man/journalctl.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2012 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
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  18   Lesser General Public License for more details.
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  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
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  23
  24 <refentry id="journalctl">
  25
  26         <refentryinfo>
  27                 <title>journalctl</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>journalctl</refentrytitle>
  42                 <manvolnum>1</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>journalctl</refname>
  47                 <refpurpose>Query the systemd journal</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <cmdsynopsis>
  52                         <command>journalctl</command>
  53                         <arg choice="opt" rep="repeat">OPTIONS</arg>
  54                         <arg choice="opt" rep="repeat">MATCHES</arg>
  55                 </cmdsynopsis>
  56         </refsynopsisdiv>
  57
  58         <refsect1>
  59                 <title>Description</title>
  60
  61                 <para><command>journalctl</command> may be used to
  62                 query the contents of the
  63                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  64                 journal as written by
  65                 <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
  66
  67                 <para>If called without parameter it will show the full
  68                 contents of the journal, starting with the oldest
  69                 entry collected.</para>
  70
  71                 <para>If one or more match arguments are passed the
  72                 output is filtered accordingly. A match is in the
  73                 format <literal>FIELD=VALUE</literal>,
  74                 e.g. <literal>_SYSTEMD_UNIT=httpd.service</literal>,
  75                 referring to the components of a structured journal
  76                 entry. See
  77                 <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  78                 for a list of well-known fields. If multiple matches
  79                 are specified matching different fields the log
  80                 entries are filtered by both, i.e. the resulting output
  81                 will show only entries matching all the specified
  82                 matches of this kind. If two matches apply to the same
  83                 field, then they are automatically matched as
  84                 alternatives, i.e. the resulting output will show
  85                 entries matching any of the specified matches for the
  86                 same field. Finally, if the character
  87                 "<literal>+</literal>" appears as separate word on the
  88                 command line all matches before and after are combined
  89                 in a disjunction (i.e. logical OR).</para>
  90
  91                 <para>As shortcuts for a few types of field/value
  92                 matches file paths may be specified. If a file path
  93                 refers to an executable file, this is equivalent to an
  94                 <literal>_EXE=</literal> match for the canonicalized
  95                 binary path. Similar, if a path refers to a device
  96                 node, this is equivalent to a
  97                 <literal>_KERNEL_DEVICE=</literal> match for the
  98                 device.</para>
  99
 100                 <para>Output is interleaved from all accessible
 101                 journal files, whether they are rotated or currently
 102                 being written, and regardless whether they belong to the
 103                 system itself or are accessible user journals.</para>
 104
 105                 <para>All users are granted access to their private
 106                 per-user journals. However, by default only root and
 107                 users who are members of the <literal>adm</literal>
 108                 group get access to the system journal and the
 109                 journals of other users.</para>
 110         </refsect1>
 111
 112         <refsect1>
 113                 <title>Options</title>
 114
 115                 <para>The following options are understood:</para>
 116
 117                 <variablelist>
 118                         <varlistentry>
 119                                 <term><option>-h</option></term>
 120                                 <term><option>--help</option></term>
 121
 122                                 <listitem><para>Prints a short help
 123                                 text and exits.</para></listitem>
 124                         </varlistentry>
 125
 126                         <varlistentry>
 127                                 <term><option>--version</option></term>
 128
 129                                 <listitem><para>Prints a short version
 130                                 string and exits.</para></listitem>
 131                         </varlistentry>
 132
 133                         <varlistentry>
 134                                 <term><option>--no-pager</option></term>
 135
 136                                 <listitem><para>Do not pipe output into a
 137                                 pager.</para></listitem>
 138                         </varlistentry>
 139
 140                         <varlistentry>
 141                                 <term><option>-l</option></term>
 142                                 <term><option>--full</option></term>
 143
 144                                 <listitem><para>Show all (printable) fields in
 145                                 full.</para></listitem>
 146                         </varlistentry>
 147
 148                         <varlistentry>
 149                                 <term><option>-a</option></term>
 150                                 <term><option>--all</option></term>
 151
 152                                 <listitem><para>Show all fields in
 153                                 full, even if they include unprintable
 154                                 characters or are very
 155                                 long.</para></listitem>
