systemd Developer Lennart Poettering lennart@poettering.net systemd-journald 8 systemd-journald.service systemd-journald systemd Journal Service systemd-journald.service /usr/lib/systemd/systemd-journald 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 syslog3 call, from STDOUT/STDERR of system services or via its native API. It will implicitly collect numerous meta data fields for each log messages in a secure and unfakeable way. See systemd.journal-fields7 for more information about the collected meta data. 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. systemd-journald will forward all received log messages to the AF_UNIX SOCK_DGRAM socket /run/systemd/journal/syslog (if it exists) which may be used by UNIX syslog daemons to process the data further. See journald.conf5 for information about the configuration of this service. SIGUSR1 Request that journal data from /run/ is flushed to /var/ in order to make it persistent (if this is enabled). This may be used after /var/ is mounted, but is generally not required since the first journal write when /var/ becomes writable triggers the flushing anyway. SIGUSR2 Request immediate rotation of the journal files. A few configuration parameters from journald.conf may be overriden on the kernel command line: systemd.journald.forward_to_syslog= systemd.journald.forward_to_kmsg= systemd.journald.forward_to_console= Enables/disables forwarding of collected log messages to syslog, the kernel log buffer or the system console. See journald.conf5 for information about these settings. systemd1, journalctl1, journald.conf5, systemd.journal-fields7