6       systemd-journald.service, systemd-journald.socket, systemd-journald-
7       dev-log.socket, systemd-journald-audit.socket, systemd-
8       journald@.service, systemd-journald@.socket, systemd-journald-
9       varlink@.socket, systemd-journald - Journal service


12       systemd-journald.service
14       systemd-journald.socket
16       systemd-journald-dev-log.socket
18       systemd-journald-audit.socket
20       systemd-journald@.service
22       systemd-journald@.socket
24       systemd-journald-varlink@.socket
26       /usr/lib/systemd/systemd-journald


29       systemd-journald is a system service that collects and stores logging
30       data. It creates and maintains structured, indexed journals based on
31       logging information that is received from a variety of sources:
33       ·   Kernel log messages, via kmsg
35       ·   Simple system log messages, via the libc syslog(3) call
37       ·   Structured system log messages via the native Journal API, see
38           sd_journal_print(3)
40       ·   Standard output and standard error of service units. For further
41           details see below.
43       ·   Audit records, originating from the kernel audit subsystem
45       The daemon will implicitly collect numerous metadata fields for each
46       log messages in a secure and unfakeable way. See systemd.journal-
47       fields(7) for more information about the collected metadata.
49       Log data collected by the journal is primarily text-based but can also
50       include binary data where necessary. Individual fields making up a log
51       record stored in the journal may be up to 2^64-1 bytes in size.
53       The journal service stores log data either persistently below
54       /var/log/journal or in a volatile way below /run/log/journal/ (in the
55       latter case it is lost at reboot). By default, log data is stored
56       persistently if /var/log/journal/ exists during boot, with an implicit
57       fallback to volatile storage otherwise. Use Storage= in
58       journald.conf(5) to configure where log data is placed, independently
59       of the existence of /var/log/journal/.
61       On systems where /var/log/journal/ does not exist yet but where
62       persistent logging is desired (and the default journald.conf is used),
63       it is sufficient to create the directory, and ensure it has the correct
64       access modes and ownership:
66           mkdir -p /var/log/journal
67           systemd-tmpfiles --create --prefix /var/log/journal
69       See journald.conf(5) for information about the configuration of this
70       service.


73       The systemd service manager invokes all service processes with standard
74       output and standard error connected to the journal by default. This
75       behaviour may be altered via the StandardOutput=/StandardError= unit
76       file settings, see systemd.exec(5) for details. The journal converts
77       the log byte stream received this way into individual log records,
78       splitting the stream at newline ("\n", ASCII 10) and NUL bytes.
80       If systemd-journald.service is stopped, the stream connections
81       associated with all services are terminated. Further writes to those
82       streams by the service will result in EPIPE errors. In order to react
83       gracefully in this case it is recommended that programs logging to
84       standard output/error ignore such errors. If the SIGPIPE UNIX signal
85       handler is not blocked or turned off, such write attempts will also
86       result in such process signals being generated, see signal(7). To
87       mitigate this issue, systemd service manager explicitly turns off the
88       SIGPIPE signal for all invoked processes by default (this may be
89       changed for each unit individually via the IgnoreSIGPIPE= option, see
90       systemd.exec(5) for details). After the standard output/standard error
91       streams have been terminated they may not be recovered until the
92       services they are associated with are restarted. Note that during
93       normal operation, systemd-journald.service stores copies of the file
94       descriptors for those streams in the service manager. If
95       systemd-journald.service is restarted using systemctl restart or
96       equivalent operation instead of a pair of separate systemctl stop and
97       systemctl start commands (or equivalent operations), these stream
98       connections are not terminated and survive the restart. It is thus safe
99       to restart systemd-journald.service, but stopping it is not
100       recommended.
102       Note that the log record metadata for records transferred via such
103       standard output/error streams reflect the metadata of the peer the
104       stream was originally created for. If the stream connection is passed
105       on to other processes (such as further child processes forked off the
106       main service process), the log records will not reflect their metadata,
107       but will continue to describe the original process. This is different
108       from the other logging transports listed above, which are inherently
109       record based and where the metadata is always associated with the
110       individual record.
112       In addition to the implicit standard output/error logging of services,
113       stream logging is also available via the systemd-cat(1) command line
114       tool.
116       Currently, the number of parallel log streams systemd-journald will
117       accept is limited to 4096. When this limit is reached further log
118       streams may be established but will receive EPIPE right from the
119       beginning.


