1SYSTEMD.JOURNAL-FIELDS(7) systemd.journal-fields SYSTEMD.JOURNAL-FIELDS(7)
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6 systemd.journal-fields - Special journal fields
7
9 Entries in the journal (as written by systemd-journald.service(8))
10 resemble a UNIX process environment block in syntax but with fields
11 that may include binary data. Primarily, fields are formatted UTF-8
12 text strings, and binary encoding is used only where formatting as
13 UTF-8 text strings makes little sense. New fields may freely be defined
14 by applications, but a few fields have special meanings. All fields
15 with special meanings are optional. In some cases, fields may appear
16 more than once per entry.
17
19 User fields are fields that are directly passed from clients and stored
20 in the journal.
21 MESSAGE=
23 The human-readable message string for this entry. This is supposed
24 to be the primary text shown to the user. It is usually not
25 translated (but might be in some cases), and is not supposed to be
26 parsed for metadata.
27 MESSAGE_ID=
29 A 128-bit message identifier ID for recognizing certain message
30 types, if this is desirable. This should contain a 128-bit ID
31 formatted as a lower-case hexadecimal string, without any
32 separating dashes or suchlike. This is recommended to be a
33 UUID-compatible ID, but this is not enforced, and formatted
34 differently. Developers can generate a new ID for this purpose with
35 systemd-id128 new.
36 PRIORITY=
38 A priority value between 0 ("emerg") and 7 ("debug") formatted as a
39 decimal string. This field is compatible with syslog's priority
40 concept.
41 CODE_FILE=, CODE_LINE=, CODE_FUNC=
43 The code location generating this message, if known. Contains the
44 source filename, the line number and the function name.
45 ERRNO=
47 The low-level Unix error number causing this entry, if any.
48 Contains the numeric value of errno(3) formatted as a decimal
49 string.
50 INVOCATION_ID=, USER_INVOCATION_ID=
52 A randomized, unique 128-bit ID identifying each runtime cycle of
53 the unit. This is different from _SYSTEMD_INVOCATION_ID in that it
54 is only used for messages coming from systemd code (e.g. logs from
55 the system/user manager or from forked processes performing
56 systemd-related setup).
57 SYSLOG_FACILITY=, SYSLOG_IDENTIFIER=, SYSLOG_PID=, SYSLOG_TIMESTAMP=
59 Syslog compatibility fields containing the facility (formatted as
60 decimal string), the identifier string (i.e. "tag"), the client
61 PID, and the timestamp as specified in the original datagram. (Note
62 that the tag is usually derived from glibc's
63 program_invocation_short_name variable, see
64 program_invocation_short_name(3).)
65 Note that the journal service does not validate the values of any
67 structured journal fields whose name is not prefixed with an
68 underscore, and this includes any syslog related fields such as
69 these. Hence, applications that supply a facility, PID, or log
70 level are expected to do so properly formatted, i.e. as numeric
71 integers formatted as decimal strings.
72 SYSLOG_RAW=
74 The original contents of the syslog line as received in the syslog
75 datagram. This field is only included if the MESSAGE= field was
76 modified compared to the original payload or the timestamp could
77 not be located properly and is not included in SYSLOG_TIMESTAMP=.
78 Message truncation occurs when when the message contains leading or
79 trailing whitespace (trailing and leading whitespace is stripped),
80 or it contains an embedded NUL byte (the NUL byte and anything
81 after it is not included). Thus, the original syslog line is either
82 stored as SYSLOG_RAW= or it can be recreated based on the stored
83 priority and facility, timestamp, identifier, and the message
84 payload in MESSAGE=.
85
87 Fields prefixed with an underscore are trusted fields, i.e. fields that
88 are implicitly added by the journal and cannot be altered by client
89 code.
