{
    "mode": "info",
    "parameter": "SYSTEMD-JOURNALD.SERVICE",
    "section": "",
    "url": "https://www.chedong.com/phpMan.php/info/SYSTEMD-JOURNALD.SERVICE/json",
    "generated": "2026-07-05T11:56:46Z",
    "synopsis": "systemd-journald.service\nsystemd-journald.socket\nsystemd-journald-dev-log.socket\nsystemd-journald-audit.socket\nsystemd-journald@.service\nsystemd-journald@.socket\nsystemd-journald-varlink@.socket\n/lib/systemd/systemd-journald",
    "sections": {
        "NAME": {
            "content": "systemd-journald.service, systemd-journald.socket, systemd-journald-\ndev-log.socket, systemd-journald-audit.socket, systemd-\njournald@.service, systemd-journald@.socket, systemd-journald-\nvarlink@.socket, systemd-journald - Journal service\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "systemd-journald.service\n\nsystemd-journald.socket\n\nsystemd-journald-dev-log.socket\n\nsystemd-journald-audit.socket\n\nsystemd-journald@.service\n\nsystemd-journald@.socket\n\nsystemd-journald-varlink@.socket\n\n/lib/systemd/systemd-journald\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "systemd-journald is a system service that collects and stores logging\ndata. It creates and maintains structured, indexed journals based on\nlogging information that is received from a variety of sources:\n\no   Kernel log messages, via kmsg\n\no   Simple system log messages, via the libc syslog(3) call\n\no   Structured system log messages via the native Journal API, see\nsdjournalprint(3) and Native Journal Protocol[1]\n\no   Standard output and standard error of service units. For further\ndetails see below.\n\no   Audit records, originating from the kernel audit subsystem\n\nThe daemon will implicitly collect numerous metadata fields for each\nlog messages in a secure and unfakeable way. See systemd.journal-\nfields(7) for more information about the collected metadata.\n\nLog data collected by the journal is primarily text-based but can also\ninclude binary data where necessary. Individual fields making up a log\nrecord stored in the journal may be up to 2^64-1 bytes in size.\n\nThe journal service stores log data either persistently below\n/var/log/journal or in a volatile way below /run/log/journal/ (in the\nlatter case it is lost at reboot). By default, log data is stored\npersistently if /var/log/journal/ exists during boot, with an implicit\nfallback to volatile storage otherwise. Use Storage= in\njournald.conf(5) to configure where log data is placed, independently\nof the existence of /var/log/journal/.\n\nNote that journald will initially use volatile storage, until a call to\njournalctl --flush (or sending SIGUSR1 to journald) will cause it to\nswitch to persistent logging (under the conditions mentioned above).\nThis is done automatically on boot via \"systemd-journal-flush.service\".\n\nOn systems where /var/log/journal/ does not exist yet but where\npersistent logging is desired (and the default journald.conf is used),\nit is sufficient to create the directory, and ensure it has the correct\naccess modes and ownership:\n\nmkdir -p /var/log/journal\nsystemd-tmpfiles --create --prefix /var/log/journal\n\nSee journald.conf(5) for information about the configuration of this\nservice.\n",
            "subsections": []
        },
        "STREAM LOGGING": {
            "content": "The systemd service manager invokes all service processes with standard\noutput and standard error connected to the journal by default. This\nbehaviour may be altered via the StandardOutput=/StandardError= unit\nfile settings, see systemd.exec(5) for details. The journal converts\nthe log byte stream received this way into individual log records,\nsplitting the stream at newline (\"\\n\", ASCII 10) and NUL bytes.\n\nIf systemd-journald.service is stopped, the stream connections\nassociated with all services are terminated. Further writes to those\nstreams by the service will result in EPIPE errors. In order to react\ngracefully in this case it is recommended that programs logging to\nstandard output/error ignore such errors. If the SIGPIPE UNIX signal\nhandler is not blocked or turned off, such write attempts will also\nresult in such process signals being generated, see signal(7). To\nmitigate this issue, systemd service manager explicitly turns off the\nSIGPIPE signal for all invoked processes by default (this may be\nchanged for each unit individually via the IgnoreSIGPIPE= option, see\nsystemd.exec(5) for details). After the standard output/standard error\nstreams have been terminated they may not be recovered until the\nservices they are associated with are restarted. Note that during\nnormal operation, systemd-journald.service stores copies of the file\ndescriptors for those streams in the service manager. If\nsystemd-journald.service is restarted using systemctl restart or\nequivalent operation instead of a pair of separate systemctl stop and\nsystemctl start commands (or equivalent operations), these stream\nconnections are not terminated and survive the restart. It is thus safe\nto restart systemd-journald.service, but stopping it is not\nrecommended.