 156                         </varlistentry>
 157
 158                         <varlistentry>
 159                                 <term><option>-f</option></term>
 160                                 <term><option>--follow</option></term>
 161
 162                                 <listitem><para>Show only the most recent
 163                                 journal entries, and continuously print
 164                                 new entries as they are appended to
 165                                 the journal.</para></listitem>
 166                         </varlistentry>
 167
 168                         <varlistentry>
 169                                 <term><option>-e</option></term>
 170                                 <term><option>--pager-end</option></term>
 171
 172                                 <listitem><para>Immediately jump to
 173                                 the end of the journal inside the
 174                                 implied pager tool. This implies
 175                                 <option>-n1000</option> to guarantee
 176                                 that the pager won't buffer logs of
 177                                 unbounded size. This may be overridden
 178                                 with an explicit <option>-n</option>
 179                                 with some other numeric value on the
 180                                 command line. Note that this option is
 181                                 only supported for the
 182                                 <citerefentry><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 183                                 pager.</para></listitem>
 184                         </varlistentry>
 185
 186                         <varlistentry>
 187                                 <term><option>-n</option></term>
 188                                 <term><option>--lines=</option></term>
 189
 190                                 <listitem><para>Show the most recent
 191                                 journal events and limit the number of
 192                                 events shown. If
 193                                 <option>--follow</option> is used,
 194                                 this option is implied. The argument,
 195                                 a positive integer, is optional, and
 196                                 defaults to 10. </para></listitem>
 197                         </varlistentry>
 198
 199                         <varlistentry>
 200                                 <term><option>--no-tail</option></term>
 201
 202                                 <listitem><para>Show all stored output
 203                                 lines, even in follow mode. Undoes the
 204                                 effect of
 205                                 <option>--lines=</option>.</para></listitem>
 206                         </varlistentry>
 207
 208                         <varlistentry>
 209                                 <term><option>-r</option></term>
 210                                 <term><option>--reverse</option></term>
 211
 212                                 <listitem><para>Reverse output, so the newest
 213                                 entries are displayed first.</para></listitem>
 214                         </varlistentry>
 215
 216                         <varlistentry>
 217                                 <term><option>-o</option></term>
 218                                 <term><option>--output=</option></term>
 219
 220                                 <listitem><para>Controls the
 221                                 formatting of the journal entries that
 222                                 are shown. Takes one of
 223                                 <literal>short</literal>,
 224                                 <literal>short-monotonic</literal>,
 225                                 <literal>verbose</literal>,
 226                                 <literal>export</literal>,
 227                                 <literal>json</literal>,
 228                                 <literal>json-pretty</literal>,
 229                                 <literal>json-sse</literal>,
 230                                 <literal>cat</literal>. <literal>short</literal>
 231                                 is the default and generates an output
 232                                 that is mostly identical to the
 233                                 formatting of classic syslog log
 234                                 files, showing one line per journal
 235                                 entry. <literal>short-monotonic</literal>
 236                                 is very similar but shows monotonic
 237                                 timestamps instead of wallclock
 238                                 timestamps. <literal>verbose</literal>
 239                                 shows the full structured entry items
 240                                 with all
 241                                 fields. <literal>export</literal>
 242                                 serializes the journal into a binary
 243                                 (but mostly text-based) stream
 244                                 suitable for backups and network
 245                                 transfer (see <ulink
 246                                 url="http://www.freedesktop.org/wiki/Software/systemd/export">Journal
 247                                 Export Format</ulink> for more
 248                                 information). <literal>json</literal>
 249                                 formats entries as JSON data
 250                                 structures, one per
 251                                 line (see <ulink
 252                                 url="http://www.freedesktop.org/wiki/Software/systemd/json">Journal
 253                                 JSON Format</ulink> for more
 254                                 information). <literal>json-pretty</literal>
 255                                 also formats entries as JSON data
 256                                 structures, but formats them in
 257                                 multiple lines in order to make them
 258                                 more readable for
