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
93 Fields prefixed with an underscore are trusted fields, i.e. fields that
94 are implicitly added by the journal and cannot be altered by client
95 code.
96 _PID=, _UID=, _GID=
98 The process, user, and group ID of the process the journal entry
99 originates from formatted as a decimal string. Note that entries
100 obtained via "stdout" or "stderr" of forked processes will contain
101 credentials valid for a parent process (that initiated the
102 connection to systemd-journald).
103 _COMM=, _EXE=, _CMDLINE=
105 The name, the executable path, and the command line of the process
106 the journal entry originates from.
107 _CAP_EFFECTIVE=
109 The effective capabilities(7) of the process the journal entry
110 originates from.
111 _AUDIT_SESSION=, _AUDIT_LOGINUID=
113 The session and login UID of the process the journal entry
114 originates from, as maintained by the kernel audit subsystem.
115 _SYSTEMD_CGROUP=, _SYSTEMD_SLICE=, _SYSTEMD_UNIT=, _SYSTEMD_USER_UNIT=,
117 _SYSTEMD_USER_SLICE=, _SYSTEMD_SESSION=, _SYSTEMD_OWNER_UID=
118 The control group path in the systemd hierarchy, the the systemd
119 slice unit name, the systemd unit name, the unit name in the
120 systemd user manager (if any), the systemd session ID (if any), and
121 the owner UID of the systemd user unit or systemd session (if any)
122 of the process the journal entry originates from.
123 _SELINUX_CONTEXT=
125 The SELinux security context (label) of the process the journal
126 entry originates from.
127 _SOURCE_REALTIME_TIMESTAMP=
129 The earliest trusted timestamp of the message, if any is known that
130 is different from the reception time of the journal. This is the
131 time in microseconds since the epoch UTC, formatted as a decimal
132 string.
133 _BOOT_ID=
135 The kernel boot ID for the boot the message was generated in,
136 formatted as a 128-bit hexadecimal string.
137 _MACHINE_ID=
139 The machine ID of the originating host, as available in machine-
140 id(5).
141 _SYSTEMD_INVOCATION_ID=
143 The invocation ID for the runtime cycle of the unit the message was
144 generated in, as available to processes of the unit in
145 $INVOCATION_ID (see systemd.exec(5)).
146 _HOSTNAME=
148 The name of the originating host.
149 _TRANSPORT=
151 How the entry was received by the journal service. Valid transports
152 are:
153 audit
155 for those read from the kernel audit subsystem
156 driver
158 for internally generated messages
159 syslog
161 for those received via the local syslog socket with the syslog
162 protocol
163 journal
165 for those received via the native journal protocol
166 stdout
168 for those read from a service's standard output or error output
169 kernel
171 for those read from the kernel
172 _STREAM_ID=
174 Only applies to "_TRANSPORT=stdout" records: specifies a randomized
175 128bit ID assigned to the stream connection when it was first
176 created. This ID is useful to reconstruct individual log streams
177 from the log records: all log records carrying the same stream ID
178 originate from the same stream.
179 _LINE_BREAK=
181 Only applies to "_TRANSPORT=stdout" records: indicates that the log
182 message in the standard output/error stream was not terminated with
183 a normal newline character ("\n", i.e. ASCII 10). Specifically,
184 when set this field is one of nul (in case the line was terminated
185 by a NUL byte), line-max (in case the maximum log line length was
186 reached, as configured with LineMax= in journald.conf(5)), eof (if
187 this was the last log record of a stream and the stream ended
188 without a final newline character), or pid-change (if the process
189 which generated the log output changed in the middle of a line).
190 Note that this record is not generated when a normal newline
191 character was used for marking the log line end.
192 _NAMESPACE=
194 If this file was written by a systemd-journald instance managing a
195 journal namespace that is not the default, this field contains the
196 namespace identifier. See systemd-journald.service(8) for details
197 about journal namespaces.
198
200 Kernel fields are fields that are used by messages originating in the
201 kernel and stored in the journal.