\n\nNote that the log record metadata for records transferred via such\nstandard output/error streams reflect the metadata of the peer the\nstream was originally created for. If the stream connection is passed\non to other processes (such as further child processes forked off the\nmain service process), the log records will not reflect their metadata,\nbut will continue to describe the original process. This is different\nfrom the other logging transports listed above, which are inherently\nrecord based and where the metadata is always associated with the\nindividual record.\n\nIn addition to the implicit standard output/error logging of services,\nstream logging is also available via the systemd-cat(1) command line\ntool.\n\nCurrently, the number of parallel log streams systemd-journald will\naccept is limited to 4096. When this limit is reached further log\nstreams may be established but will receive EPIPE right from the\nbeginning.\n",
            "subsections": []
        },
        "JOURNAL NAMESPACES": {
            "content": "Journal 'namespaces' are both a mechanism for logically isolating the\nlog stream of projects consisting of one or more services from the rest\nof the system and a mechanism for improving performance. Multiple\njournal namespaces may exist simultaneously, each defining its own,\nindependent log stream managed by its own instance of systemd-journald.\nNamespaces are independent of each other, both in the data store and in\nthe IPC interface. By default only a single 'default' namespace exists,\nmanaged by systemd-journald.service (and its associated socket units).\nAdditional namespaces are created by starting an instance of the\nsystemd-journald@.service service template. The instance name is the\nnamespace identifier, which is a short string used for referencing the\njournal namespace. Service units may be assigned to a specific journal\nnamespace through the LogNamespace= unit file setting, see\nsystemd.exec(5) for details. The --namespace= switch of journalctl(1)\nmay be used to view the log stream of a specific namespace. If the\nswitch is not used the log stream of the default namespace is shown,\ni.e. log data from other namespaces is not visible.\n\nServices associated with a specific log namespace may log via syslog,\nthe native logging protocol of the journal and via stdout/stderr; the\nlogging from all three transports is associated with the namespace.\n\nBy default only the default namespace will collect kernel and audit log\nmessages.\n\nThe systemd-journald instance of the default namespace is configured\nthrough /etc/systemd/journald.conf (see below), while the other\ninstances are configured through /etc/systemd/journald@NAMESPACE.conf.\nThe journal log data for the default namespace is placed in\n/var/log/journal/MACHINEID (see below) while the data for the other\nnamespaces is located in /var/log/journal/MACHINEID.NAMESPACE.\n",
            "subsections": []
        },
        "SIGNALS": {
            "content": "SIGUSR1\nRequest that journal data from /run/ is flushed to /var/ in order\nto make it persistent (if this is enabled). This must be used after\n/var/ is mounted, as otherwise log data from /run/ is never flushed\nto /var/ regardless of the configuration. Use the journalctl\n--flush command to request flushing of the journal files, and wait\nfor the operation to complete. See journalctl(1) for details.\n\nSIGUSR2\nRequest immediate rotation of the journal files. Use the journalctl\n--rotate command to request journal file rotation, and wait for the\noperation to complete.\n\nSIGRTMIN+1\nRequest that all unwritten log data is written to disk. Use the\njournalctl --sync command to trigger journal synchronization, and\nwait for the operation to complete.\n",
            "subsections": []
        },
        "KERNEL COMMAND LINE": {
            "content": "A few configuration parameters from journald.conf may be overridden on\nthe kernel command line:\n\nsystemd.journald.forwardtosyslog=, systemd.journald.forwardtokmsg=,\nsystemd.journald.forwardtoconsole=, systemd.journald.forwardtowall=\nEnables/disables forwarding of collected log messages to syslog,\nthe kernel log buffer, the system console or wall.\n\nSee journald.conf(5) for information about these settings.\n\nNote that these kernel command line options are only honoured by the\ndefault namespace, see above.\n",
            "subsections": []
        },
        "ACCESS CONTROL": {
