systemd-journald.service(8)

NAME

   systemd-journald.service, systemd-journald.socket, systemd-journald-
   dev-log.socket, systemd-journald-audit.socket, systemd-journald -
   Journal service

SYNOPSIS

   systemd-journald.service

   systemd-journald.socket

   systemd-journald-dev-log.socket

   systemd-journald-audit.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:

   ·   Kernel log messages, via kmsg

   ·   Simple system log messages, via the libc syslog(3) call

   ·   Structured system log messages via the native Journal API, see
       sd_journal_print(4)

   ·   Standard output and standard error of system services

   ·   Audit records, via the 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. All objects stored in the journal
   can be up to 2^64-1 bytes in size.

   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:

       mkdir -p /var/log/journal
       systemd-tmpfiles --create --prefix /var/log/journal

   See journald.conf(5) for information about the configuration of this
   service.

SIGNALS

   SIGUSR1
       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. The journalctl --flush
       command uses this signal to request flushing of the journal files,
       and then waits for the operation to complete. See journalctl(1) for
       details.

   SIGUSR2
       Request immediate rotation of the journal files. The journalctl
       --rotate command uses this signal to request journal file rotation.

   SIGRTMIN+1
       Request that all unwritten log data is written to disk. The
       journalctl --sync command uses this signal to trigger journal
       synchronization, and then waits for the operation to complete.

KERNEL COMMAND LINE

   A few configuration parameters from journald.conf may be overridden on
   the kernel command line:

   systemd.journald.forward_to_syslog=, systemd.journald.forward_to_kmsg=,
   systemd.journald.forward_to_console=, systemd.journald.forward_to_wall=
       Enables/disables forwarding of collected log messages to syslog,
       the kernel log buffer, the system console or wall.

       See journald.conf(5) for information about these settings.

ACCESS CONTROL

   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.

   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.

   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:

       # setfacl -Rnm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/

   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.

FILES

   /etc/systemd/journald.conf
       Configure systemd-journald behavior. See journald.conf(5).

   /run/log/journal/machine-id/*.journal,
   /run/log/journal/machine-id/*.journal~,
   /var/log/journal/machine-id/*.journal,
   /var/log/journal/machine-id/*.journal~
       systemd-journald writes entries to files in
       /run/log/journal/machine-id/ or /var/log/journal/machine-id/ 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 systemd-journald starts writing to a new
       file.  /run is used when /var/log/journal is not available, or when
       Storage=volatile is set in the journald.conf(5) configuration file.

   /dev/kmsg, /dev/log, /run/systemd/journal/dev-log,
   /run/systemd/journal/socket, /run/systemd/journal/stdout
       Sockets and other paths that systemd-journald will listen on that
       are visible in the file system. In addition to these, journald can
       listen for audit events using netlink.

SEE ALSO

   systemd(1), journalctl(1), journald.conf(5), systemd.journal-fields(7),
   sd-journal(3), systemd-coredump(8), setfacl(1), sd_journal_print(4),
   pydoc systemd.journal

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