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 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 DOCUMENTATION=
87 A documentation URL with further information about the topic of the
88 log message. Tools such as journalctl will include a hyperlink to
89 an URL specified this way in their output. Should be an "http://",
90 "https://", "file:/", "man:" or "info:" URL.
91 TID=
93 The numeric thread ID (TID) the log message originates from.
94 UNIT=, USER_UNIT=
96 The name of a unit. Used by the system and user managers when
97 logging about specific units.
98 When --unit=name or --user-unit=name are used with journalctl(1), a
100 match pattern that includes "UNIT=name.service" or
101 "USER_UNIT=name.service" will be generated.
102
104 Fields prefixed with an underscore are trusted fields, i.e. fields that
105 are implicitly added by the journal and cannot be altered by client
106 code.
107 _PID=, _UID=, _GID=
109 The process, user, and group ID of the process the journal entry
110 originates from formatted as a decimal string. Note that entries
111 obtained via "stdout" or "stderr" of forked processes will contain
112 credentials valid for a parent process (that initiated the
113 connection to systemd-journald).
114 _COMM=, _EXE=, _CMDLINE=
116 The name, the executable path, and the command line of the process
117 the journal entry originates from.
118 _CAP_EFFECTIVE=
120 The effective capabilities(7) of the process the journal entry
121 originates from.
122 _AUDIT_SESSION=, _AUDIT_LOGINUID=
124 The session and login UID of the process the journal entry
125 originates from, as maintained by the kernel audit subsystem.
126 _SYSTEMD_CGROUP=, _SYSTEMD_SLICE=, _SYSTEMD_UNIT=, _SYSTEMD_USER_UNIT=,
128 _SYSTEMD_USER_SLICE=, _SYSTEMD_SESSION=, _SYSTEMD_OWNER_UID=
129 The control group path in the systemd hierarchy, the systemd slice
130 unit name, the systemd unit name, the unit name in the systemd user
131 manager (if any), the systemd session ID (if any), and the owner
132 UID of the systemd user unit or systemd session (if any) of the
133 process the journal entry originates from.
134 _SELINUX_CONTEXT=
136 The SELinux security context (label) of the process the journal
137 entry originates from.
138 _SOURCE_REALTIME_TIMESTAMP=
140 The earliest trusted timestamp of the message, if any is known that
141 is different from the reception time of the journal. This is the
142 time in microseconds since the epoch UTC, formatted as a decimal
143 string.
144 _BOOT_ID=
146 The kernel boot ID for the boot the message was generated in,
147 formatted as a 128-bit hexadecimal string.
148 _MACHINE_ID=
150 The machine ID of the originating host, as available in machine-
151 id(5).
152 _SYSTEMD_INVOCATION_ID=
154 The invocation ID for the runtime cycle of the unit the message was
155 generated in, as available to processes of the unit in
156 $INVOCATION_ID (see systemd.exec(5)).
157 _HOSTNAME=
159 The name of the originating host.
160 _TRANSPORT=
162 How the entry was received by the journal service. Valid transports
163 are:
164 audit
166 for those read from the kernel audit subsystem
167 driver
169 for internally generated messages
170 syslog
172 for those received via the local syslog socket with the syslog
173 protocol
174 journal
176 for those received via the native journal protocol
177 stdout
179 for those read from a service's standard output or error output
180 kernel
182 for those read from the kernel
183 _STREAM_ID=
185 Only applies to "_TRANSPORT=stdout" records: specifies a randomized
186 128bit ID assigned to the stream connection when it was first
187 created. This ID is useful to reconstruct individual log streams
188 from the log records: all log records carrying the same stream ID
189 originate from the same stream.
190 _LINE_BREAK=
192 Only applies to "_TRANSPORT=stdout" records: indicates that the log
193 message in the standard output/error stream was not terminated with
194 a normal newline character ("\n", i.e. ASCII 10). Specifically,
195 when set this field is one of nul (in case the line was terminated
196 by a NUL byte), line-max (in case the maximum log line length was
197 reached, as configured with LineMax= in journald.conf(5)), eof (if
198 this was the last log record of a stream and the stream ended
199 without a final newline character), or pid-change (if the process
200 which generated the log output changed in the middle of a line).
201 Note that this record is not generated when a normal newline
202 character was used for marking the log line end.
203 _NAMESPACE=
205 If this file was written by a systemd-journald instance managing a
206 journal namespace that is not the default, this field contains the
207 namespace identifier. See systemd-journald.service(8) for details
208 about journal namespaces.