122       Journal 'namespaces' are both a mechanism for logically isolating the
123       log stream of projects consisting of one or more services from the rest
124       of the system and a mechanism for improving performance. Multiple
125       journal namespaces may exist simultaneously, each defining its own,
126       independent log stream managed by its own instance of systemd-journald.
127       Namespaces are independent of each other, both in the data store and in
128       the IPC interface. By default only a single 'default' namespace exists,
129       managed by systemd-journald.service (and its associated socket units).
130       Additional namespaces are created by starting an instance of the
131       systemd-journald@.service service template. The instance name is the
132       namespace identifier, which is a short string used for referencing the
133       journal namespace. Service units may be assigned to a specific journal
134       namespace through the LogNamespace= unit file setting, see
135       systemd.exec(5) for details. The --namespace= switch of journalctl(1)
136       may be used to view the log stream of a specific namespace. If the
137       switch is not used the log stream of the default namespace is shown,
138       i.e. log data from other namespaces is not visible.
140       Services associated with a specific log namespace may log via syslog,
141       the native logging protocol of the journal and via stdout/stderr; the
142       logging from all three transports is associated with the namespace.
144       By default only the default namespace will collect kernel and audit log
145       messages.
147       The systemd-journald instance of the default namespace is configured
148       through /etc/systemd/journald.conf (see below), while the other
149       instances are configured through /etc/systemd/journald@NAMESPACE.conf.
150       The journal log data for the default namespace is placed in
151       /var/log/journal/MACHINE_ID (see below) while the data for the other
152       namespaces is located in /var/log/journal/MACHINE_ID.NAMESPACE.


155       SIGUSR1
156           Request that journal data from /run/ is flushed to /var/ in order
157           to make it persistent (if this is enabled). This must be used after
158           /var/ is mounted, as otherwise log data from /run is never flushed
159           to /var regardless of the configuration. Use the journalctl --flush
160           command to request flushing of the journal files, and wait for the
161           operation to complete. See journalctl(1) for details.
163       SIGUSR2
164           Request immediate rotation of the journal files. Use the journalctl
165           --rotate command to request journal file rotation, and wait for the
166           operation to complete.
168       SIGRTMIN+1
169           Request that all unwritten log data is written to disk. Use the
170           journalctl --sync command to trigger journal synchronization, and
171           wait for the operation to complete.


174       A few configuration parameters from journald.conf may be overridden on
175       the kernel command line:
177       systemd.journald.forward_to_syslog=, systemd.journald.forward_to_kmsg=,
178       systemd.journald.forward_to_console=, systemd.journald.forward_to_wall=
179           Enables/disables forwarding of collected log messages to syslog,
180           the kernel log buffer, the system console or wall.
182           See journald.conf(5) for information about these settings.
184       Note that these kernel command line options are only honoured by the
185       default namespace, see above.


188       Journal files are, by default, owned and readable by the
189       "systemd-journal" system group but are not writable. Adding a user to
190       this group thus enables them to read the journal files.
192       By default, each user, with a UID outside the range of system users,
193       dynamic service users, and the nobody user, will get their own set of
194       journal files in /var/log/journal/. See Users, Groups, UIDs and GIDs on
195       systemd systems[1] for more details about UID ranges. These journal
196       files will not be owned by the user, however, in order to avoid that
197       the user can write to them directly. Instead, file system ACLs are used
198       to ensure the user gets read access only.
200       Additional users and groups may be granted access to journal files via
201       file system access control lists (ACL). Distributions and
202       administrators may choose to grant read access to all members of the
203       "wheel" and "adm" system groups with a command such as the following:
205           # setfacl -Rnm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/
207       Note that this command will update the ACLs both for existing journal
208       files and for future journal files created in the /var/log/journal/
209       directory.


212       /etc/systemd/journald.conf
213           Configure systemd-journald behavior. See journald.conf(5).
215       /run/log/journal/machine-id/*.journal,
216       /run/log/journal/machine-id/*.journal~,
217       /var/log/journal/machine-id/*.journal,
218       /var/log/journal/machine-id/*.journal~
219           systemd-journald writes entries to files in
220           /run/log/journal/machine-id/ or /var/log/journal/machine-id/ with
221           the ".journal" suffix. If the daemon is stopped uncleanly, or if
222           the files are found to be corrupted, they are renamed using the
223           ".journal~" suffix, and systemd-journald starts writing to a new
224           file.  /run is used when /var/log/journal is not available, or when
225           Storage=volatile is set in the journald.conf(5) configuration file.
227           When systemd-journald ceases writing to a journal file, it will be
228           renamed to "original-name@suffix.journal" (or
229           "original-name@suffix.journal~"). Such files are "archived" and
230           will not be written to any more.
232           In general, it is safe to read or copy any journal file (active or
233           archived).  journalctl(1) and the functions in the sd-journal(3)
234           library should be able to read all entries that have been fully
235           written.
237           systemd-journald will automatically remove the oldest archived
238           journal files to limit disk use. See SystemMaxUse= and related
239           settings in journald.conf(5).
241       /dev/kmsg, /dev/log, /run/systemd/journal/dev-log,
242       /run/systemd/journal/socket, /run/systemd/journal/stdout
243           Sockets and other file node paths that systemd-journald will listen
244           on and are visible in the file system. In addition to these,
245           systemd-journald can listen for audit events using netlink(7).
247       If journal namespacing is used these paths are slightly altered to
248       include a namespace identifier, see above.


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


256        1. Users, Groups, UIDs and GIDs on systemd systems
257           https://systemd.io/UIDS-GIDS
261systemd 246                                        SYSTEMD-JOURNALD.SERVICE(8)