90 _PID=, _UID=, _GID=
92 The process, user, and group ID of the process the journal entry
93 originates from formatted as a decimal string. Note that entries
94 obtained via "stdout" or "stderr" of forked processes will contain
95 credentials valid for a parent process (that initiated the
96 connection to systemd-journald).
97 _COMM=, _EXE=, _CMDLINE=
99 The name, the executable path, and the command line of the process
100 the journal entry originates from.
101 _CAP_EFFECTIVE=
103 The effective capabilities(7) of the process the journal entry
104 originates from.
105 _AUDIT_SESSION=, _AUDIT_LOGINUID=
107 The session and login UID of the process the journal entry
108 originates from, as maintained by the kernel audit subsystem.
109 _SYSTEMD_CGROUP=, _SYSTEMD_SLICE=, _SYSTEMD_UNIT=, _SYSTEMD_USER_UNIT=,
111 _SYSTEMD_USER_SLICE=, _SYSTEMD_SESSION=, _SYSTEMD_OWNER_UID=
112 The control group path in the systemd hierarchy, the the systemd
113 slice unit name, the systemd unit name, the unit name in the
114 systemd user manager (if any), the systemd session ID (if any), and
115 the owner UID of the systemd user unit or systemd session (if any)
116 of the process the journal entry originates from.
117 _SELINUX_CONTEXT=
119 The SELinux security context (label) of the process the journal
120 entry originates from.
121 _SOURCE_REALTIME_TIMESTAMP=
123 The earliest trusted timestamp of the message, if any is known that
124 is different from the reception time of the journal. This is the
125 time in microseconds since the epoch UTC, formatted as a decimal
126 string.
127 _BOOT_ID=
129 The kernel boot ID for the boot the message was generated in,
130 formatted as a 128-bit hexadecimal string.
131 _MACHINE_ID=
133 The machine ID of the originating host, as available in machine-
134 id(5).
135 _SYSTEMD_INVOCATION_ID=
137 The invocation ID for the runtime cycle of the unit the message was
138 generated in, as available to processes of the unit in
139 $INVOCATION_ID (see systemd.exec(5)).
140 _HOSTNAME=
142 The name of the originating host.
143 _TRANSPORT=
145 How the entry was received by the journal service. Valid transports
146 are:
147 audit
149 for those read from the kernel audit subsystem
150 driver
152 for internally generated messages
153 syslog
155 for those received via the local syslog socket with the syslog
156 protocol
157 journal
159 for those received via the native journal protocol
160 stdout
162 for those read from a service's standard output or error output
163 kernel
165 for those read from the kernel
166 _STREAM_ID=
168 Only applies to "_TRANSPORT=stdout" records: specifies a randomized
169 128bit ID assigned to the stream connection when it was first
170 created. This ID is useful to reconstruct individual log streams
171 from the log records: all log records carrying the same stream ID
172 originate from the same stream.
173 _LINE_BREAK=
175 Only applies to "_TRANSPORT=stdout" records: indicates that the log
176 message in the standard output/error stream was not terminated with
177 a normal newline character ("\n", i.e. ASCII 10). Specifically,
178 when set this field is one of nul (in case the line was terminated
179 by a NUL byte), line-max (in case the maximum log line length was
180 reached, as configured with LineMax= in journald.conf(5)) or eof
181 (if this was the last log record of a stream and the stream ended
182 without a final newline character). Note that this record is not
183 generated when a normal newline character was used for marking the
184 log line end.
185 _NAMESPACE=
187 If this file was written by a systemd-journald instance managing a
188 journal namespace that is not the default, this field contains the
189 namespace identifier. See systemd-journald.service(8) for details
190 about journal namespaces.
191
193 Kernel fields are fields that are used by messages originating in the
194 kernel and stored in the journal.
195 _KERNEL_DEVICE=
197 The kernel device name. If the entry is associated to a block
198 device, the major and minor of the device node, separated by ":"
199 and prefixed by "b". Similar for character devices but prefixed by
200 "c". For network devices, this is the interface index prefixed by
201 "n". For all other devices, this is the subsystem name prefixed by
202 "+", followed by ":", followed by the kernel device name.
