemd-journald-dev-log.socket
systemd-journald-audit.socket
systemd-journald@.service
systemd-journald@.socket
systemd-journald-varlink@.socket
/lib/systemd/systemd-journald
DESCRIPTION
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 a variety of sources:
o Kernel log messages, via kmsg
o Simple system log messages, via the libc syslog(3) call
o Structured system log messages via the native Journal API, see
sd_journal_print(3) and Native Journal Protocol[1]
o Standard output and standard error of service units. For further
details see below.
o Audit records, originating from the kernel audit subsystem
The daemon will implicitly collect numerous metadata fields for each
log messages in a secure and unfakeable way. See systemd.journal-
fields(7) for more information about the collected metadata.
Log data collected by the journal is primarily text-based but can also
include binary data where necessary. Individual fields making up a log
record stored in the journal may be up to 2-1 bytes in size.
The journal service stores log data either persistently below
/var/log/journal or in a volatile way below /run/log/journal/ (in the
latter case it is lost at reboot). By default, log data is stored
persistently if /var/log/journal/ exists during boot, with an implicit
fallback to volatile storage otherwise. Use Storage= in
journald.conf(5) to configure where log data is placed, independently
of the existence of /var/log/journal/.
Note that journald will initially use volatile storage, until a call to
journalctl --flush (or sending SIGUSR1 to journald) will cause it to
switch to persistent logging (under the conditions mentioned above).
This is done automatically on boot via "systemd-journal-flush.service".
On systems where /var/log/journal/ does not exist yet but where
persistent logging is desired (and the default journald.conf is used),
it is sufficient to create the directory, and ensure it has the correct
access modes and ownership:
mkdir -p /var/log/journal
systemd-tmpfiles --create --prefix /var/log/journal
See journald.conf(5) for information about the configuration of this
service.
STREAM LOGGING
The systemd service manager invokes all service processes with standard
output and standard error connected to the journal by default. This
behaviour may be altered via the StandardOutput=/StandardError= unit
file settings, see systemd.exec(5) for details. The journal converts
the log byte stream received this way into individual log records,
splitting the stream at newline ("\n", ASCII 10) and NUL bytes.
If systemd-journald.service is stopped, the stream connections
associated with all services are terminated. Further writes to those
streams by the service will result in EPIPE errors. In order to react
gracefully in this case it is recommended that programs logging to
standard output/error ignore such errors. If the SIGPIPE UNIX signal
handler is not blocked or turned off, such write attempts will also
result in such process signals being generated, see signal(7). To
mitigate this issue, systemd service manager explicitly turns off the
SIGPIPE signal for all invoked processes by default (this may be
changed for each unit individually via the IgnoreSIGPIPE= option, see
systemd.exec(5) for details). After the standard output/standard error
streams have been terminated they may not be recovered until the
services they are associated with are restarted. Note that during
normal operation, systemd-journald.service stores copies of the file
descriptors for those streams in the service manager. If
systemd-journald.service is restarted using systemctl restart or
equivalent operation instead of a pair of separate systemctl stop and
systemctl start commands (or equivalent operations), these stream
connections are not terminated and survive the restart. It is thus safe
to restart systemd-journald.service, but stopping it is not
recommended.
Note that the log record metadata for records transferred via such
standard output/error streams reflect the metadata of the peer the
stream was originally created for. If the stream connection is passed
on to other processes (such as further child processes forked off the
main service process), the log records will not reflect their metadata,
but will continue to describe the original process. This is different
from the other logging transports listed above, which are inherently
record based and where the metadata is always associated with the
individual record.
In addition to the implicit standard output/error logging of services,
stream logging is also available via the systemd-cat(1) command line
tool.
Currently, the number of parallel log streams systemd-journald will
accept is limited to 4096. When this limit is reached further log
streams may be established but will receive EPIPE right from the
beginning.
JOURNAL NAMESPACES
Journal 'namespaces' are both a mechanism for logically isolating the
log stream of projects consisting of one or more services from the rest
of the system and a mechanism for improving performance. Multiple
journal namespaces may exist simultaneously, each defining its own,
independent log stream managed by its own instance of systemd-journald.
Namespaces are independent of each other, both in the data store and in
the IPC interface. By default only a single 'default' namespace exists,
managed by systemd-journald.service (and its associated socket units).