202 _KERNEL_DEVICE=
204 The kernel device name. If the entry is associated to a block
205 device, the major and minor of the device node, separated by ":"
206 and prefixed by "b". Similar for character devices but prefixed by
207 "c". For network devices, this is the interface index prefixed by
208 "n". For all other devices, this is the subsystem name prefixed by
209 "+", followed by ":", followed by the kernel device name.
210 _KERNEL_SUBSYSTEM=
212 The kernel subsystem name.
213 _UDEV_SYSNAME=
215 The kernel device name as it shows up in the device tree below
216 /sys.
217 _UDEV_DEVNODE=
219 The device node path of this device in /dev.
220 _UDEV_DEVLINK=
222 Additional symlink names pointing to the device node in /dev. This
223 field is frequently set more than once per entry.
224
226 Fields in this section are used by programs to specify that they are
227 logging on behalf of another program or unit.
228 Fields used by the systemd-coredump coredump kernel helper:
230 COREDUMP_UNIT=, COREDUMP_USER_UNIT=
232 Used to annotate messages containing coredumps from system and
233 session units. See coredumpctl(1).
234 Privileged programs (currently UID 0) may attach OBJECT_PID= to a
236 message. This will instruct systemd-journald to attach additional
237 fields on behalf of the caller:
238 OBJECT_PID=PID
240 PID of the program that this message pertains to.
241 OBJECT_UID=, OBJECT_GID=, OBJECT_COMM=, OBJECT_EXE=, OBJECT_CMDLINE=,
243 OBJECT_AUDIT_SESSION=, OBJECT_AUDIT_LOGINUID=, OBJECT_SYSTEMD_CGROUP=,
244 OBJECT_SYSTEMD_SESSION=, OBJECT_SYSTEMD_OWNER_UID=,
245 OBJECT_SYSTEMD_UNIT=, OBJECT_SYSTEMD_USER_UNIT=
246 These are additional fields added automatically by
247 systemd-journald. Their meaning is the same as _UID=, _GID=,
248 _COMM=, _EXE=, _CMDLINE=, _AUDIT_SESSION=, _AUDIT_LOGINUID=,
249 _SYSTEMD_CGROUP=, _SYSTEMD_SESSION=, _SYSTEMD_UNIT=,
250 _SYSTEMD_USER_UNIT=, and _SYSTEMD_OWNER_UID= as described above,
251 except that the process identified by PID is described, instead of
252 the process which logged the message.
253
255 During serialization into external formats, such as the Journal Export
256 Format[1] or the Journal JSON Format[2], the addresses of journal
257 entries are serialized into fields prefixed with double underscores.
258 Note that these are not proper fields when stored in the journal but
259 for addressing metadata of entries. They cannot be written as part of
260 structured log entries via calls such as sd_journal_send(3). They may
261 also not be used as matches for sd_journal_add_match(3).
262 __CURSOR=
264 The cursor for the entry. A cursor is an opaque text string that
265 uniquely describes the position of an entry in the journal and is
266 portable across machines, platforms and journal files.
267 __REALTIME_TIMESTAMP=
269 The wallclock time (CLOCK_REALTIME) at the point in time the entry
270 was received by the journal, in microseconds since the epoch UTC,
271 formatted as a decimal string. This has different properties from
272 "_SOURCE_REALTIME_TIMESTAMP=", as it is usually a bit later but
273 more likely to be monotonic.
274 __MONOTONIC_TIMESTAMP=
276 The monotonic time (CLOCK_MONOTONIC) at the point in time the entry
277 was received by the journal in microseconds, formatted as a decimal
278 string. To be useful as an address for the entry, this should be
279 combined with the boot ID in "_BOOT_ID=".
280
282 systemd(1), systemd-journald.service(8), journalctl(1),
283 journald.conf(5), sd-journal(3), coredumpctl(1), systemd.directives(7)
284
286 1. Journal Export Format
287 https://www.freedesktop.org/wiki/Software/systemd/export
288 2. Journal JSON Format
290 https://www.freedesktop.org/wiki/Software/systemd/json
291systemd 246 SYSTEMD.JOURNAL-FIELDS(7)