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 resemble an environment block in their syntax
10 but with fields that can include binary data. Primarily, fields are
11 formatted UTF-8 text strings, and binary formatting is used only where
12 formatting as UTF-8 text strings makes little sense. New fields may
13 freely be defined by applications, but a few fields have special
14 meaning. All fields with special meanings are optional. In some cases,
15 fields may appear more than once per entry.
16
18 User fields are fields that are directly passed from clients and stored
19 in the journal.
20 MESSAGE=
22 The human-readable message string for this entry. This is supposed
23 to be the primary text shown to the user. It is usually not
24 translated (but might be in some cases), and is not supposed to be
25 parsed for metadata.
26 MESSAGE_ID=
28 A 128-bit message identifier ID for recognizing certain message
29 types, if this is desirable. This should contain a 128-bit ID
30 formatted as a lower-case hexadecimal string, without any
31 separating dashes or suchlike. This is recommended to be a
32 UUID-compatible ID, but this is not enforced, and formatted
33 differently. Developers can generate a new ID for this purpose with
34 systemd-id128 new.
35 PRIORITY=
37 A priority value between 0 ("emerg") and 7 ("debug") formatted as a
38 decimal string. This field is compatible with syslog's priority
39 concept.
40 CODE_FILE=, CODE_LINE=, CODE_FUNC=
42 The code location generating this message, if known. Contains the
43 source filename, the line number and the function name.
44 ERRNO=
46 The low-level Unix error number causing this entry, if any.
47 Contains the numeric value of errno(3) formatted as a decimal
48 string.
49 SYSLOG_FACILITY=, SYSLOG_IDENTIFIER=, SYSLOG_PID=, SYSLOG_TIMESTAMP=
51 Syslog compatibility fields containing the facility (formatted as
52 decimal string), the identifier string (i.e. "tag"), the client
53 PID, and the timestamp as specified in the original datagram. (Note
54 that the tag is usually derived from glibc's
55 program_invocation_short_name variable, see
56 program_invocation_short_name(3).)
57 Note that the journal service does not validate the values of any
59 structured journal fields whose name is not prefixed with an
60 underscore, and this includes any syslog related fields such as
61 these. Hence, applications that supply a facility, PID, or log
62 level are expected to do so properly formatted, i.e. as numeric
63 integers formatted as decimal strings.
64 SYSLOG_RAW=
66 The original contents of the syslog line as received in the syslog
67 datagram. This field is only included if the MESSAGE= field was
68 modified compared to the original payload or the timestamp could
69 not be located properly and is not included in SYSLOG_TIMESTAMP=.
70 Message truncation occurs when when the message contains leading or
71 trailing whitespace (trailing and leading whitespace is stripped),
72 or it contains an embedded NUL byte (the NUL byte and anything
73 after it is not included). Thus, the original syslog line is either
74 stored as SYSLOG_RAW= or it can be recreated based on the stored
75 priority and facility, timestamp, identifier, and the message
76 payload in MESSAGE=.
77
79 Fields prefixed with an underscore are trusted fields, i.e. fields that
80 are implicitly added by the journal and cannot be altered by client
81 code.
82 _PID=, _UID=, _GID=
84 The process, user, and group ID of the process the journal entry
85 originates from formatted as a decimal string. Note that entries
86 obtained via "stdout" or "stderr" of forked processes will contain
87 credentials valid for a parent process (that initiated the
88 connection to systemd-journald).
89 _COMM=, _EXE=, _CMDLINE=
91 The name, the executable path, and the command line of the process
92 the journal entry originates from.
93 _CAP_EFFECTIVE=
95 The effective capabilities(7) of the process the journal entry
96 originates from.
97 _AUDIT_SESSION=, _AUDIT_LOGINUID=
99 The session and login UID of the process the journal entry
100 originates from, as maintained by the kernel audit subsystem.
101 _SYSTEMD_CGROUP=, _SYSTEMD_SLICE=, _SYSTEMD_UNIT=, _SYSTEMD_USER_UNIT=,
103 _SYSTEMD_USER_SLICE=, _SYSTEMD_SESSION=, _SYSTEMD_OWNER_UID=
104 The control group path in the systemd hierarchy, the the systemd
105 slice unit name, the systemd unit name, the unit name in the
106 systemd user manager (if any), the systemd session ID (if any), and
107 the owner UID of the systemd user unit or systemd session (if any)
108 of the process the journal entry originates from.
109 _SELINUX_CONTEXT=
111 The SELinux security context (label) of the process the journal
112 entry originates from.
113 _SOURCE_REALTIME_TIMESTAMP=
115 The earliest trusted timestamp of the message, if any is known that
116 is different from the reception time of the journal. This is the
117 time in microseconds since the epoch UTC, formatted as a decimal
118 string.
119 _BOOT_ID=
121 The kernel boot ID for the boot the message was generated in,
122 formatted as a 128-bit hexadecimal string.
123 _MACHINE_ID=
125 The machine ID of the originating host, as available in machine-
126 id(5).
127 _SYSTEMD_INVOCATION_ID=
129 The invocation ID for the runtime cycle of the unit the message was
130 generated in, as available to processes of the unit in
131 $INVOCATION_ID (see systemd.exec(5)).
