1SYSTEMD.JOURNAL-FIELDS(7) systemd.journal-fields SYSTEMD.JOURNAL-FIELDS(7)
2
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 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 a "http://",
90 "https://", "file:/", "man:" or "info:" URL.
91 TID=
93 The numeric thread ID (TID) the log message originates from.
94
96 Fields prefixed with an underscore are trusted fields, i.e. fields that
97 are implicitly added by the journal and cannot be altered by client
98 code.
99 _PID=, _UID=, _GID=
101 The process, user, and group ID of the process the journal entry
102 originates from formatted as a decimal string. Note that entries
103 obtained via "stdout" or "stderr" of forked processes will contain
104 credentials valid for a parent process (that initiated the
105 connection to systemd-journald).
106 _COMM=, _EXE=, _CMDLINE=
108 The name, the executable path, and the command line of the process
109 the journal entry originates from.
110 _CAP_EFFECTIVE=
112 The effective capabilities(7) of the process the journal entry
113 originates from.
114 _AUDIT_SESSION=, _AUDIT_LOGINUID=
116 The session and login UID of the process the journal entry
117 originates from, as maintained by the kernel audit subsystem.
118 _SYSTEMD_CGROUP=, _SYSTEMD_SLICE=, _SYSTEMD_UNIT=, _SYSTEMD_USER_UNIT=,
120 _SYSTEMD_USER_SLICE=, _SYSTEMD_SESSION=, _SYSTEMD_OWNER_UID=
121 The control group path in the systemd hierarchy, the systemd slice
122 unit name, the systemd unit name, the unit name in the systemd user
123 manager (if any), the systemd session ID (if any), and the owner
124 UID of the systemd user unit or systemd session (if any) of the
125 process the journal entry originates from.
126 _SELINUX_CONTEXT=
128 The SELinux security context (label) of the process the journal
129 entry originates from.
130 _SOURCE_REALTIME_TIMESTAMP=
132 The earliest trusted timestamp of the message, if any is known that
133 is different from the reception time of the journal. This is the
134 time in microseconds since the epoch UTC, formatted as a decimal
135 string.
136 _BOOT_ID=
138 The kernel boot ID for the boot the message was generated in,
139 formatted as a 128-bit hexadecimal string.
140 _MACHINE_ID=
142 The machine ID of the originating host, as available in machine-
143 id(5).
144 _SYSTEMD_INVOCATION_ID=
146 The invocation ID for the runtime cycle of the unit the message was
147 generated in, as available to processes of the unit in
148 $INVOCATION_ID (see systemd.exec(5)).
149 _HOSTNAME=
151 The name of the originating host.
152 _TRANSPORT=
154 How the entry was received by the journal service. Valid transports
155 are:
156 audit
158 for those read from the kernel audit subsystem
159 driver
161 for internally generated messages
162 syslog
164 for those received via the local syslog socket with the syslog
165 protocol
166 journal
168 for those received via the native journal protocol
169 stdout
171 for those read from a service's standard output or error output
172 kernel
174 for those read from the kernel
175 _STREAM_ID=
177 Only applies to "_TRANSPORT=stdout" records: specifies a randomized
178 128bit ID assigned to the stream connection when it was first
179 created. This ID is useful to reconstruct individual log streams
180 from the log records: all log records carrying the same stream ID
181 originate from the same stream.
182 _LINE_BREAK=
184 Only applies to "_TRANSPORT=stdout" records: indicates that the log
185 message in the standard output/error stream was not terminated with
186 a normal newline character ("\n", i.e. ASCII 10). Specifically,
187 when set this field is one of nul (in case the line was terminated
188 by a NUL byte), line-max (in case the maximum log line length was
189 reached, as configured with LineMax= in journald.conf(5)), eof (if
190 this was the last log record of a stream and the stream ended
191 without a final newline character), or pid-change (if the process
192 which generated the log output changed in the middle of a line).
193 Note that this record is not generated when a normal newline
194 character was used for marking the log line end.
195 _NAMESPACE=
197 If this file was written by a systemd-journald instance managing a
198 journal namespace that is not the default, this field contains the
199 namespace identifier. See systemd-journald.service(8) for details
200 about journal namespaces.