 259                                 humans. <literal>json-sse</literal>
 260                                 also formats entries as JSON data
 261                                 structures, but wraps them in a format
 262                                 suitable for <ulink
 263                                 url="https://developer.mozilla.org/en-US/docs/Server-sent_events/Using_server-sent_events">Server-Sent
 264                                 Events</ulink>. <literal>cat</literal>
 265                                 generates a very terse output only
 266                                 showing the actual message of each
 267                                 journal entry with no meta data, not
 268                                 even a timestamp.</para></listitem>
 269                         </varlistentry>
 270
 271                         <varlistentry>
 272                                 <term><option>-x</option></term>
 273                                 <term><option>--catalog</option></term>
 274
 275                                 <listitem><para>Augment log lines with
 276                                 explanation texts from the message
 277                                 catalog. This will add explanatory
 278                                 help texts to log messages in the
 279                                 output where this is available. These
 280                                 short help texts will explain the
 281                                 context of an error or log event,
 282                                 possible solutions, as well as
 283                                 pointers to support forums, developer
 284                                 documentation and any other relevant
 285                                 manuals. Note that help texts are not
 286                                 available for all messages, but only
 287                                 for selected ones. For more
 288                                 information on the message catalog
 289                                 please refer to the <ulink
 290                                 url="http://www.freedesktop.org/wiki/Software/systemd/catalog">Message
 291                                 Catalog Developer
 292                                 Documentation</ulink>.</para></listitem>
 293                         </varlistentry>
 294
 295                         <varlistentry>
 296                                 <term><option>-q</option></term>
 297                                 <term><option>--quiet</option></term>
 298
 299                                 <listitem><para>Suppresses any warning
 300                                 message regarding inaccessible system
 301                                 journals when run as normal
 302                                 user.</para></listitem>
 303                         </varlistentry>
 304
 305                         <varlistentry>
 306                                 <term><option>-m</option></term>
 307                                 <term><option>--merge</option></term>
 308
 309                                 <listitem><para>Show entries
 310                                 interleaved from all available
 311                                 journals, including remote
 312                                 ones.</para></listitem>
 313                         </varlistentry>
 314
 315                         <varlistentry>
 316                                 <term><option>-b</option></term>
 317                                 <term><option>--this-boot</option></term>
 318
 319                                 <listitem><para>Show data only from
 320                                 current boot. This will add a match
 321                                 for <literal>_BOOT_ID=</literal> for
 322                                 the current boot ID of the
 323                                 kernel.</para></listitem>
 324                         </varlistentry>
 325
 326                         <varlistentry>
 327                                 <term><option>-k</option></term>
 328                                 <term><option>--dmesg</option></term>
 329
 330                                 <listitem><para>Show kernel messages from
 331                                 current boot. This implies <option>-b</option>
 332                                 and adds the match <literal>_TRANSPORT=kernel</literal>.
 333                                 </para></listitem>
 334                         </varlistentry>
 335
 336                         <varlistentry>
 337                                 <term><option>-u</option></term>
 338                                 <term><option>--unit=</option></term>
 339
 340                                 <listitem><para>Show messages for the
 341                                 specified systemd unit. This will add
 342                                 a match for messages from the unit
 343                                 (<literal>_SYSTEMD_UNIT=</literal>)
 344                                 and additional matches for messages
 345                                 from systemd and messages about
 346                                 coredumps for the specified unit.</para>
 347                                 <para>This parameter can be specified multiple times.
 348                                 </para></listitem>
 349                         </varlistentry>
 350
 351                         <varlistentry>
 352                                 <term><option>--user-unit=</option></term>
 353
 354                                 <listitem><para>Show messages for the
 355                                 specified user session unit. This will
 356                                 add a match for messages from the unit
 357                                 (<literal>_SYSTEMD_USER_UNIT=</literal>
 358                                 and <literal>_UID=</literal>) and
 359                                 additional matches for messages from
 360                                 session systemd and messages about
 361                                 coredumps for the specified unit.</para>
 362                                 <para>This parameter can be specified multiple times.