Additional namespaces are created by starting an instance of the
systemd-journald@.service service template. The instance name is the
namespace identifier, which is a short string used for referencing the
journal namespace. Service units may be assigned to a specific journal
namespace through the LogNamespace= unit file setting, see
systemd.exec(5) for details. The --namespace= switch of journalctl(1)
may be u'
SYSTEMD-JOURNALD.SERVICE(8)systemd-journald.serviceSYSTEMD-JOURNALD.SERVICE(8)
NAME
systemd-journald.service, systemd-journald.socket, systemd-journald-
dev-log.socket, systemd-journald-audit.socket, systemd-
journald@.service, systemd-journald@.socket, systemd-journald-
varlink@.socket, systemd-journald - Journal service
SYNOPSIS
systemd-journald.service
systemd-journald.socket
systemd-journald-dev-log.socket
systemd-journald-audit.socket
systemd-journald@.service
systemd-journald@.socket
systemd-journald-varlink@.socket
/lib/systemd/systemd-journald
DESCRIPTION
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 a variety of sources:
o Kernel log messages, via kmsg
o Simple system log messages, via the libc syslog(3) call
o Structured system log messages via the native Journal API, see
sd_journal_print(3) and Native Journal Protocol[1]
o Standard output and standard error of service units. For further
details see below.
o Audit records, originating from the kernel audit subsystem
The daemon will implicitly collect numerous metadata fields for each
log messages in a secure and unfakeable way. See systemd.journal-
fields(7) for more information about the collected metadata.
Log data collected by the journal is primarily text-based but can also
include binary data where necessary. Individual fields making up a log
record stored in the journal may be up to 2-1 bytes in size.
The journal service stores log data either persistently below
/var/log/journal or in a volatile way below /run/log/journal/ (in the
latter case it is lost at reboot). By default, log data is stored
persistently if /var/log/journal/ exists during boot, with an implicit
fallback to volatile storage otherwise. Use Storage= in
journald.conf(5) to configure where log data is placed, independently
of the existence of /var/log/journal/.
Note that journald will initially use volatile storage, until a call to
journalctl --flush (or sending SIGUSR1 to journald) will cause it to
switch to persistent logging (under the conditions mentioned above).
This is done automatically on boot via "systemd-journal-flush.service".
On systems where /var/log/journal/ does not exist yet but where
persistent logging is desired (and the default journald.conf is used),
it is sufficient to create the directory, and ensure it has the correct
access modes and ownership:
mkdir -p /var/log/journal
systemd-tmpfiles --create --prefix /var/log/journal
See journald.conf(5) for information about the configuration of this
service.
STREAM LOGGING
The systemd service manager invokes all service processes with standard
output and standard error connected to the journal by default. This
behaviour may be altered via the StandardOutput=/StandardError= unit
file settings, see systemd.exec(5) for details. The journal converts
the log byte stream received this way into individual log records,
splitting the stream at newline ("\n", ASCII 10) and NUL bytes.
If systemd-journald.service is stopped, the stream connections
associated with all services are terminated. Further writes to those
streams by the service will result in EPIPE errors. In order to react
gracefully in this case it is recommended that programs logging to
standard output/error ignore such errors. If the SIGPIPE UNIX signal
handler is not blocked or turned off, such write attempts will also
result in such process signals being generated, see signal(7). To
mitigate this issue, systemd service manager explicitly turns off the
SIGPIPE signal for all invoked processes by default (this may be
changed for each unit individually via the IgnoreSIGPIPE= option, see
systemd.exec(5) for details). After the standard output/standard error
streams have been terminated they may not be recovered until the
services they are associated with are restarted. Note that during
normal operation, systemd-journald.service stores copies of the file
descriptors for those streams in the service manager. If
systemd-journald.service is restarted using systemctl restart or
equivalent operation instead of a pair of separate systemctl stop and
systemctl start commands (or equivalent operations), these stream
connections are not terminated and survive the restart. It is thus safe
to restart systemd-journald.service, but stopping it is not
recommended.
Note that the log record metadata for records transferred via such
standard output/error streams reflect the metadata of the peer the
stream was originally created for. If the stream connection is passed
on to other processes (such as further child processes forked off the
main service process), the log records will not reflect their metadata,
but will continue to describe the original process. This is different
from the other logging transports
systemd 252 SYSTEMD-JOURNALD.SERVICE(8)
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