209
211 Kernel fields are fields that are used by messages originating in the
212 kernel and stored in the journal.
213 _KERNEL_DEVICE=
215 The kernel device name. If the entry is associated to a block
216 device, contains the major and minor numbers of the device node,
217 separated by ":" and prefixed by "b". Similarly for character
218 devices, but prefixed by "c". For network devices, this is the
219 interface index prefixed by "n". For all other devices, this is the
220 subsystem name prefixed by "+", followed by ":", followed by the
221 kernel device name.
222 _KERNEL_SUBSYSTEM=
224 The kernel subsystem name.
225 _UDEV_SYSNAME=
227 The kernel device name as it shows up in the device tree below
228 /sys/.
229 _UDEV_DEVNODE=
231 The device node path of this device in /dev/.
232 _UDEV_DEVLINK=
234 Additional symlink names pointing to the device node in /dev/. This
235 field is frequently set more than once per entry.
236
238 Fields in this section are used by programs to specify that they are
239 logging on behalf of another program or unit.
240 Fields used by the systemd-coredump coredump kernel helper:
242 COREDUMP_UNIT=, COREDUMP_USER_UNIT=
244 Used to annotate messages containing coredumps from system and
245 session units. See coredumpctl(1).
246 Privileged programs (currently UID 0) may attach OBJECT_PID= to a
248 message. This will instruct systemd-journald to attach additional
249 fields on behalf of the caller:
250 OBJECT_PID=PID
252 PID of the program that this message pertains to.
253 OBJECT_UID=, OBJECT_GID=, OBJECT_COMM=, OBJECT_EXE=, OBJECT_CMDLINE=,
255 OBJECT_AUDIT_SESSION=, OBJECT_AUDIT_LOGINUID=, OBJECT_SYSTEMD_CGROUP=,
256 OBJECT_SYSTEMD_SESSION=, OBJECT_SYSTEMD_OWNER_UID=,
257 OBJECT_SYSTEMD_UNIT=, OBJECT_SYSTEMD_USER_UNIT=
258 These are additional fields added automatically by
259 systemd-journald. Their meaning is the same as _UID=, _GID=,
260 _COMM=, _EXE=, _CMDLINE=, _AUDIT_SESSION=, _AUDIT_LOGINUID=,
261 _SYSTEMD_CGROUP=, _SYSTEMD_SESSION=, _SYSTEMD_UNIT=,
262 _SYSTEMD_USER_UNIT=, and _SYSTEMD_OWNER_UID= as described above,
263 except that the process identified by PID is described, instead of
264 the process which logged the message.
265
267 During serialization into external formats, such as the Journal Export
268 Format[1] or the Journal JSON Format[2], the addresses of journal
269 entries are serialized into fields prefixed with double underscores.
270 Note that these are not proper fields when stored in the journal but
271 for addressing metadata of entries. They cannot be written as part of
272 structured log entries via calls such as sd_journal_send(3). They may
273 also not be used as matches for sd_journal_add_match(3).
274 __CURSOR=
276 The cursor for the entry. A cursor is an opaque text string that
277 uniquely describes the position of an entry in the journal and is
278 portable across machines, platforms and journal files.
279 __REALTIME_TIMESTAMP=
281 The wallclock time (CLOCK_REALTIME) at the point in time the entry
282 was received by the journal, in microseconds since the epoch UTC,
283 formatted as a decimal string. This has different properties from
284 "_SOURCE_REALTIME_TIMESTAMP=", as it is usually a bit later but
285 more likely to be monotonic.
286 __MONOTONIC_TIMESTAMP=
288 The monotonic time (CLOCK_MONOTONIC) at the point in time the entry
289 was received by the journal in microseconds, formatted as a decimal
290 string. To be useful as an address for the entry, this should be
291 combined with the boot ID in "_BOOT_ID=".
292
294 systemd(1), systemd-journald.service(8), journalctl(1),
295 journald.conf(5), sd-journal(3), coredumpctl(1), systemd.directives(7)
296
298 1. Journal Export Format
299 https://systemd.io/JOURNAL_EXPORT_FORMATS#journal-export-format
300 2. Journal JSON Format
302 https://systemd.io/JOURNAL_EXPORT_FORMATS#journal-json-format
303systemd 251 SYSTEMD.JOURNAL-FIELDS(7)