 363                                 </para></listitem>
 364                         </varlistentry>
 365
 366                         <varlistentry>
 367                                 <term><option>-p</option></term>
 368                                 <term><option>--priority=</option></term>
 369
 370                                 <listitem><para>Filter output by
 371                                 message priorities or priority
 372                                 ranges. Takes either a single numeric
 373                                 or textual log level (i.e. between
 374                                 0/<literal>emerg</literal> and
 375                                 7/<literal>debug</literal>), or a
 376                                 range of numeric/text log levels in
 377                                 the form FROM..TO. The log levels are
 378                                 the usual syslog log levels as
 379                                 documented in
 380                                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 381                                 i.e. <literal>emerg</literal> (0),
 382                                 <literal>alert</literal> (1),
 383                                 <literal>crit</literal> (2),
 384                                 <literal>err</literal> (3),
 385                                 <literal>warning</literal> (4),
 386                                 <literal>notice</literal> (5),
 387                                 <literal>info</literal> (6),
 388                                 <literal>debug</literal> (7). If a
 389                                 single log level is specified all
 390                                 messages with this log level or a
 391                                 lower (hence more important) log level
 392                                 are shown. If a range is specified all
 393                                 messages within the range are shown,
 394                                 including both the start and the end
 395                                 value of the range. This will add
 396                                 <literal>PRIORITY=</literal> matches
 397                                 for the specified
 398                                 priorities.</para></listitem>
 399                         </varlistentry>
 400
 401                         <varlistentry>
 402                                 <term><option>-c</option></term>
 403                                 <term><option>--cursor=</option></term>
 404
 405                                 <listitem><para>Start showing entries
 406                                 from the location in the journal
 407                                 specified by the passed
 408                                 cursor.</para></listitem>
 409                         </varlistentry>
 410
 411                         <varlistentry>
 412                                 <term><option>--since=</option></term>
 413                                 <term><option>--until=</option></term>
 414
 415                                 <listitem><para>Start showing entries
 416                                 on or newer than the specified date,
 417                                 or on or older than the specified
 418                                 date, respectively. Date specifications should be of
 419                                 the format "2012-10-30 18:17:16". If
 420                                 the time part is omitted, 00:00:00 is
 421                                 assumed. If only the seconds component
 422                                 is omitted, :00 is assumed. If the
 423                                 date component is omitted, the
 424                                 current day is assumed. Alternatively
 425                                 the strings
 426                                 <literal>yesterday</literal>,
 427                                 <literal>today</literal>,
 428                                 <literal>tomorrow</literal> are
 429                                 understood, which refer to 00:00:00 of
 430                                 the day before the current day, the
 431                                 current day, or the day after the
 432                                 current day, respectively. <literal>now</literal>
 433                                 refers to the current time. Finally,
 434                                 relative times may be specified,
 435                                 prefixed with <literal>-</literal> or
 436                                 <literal>+</literal>, referring to
 437                                 times before or after the current
 438                                 time, respectively.</para></listitem>
 439                         </varlistentry>
 440
 441                         <varlistentry>
 442                                 <term><option>-F</option></term>
 443                                 <term><option>--field=</option></term>
 444
 445                                 <listitem><para>Print all possible
 446                                 data values the specified field can
 447                                 take in all entries of the
 448                                 journal.</para></listitem>
 449                         </varlistentry>
 450
 451                         <varlistentry>
 452                                 <term><option>--system</option></term>
 453                                 <term><option>--user</option></term>
 454
 455                                 <listitem><para>Show messages from
 456                                 system services and the kernel (with
 457                                 <option>--system</option>).  Show
 458                                 messages from service of current user
 459                                 (with <option>--user</option>).
 460                                 If neither is specified, show all
 461                                 messages that the user can see.
 462                                 </para></listitem>
 463                         </varlistentry>
 464
 465                         <varlistentry>
 466                                 <term><option>-D <replaceable>DIR</replaceable></option></term>
 467                                 <term><option>--directory=<replaceable>DIR</replaceable></option></term>
 468
 469                                 <listitem><para>Takes a directory path
 470                                 as argument. If specified journalctl
 471                                 will operate on the specified journal
 472                                 directory
 473                                 <replaceable>DIR</replaceable> instead
 474                                 of the default runtime and system
 475                                 journal paths.</para></listitem>
 476                         </varlistentry>
 477
 478                         <varlistentry>
 479                                 <term><option>--file=<replaceable>GLOB</replaceable></option></term>
 480
 481                                 <listitem><para>Takes a file glob as
 482                                 argument. If specified journalctl will
 483                                 operate on the specified journal files
 484                                 matching <replaceable>GLOB</replaceable>
 485                                 instead of the default runtime and
 486                                 system journal paths. May be specified
 487                                 multiple times, in which case files will
 488                                 be suitably interleaved.</para></listitem>
 489                         </varlistentry>
 490
 491                         <varlistentry>
 492                                 <term><option>--root=<replaceable>ROOT</replaceable></option></term>
 493
 494                                 <listitem><para>Takes a directory path
 495                                 as argument. If specified journalctl
 496                                 will operate on catalog file hierarchy
 497                                 underneath the specified directory
 498                                 instead of the root directory
 499                                 (e.g. <option>--update-catalog</option>
 500                                 will create
 501                                 <filename><replaceable>ROOT</replaceable>/var/lib/systemd/catalog/database</filename>).