203 _KERNEL_SUBSYSTEM=
205 The kernel subsystem name.
206 _UDEV_SYSNAME=
208 The kernel device name as it shows up in the device tree below
209 /sys.
210 _UDEV_DEVNODE=
212 The device node path of this device in /dev.
213 _UDEV_DEVLINK=
215 Additional symlink names pointing to the device node in /dev. This
216 field is frequently set more than once per entry.
217
219 Fields in this section are used by programs to specify that they are
220 logging on behalf of another program or unit.
221 Fields used by the systemd-coredump coredump kernel helper:
223 COREDUMP_UNIT=, COREDUMP_USER_UNIT=
225 Used to annotate messages containing coredumps from system and
226 session units. See coredumpctl(1).
227 Privileged programs (currently UID 0) may attach OBJECT_PID= to a
229 message. This will instruct systemd-journald to attach additional
230 fields on behalf of the caller:
231 OBJECT_PID=PID
233 PID of the program that this message pertains to.
234 OBJECT_UID=, OBJECT_GID=, OBJECT_COMM=, OBJECT_EXE=, OBJECT_CMDLINE=,
236 OBJECT_AUDIT_SESSION=, OBJECT_AUDIT_LOGINUID=, OBJECT_SYSTEMD_CGROUP=,
237 OBJECT_SYSTEMD_SESSION=, OBJECT_SYSTEMD_OWNER_UID=,
238 OBJECT_SYSTEMD_UNIT=, OBJECT_SYSTEMD_USER_UNIT=
239 These are additional fields added automatically by
240 systemd-journald. Their meaning is the same as _UID=, _GID=,
241 _COMM=, _EXE=, _CMDLINE=, _AUDIT_SESSION=, _AUDIT_LOGINUID=,
242 _SYSTEMD_CGROUP=, _SYSTEMD_SESSION=, _SYSTEMD_UNIT=,
243 _SYSTEMD_USER_UNIT=, and _SYSTEMD_OWNER_UID= as described above,
244 except that the process identified by PID is described, instead of
245 the process which logged the message.
246
248 During serialization into external formats, such as the Journal Export
249 Format[1] or the Journal JSON Format[2], the addresses of journal
250 entries are serialized into fields prefixed with double underscores.
251 Note that these are not proper fields when stored in the journal but
252 for addressing metadata of entries. They cannot be written as part of
253 structured log entries via calls such as sd_journal_send(3). They may
254 also not be used as matches for sd_journal_add_match(3)
255 __CURSOR=
257 The cursor for the entry. A cursor is an opaque text string that
258 uniquely describes the position of an entry in the journal and is
259 portable across machines, platforms and journal files.
260 __REALTIME_TIMESTAMP=
262 The wallclock time (CLOCK_REALTIME) at the point in time the entry
263 was received by the journal, in microseconds since the epoch UTC,
264 formatted as a decimal string. This has different properties from
265 "_SOURCE_REALTIME_TIMESTAMP=", as it is usually a bit later but
266 more likely to be monotonic.
267 __MONOTONIC_TIMESTAMP=
269 The monotonic time (CLOCK_MONOTONIC) at the point in time the entry
270 was received by the journal in microseconds, formatted as a decimal
271 string. To be useful as an address for the entry, this should be
272 combined with the boot ID in "_BOOT_ID=".
273
275 systemd(1), systemd-journald.service(8), journalctl(1),
276 journald.conf(5), sd-journal(3), coredumpctl(1), systemd.directives(7)
277
279 1. Journal Export Format
280 https://www.freedesktop.org/wiki/Software/systemd/export
281 2. Journal JSON Format
283 https://www.freedesktop.org/wiki/Software/systemd/json
284systemd 245 SYSTEMD.JOURNAL-FIELDS(7)