            "content": "Journal files are, by default, owned and readable by the\n\"systemd-journal\" system group but are not writable. Adding a user to\nthis group thus enables them to read the journal files.\n\nBy default, each user, with a UID outside the range of system users,\ndynamic service users, and the nobody user, will get their own set of\njournal files in /var/log/journal/. See Users, Groups, UIDs and GIDs on\nsystemd systems[2] for more details about UID ranges. These journal\nfiles will not be owned by the user, however, in order to avoid that\nthe user can write to them directly. Instead, file system ACLs are used\nto ensure the user gets read access only.\n\nAdditional users and groups may be granted access to journal files via\nfile system access control lists (ACL). Distributions and\nadministrators may choose to grant read access to all members of the\n\"wheel\" and \"adm\" system groups with a command such as the following:\n\n# setfacl -Rnm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/\n\nNote that this command will update the ACLs both for existing journal\nfiles and for future journal files created in the /var/log/journal/\ndirectory.\n",
            "subsections": []
        },
        "FILES": {
            "content": "/etc/systemd/journald.conf\nConfigure systemd-journald behavior. See journald.conf(5).\n\n/run/log/journal/machine-id/*.journal,\n/run/log/journal/machine-id/*.journal~,\n/var/log/journal/machine-id/*.journal,\n/var/log/journal/machine-id/*.journal~\nsystemd-journald writes entries to files in\n/run/log/journal/machine-id/ or /var/log/journal/machine-id/ with\nthe \".journal\" suffix. If the daemon is stopped uncleanly, or if\nthe files are found to be corrupted, they are renamed using the\n\".journal~\" suffix, and systemd-journald starts writing to a new\nfile.  /run/ is used when /var/log/journal is not available, or\nwhen Storage=volatile is set in the journald.conf(5) configuration\nfile.\n\nWhen systemd-journald ceases writing to a journal file, it will be\nrenamed to \"original-name@suffix.journal\" (or\n\"original-name@suffix.journal~\"). Such files are \"archived\" and\nwill not be written to any more.\n\nIn general, it is safe to read or copy any journal file (active or\narchived).  journalctl(1) and the functions in the sd-journal(3)\nlibrary should be able to read all entries that have been fully\nwritten.\n\nsystemd-journald will automatically remove the oldest archived\njournal files to limit disk use. See SystemMaxUse= and related\nsettings in journald.conf(5).\n\n/dev/kmsg, /dev/log, /run/systemd/journal/dev-log,\n/run/systemd/journal/socket, /run/systemd/journal/stdout\nSockets and other file node paths that systemd-journald will listen\non and are visible in the file system. In addition to these,\nsystemd-journald can listen for audit events using netlink(7).\n\nIf journal namespacing is used these paths are slightly altered to\ninclude a namespace identifier, see above.\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "systemd(1), journalctl(1), journald.conf(5), systemd.journal-fields(7),\nsd-journal(3), systemd-coredump(8), setfacl(1), sdjournalprint(3),\npydoc systemd.journal\n",
            "subsections": []
        },
        "NOTES": {
            "content": "1. Native Journal Protocol\nhttps://systemd.io/JOURNALNATIVEPROTOCOL\n\n2. Users, Groups, UIDs and GIDs on systemd systems\nhttps://systemd.io/UIDS-GIDS\n\nsystemd 249                                        SYSTEMD-JOURNALD.SERVICE(8)",
            "subsections": []
        }
    },
    "summary": "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",
    "flags": [],
    "examples": [],
    "see_also": [
        {
            "name": "systemd",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/systemd/1/json"
        },
        {
            "name": "journalctl",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/journalctl/1/json"
        },
        {
            "name": "journald.conf",
            "section": "5",
            "url": "https://www.chedong.com/phpMan.php/man/journald.conf/5/json"
        },
        {
            "name": "systemd.journal-fields",
            "section": "7",
            "url": "https://www.chedong.com/phpMan.php/man/systemd.journal-fields/7/json"
        },
        {
            "name": "sd-journal",
            "section": "3",
            "url": "https://www.chedong.com/phpMan.php/man/sd-journal/3/json"
        },
        {
            "name": "systemd-coredump",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/systemd-coredump/8/json"
        },
        {
            "name": "setfacl",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/setfacl/1/json"
        },
        {
            "name": "sdjournalprint",
            "section": "3",
            "url": "https://www.chedong.com/phpMan.php/man/sdjournalprint/3/json"
        }
    ]
}