201
203 Kernel fields are fields that are used by messages originating in the
204 kernel and stored in the journal.
205 _KERNEL_DEVICE=
207 The kernel device name. If the entry is associated to a block
208 device, contains the major and minor numbers of the device node,
209 separated by ":" and prefixed by "b". Similarly for character
210 devices, but prefixed by "c". For network devices, this is the
211 interface index prefixed by "n". For all other devices, this is the
212 subsystem name prefixed by "+", followed by ":", followed by the
213 kernel device name.
214 _KERNEL_SUBSYSTEM=
216 The kernel subsystem name.
217 _UDEV_SYSNAME=
219 The kernel device name as it shows up in the device tree below
220 /sys/.
221 _UDEV_DEVNODE=
223 The device node path of this device in /dev/.
224 _UDEV_DEVLINK=
226 Additional symlink names pointing to the device node in /dev/. This
227 field is frequently set more than once per entry.
228
230 Fields in this section are used by programs to specify that they are
231 logging on behalf of another program or unit.
232 Fields used by the systemd-coredump coredump kernel helper:
234 COREDUMP_UNIT=, COREDUMP_USER_UNIT=
236 Used to annotate messages containing coredumps from system and
237 session units. See coredumpctl(1).
238 Privileged programs (currently UID 0) may attach OBJECT_PID= to a
240 message. This will instruct systemd-journald to attach additional
241 fields on behalf of the caller:
242 OBJECT_PID=PID
244 PID of the program that this message pertains to.
245 OBJECT_UID=, OBJECT_GID=, OBJECT_COMM=, OBJECT_EXE=, OBJECT_CMDLINE=,
247 OBJECT_AUDIT_SESSION=, OBJECT_AUDIT_LOGINUID=, OBJECT_SYSTEMD_CGROUP=,
248 OBJECT_SYSTEMD_SESSION=, OBJECT_SYSTEMD_OWNER_UID=,
249 OBJECT_SYSTEMD_UNIT=, OBJECT_SYSTEMD_USER_UNIT=
250 These are additional fields added automatically by
251 systemd-journald. Their meaning is the same as _UID=, _GID=,
252 _COMM=, _EXE=, _CMDLINE=, _AUDIT_SESSION=, _AUDIT_LOGINUID=,
253 _SYSTEMD_CGROUP=, _SYSTEMD_SESSION=, _SYSTEMD_UNIT=,
254 _SYSTEMD_USER_UNIT=, and _SYSTEMD_OWNER_UID= as described above,
255 except that the process identified by PID is described, instead of
256 the process which logged the message.
257
259 During serialization into external formats, such as the Journal Export
260 Format[1] or the Journal JSON Format[2], the addresses of journal
261 entries are serialized into fields prefixed with double underscores.
262 Note that these are not proper fields when stored in the journal but
263 for addressing metadata of entries. They cannot be written as part of
264 structured log entries via calls such as sd_journal_send(3). They may
265 also not be used as matches for sd_journal_add_match(3).
266 __CURSOR=
268 The cursor for the entry. A cursor is an opaque text string that
269 uniquely describes the position of an entry in the journal and is
270 portable across machines, platforms and journal files.
271 __REALTIME_TIMESTAMP=
273 The wallclock time (CLOCK_REALTIME) at the point in time the entry
274 was received by the journal, in microseconds since the epoch UTC,
275 formatted as a decimal string. This has different properties from
276 "_SOURCE_REALTIME_TIMESTAMP=", as it is usually a bit later but
277 more likely to be monotonic.
278 __MONOTONIC_TIMESTAMP=
280 The monotonic time (CLOCK_MONOTONIC) at the point in time the entry
281 was received by the journal in microseconds, formatted as a decimal
282 string. To be useful as an address for the entry, this should be
283 combined with the boot ID in "_BOOT_ID=".
284
286 systemd(1), systemd-journald.service(8), journalctl(1),
287 journald.conf(5), sd-journal(3), coredumpctl(1), systemd.directives(7)
288
290 1. Journal Export Format
291 https://www.freedesktop.org/wiki/Software/systemd/export
292 2. Journal JSON Format
294 https://www.freedesktop.org/wiki/Software/systemd/json
295systemd 248 SYSTEMD.JOURNAL-FIELDS(7)