132 _HOSTNAME=
134 The name of the originating host.
135 _TRANSPORT=
137 How the entry was received by the journal service. Valid transports
138 are:
139 audit
141 for those read from the kernel audit subsystem
142 driver
144 for internally generated messages
145 syslog
147 for those received via the local syslog socket with the syslog
148 protocol
149 journal
151 for those received via the native journal protocol
152 stdout
154 for those read from a service's standard output or error output
155 kernel
157 for those read from the kernel
158 _STREAM_ID=
160 Only applies to "_TRANSPORT=stdout" records: specifies a randomized
161 128bit ID assigned to the stream connection when it was first
162 created. This ID is useful to reconstruct individual log streams
163 from the log records: all log records carrying the same stream ID
164 originate from the same stream.
165 _LINE_BREAK=
167 Only applies to "_TRANSPORT=stdout" records: indicates that the log
168 message in the standard output/error stream was not terminated with
169 a normal newline character ("\n", i.e. ASCII 10). Specifically,
170 when set this field is one of nul (in case the line was terminated
171 by a NUL byte), line-max (in case the maximum log line length was
172 reached, as configured with LineMax= in journald.conf(5)) or eof
173 (if this was the last log record of a stream and the stream ended
174 without a final newline character). Note that this record is not
175 generated when a normal newline character was used for marking the
176 log line end.
177
179 Kernel fields are fields that are used by messages originating in the
180 kernel and stored in the journal.
181 _KERNEL_DEVICE=
183 The kernel device name. If the entry is associated to a block
184 device, the major and minor of the device node, separated by ":"
185 and prefixed by "b". Similar for character devices but prefixed by
186 "c". For network devices, this is the interface index prefixed by
187 "n". For all other devices, this is the subsystem name prefixed by
188 "+", followed by ":", followed by the kernel device name.
189 _KERNEL_SUBSYSTEM=
191 The kernel subsystem name.
192 _UDEV_SYSNAME=
194 The kernel device name as it shows up in the device tree below
195 /sys.
196 _UDEV_DEVNODE=
198 The device node path of this device in /dev.
199 _UDEV_DEVLINK=
201 Additional symlink names pointing to the device node in /dev. This
202 field is frequently set more than once per entry.
203
205 Fields in this section are used by programs to specify that they are
206 logging on behalf of another program or unit.
207 Fields used by the systemd-coredump coredump kernel helper:
209 COREDUMP_UNIT=, COREDUMP_USER_UNIT=
211 Used to annotate messages containing coredumps from system and
212 session units. See coredumpctl(1).
213 Privileged programs (currently UID 0) may attach OBJECT_PID= to a
215 message. This will instruct systemd-journald to attach additional
216 fields on behalf of the caller:
217 OBJECT_PID=PID
219 PID of the program that this message pertains to.
220 OBJECT_UID=, OBJECT_GID=, OBJECT_COMM=, OBJECT_EXE=, OBJECT_CMDLINE=,
222 OBJECT_AUDIT_SESSION=, OBJECT_AUDIT_LOGINUID=, OBJECT_SYSTEMD_CGROUP=,
223 OBJECT_SYSTEMD_SESSION=, OBJECT_SYSTEMD_OWNER_UID=,
224 OBJECT_SYSTEMD_UNIT=, OBJECT_SYSTEMD_USER_UNIT=
225 These are additional fields added automatically by
226 systemd-journald. Their meaning is the same as _UID=, _GID=,
227 _COMM=, _EXE=, _CMDLINE=, _AUDIT_SESSION=, _AUDIT_LOGINUID=,
228 _SYSTEMD_CGROUP=, _SYSTEMD_SESSION=, _SYSTEMD_UNIT=,
229 _SYSTEMD_USER_UNIT=, and _SYSTEMD_OWNER_UID= as described above,
230 except that the process identified by PID is described, instead of
231 the process which logged the message.
232
234 During serialization into external formats, such as the Journal Export
235 Format[1] or the Journal JSON Format[2], the addresses of journal
236 entries are serialized into fields prefixed with double underscores.
237 Note that these are not proper fields when stored in the journal but
238 for addressing metadata of entries. They cannot be written as part of
239 structured log entries via calls such as sd_journal_send(3). They may
240 also not be used as matches for sd_journal_add_match(3)
241 __CURSOR=
243 The cursor for the entry. A cursor is an opaque text string that
244 uniquely describes the position of an entry in the journal and is
245 portable across machines, platforms and journal files.
246 __REALTIME_TIMESTAMP=
248 The wallclock time (CLOCK_REALTIME) at the point in time the entry
249 was received by the journal, in microseconds since the epoch UTC,
250 formatted as a decimal string. This has different properties from
251 "_SOURCE_REALTIME_TIMESTAMP=", as it is usually a bit later but
252 more likely to be monotonic.
253 __MONOTONIC_TIMESTAMP=
255 The monotonic time (CLOCK_MONOTONIC) at the point in time the entry
256 was received by the journal in microseconds, formatted as a decimal
257 string. To be useful as an address for the entry, this should be
258 combined with the boot ID in "_BOOT_ID=".
259
261 systemd(1), journalctl(1), journald.conf(5), sd-journal(3),
262 coredumpctl(1), systemd.directives(7)
263
265 1. Journal Export Format
266 https://www.freedesktop.org/wiki/Software/systemd/export
267 2. Journal JSON Format
269 https://www.freedesktop.org/wiki/Software/systemd/json
270systemd 243 SYSTEMD.JOURNAL-FIELDS(7)