 502                                 </para></listitem>
 503                         </varlistentry>
 504
 505                         <varlistentry>
 506                                 <term><option>--new-id128</option></term>
 507
 508                                 <listitem><para>Instead of showing
 509                                 journal contents generate a new 128
 510                                 bit ID suitable for identifying
 511                                 messages. This is intended for usage
 512                                 by developers who need a new
 513                                 identifier for a new message they
 514                                 introduce and want to make
 515                                 recognizable. Will print the new ID in
 516                                 three different formats which can be
 517                                 copied into source code or
 518                                 similar.</para></listitem>
 519                         </varlistentry>
 520
 521                         <varlistentry>
 522                                 <term><option>--header</option></term>
 523
 524                                 <listitem><para>Instead of showing
 525                                 journal contents show internal header
 526                                 information of the journal fields
 527                                 accessed.</para></listitem>
 528                         </varlistentry>
 529
 530                         <varlistentry>
 531                                 <term><option>--disk-usage</option></term>
 532
 533                                 <listitem><para>Shows the current disk
 534                                 usage of all
 535                                 journal files.</para></listitem>
 536                         </varlistentry>
 537
 538                         <varlistentry>
 539                                 <term><option>--list-catalog
 540                                 <optional><replaceable>ID128...</replaceable></optional>
 541                                 </option></term>
 542
 543                                 <listitem><para>List the contents of
 544                                 the message catalog, as table of
 545                                 message IDs plus their short
 546                                 description strings.</para>
 547
 548                                 <para>If any
 549                                 <replaceable>ID128</replaceable>s are
 550                                 specified, only those entries are shown.
 551                                 </para>
 552                                 </listitem>
 553                         </varlistentry>
 554
 555                         <varlistentry>
 556                                 <term><option>--dump-catalog
 557                                 <optional><replaceable>ID128...</replaceable></optional>
 558                                 </option></term>
 559
 560                                 <listitem><para>Show the contents of
 561                                 the message catalog, with entries
 562                                 separated by a line consisting of two
 563                                 dashes and the id (the format is the
 564                                 same as <filename>.catalog</filename>
 565                                 files.</para>
 566
 567                                 <para>If any
 568                                 <replaceable>ID128</replaceable>s are
 569                                 specified, only those entries are shown.
 570                                 </para>
 571                                 </listitem>
 572                         </varlistentry>
 573
 574                         <varlistentry>
 575                                 <term><option>--update-catalog</option></term>
 576
 577                                 <listitem><para>Update the message
 578                                 catalog index. This command needs to
 579                                 be executed each time new catalog
 580                                 files are installed, removed or
 581                                 updated to rebuild the binary catalog
 582                                 index.</para></listitem>
 583                         </varlistentry>
 584
 585                         <varlistentry>
 586                                 <term><option>--setup-keys</option></term>
 587
 588                                 <listitem><para>Instead of showing
 589                                 journal contents generate a new key
 590                                 pair for Forward Secure Sealing
 591                                 (FSS). This will generate a sealing
 592                                 key and a verification key. The
 593                                 sealing key is stored in the journal
 594                                 data directory and shall remain on the
 595                                 host. The verification key should be
 596                                 stored externally. Also see the
 597                                 <option>Seal=</option> option in
 598                                 <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 599                                 for details.</para></listitem>
 600                         </varlistentry>
 601
 602                         <varlistentry>
 603                                 <term><option>--interval=</option></term>
 604
 605                                 <listitem><para>Specifies the change
 606                                 interval for the sealing key, when
 607                                 generating an FSS key pair with
 608                                 <option>--setup-keys</option>. Shorter
 609                                 intervals increase CPU consumption but
 610                                 shorten the time range of
 611                                 undetectable journal
 612                                 alterations. Defaults to
 613                                 15min.</para></listitem>
 614                         </varlistentry>
 615
 616                         <varlistentry>
 617                                 <term><option>--verify</option></term>
 618
 619                                 <listitem><para>Check the journal file
 620                                 for internal consistency. If the
 621                                 file has been generated with FSS
 622                                 enabled, and the FSS verification key
 623                                 has been specified with
 624                                 <option>--verify-key=</option>
 625                                 authenticity of the journal file is
 626                                 verified.</para></listitem>
 627                         </varlistentry>
 628
 629                         <varlistentry>
 630                                 <term><option>--verify-key=</option></term>
 631
 632                                 <listitem><para>Specifies the FSS
 633                                 verification key to use for the
 634                                 <option>--verify</option>
 635                                 operation.</para></listitem>
 636                         </varlistentry>
 637
 638                 </variablelist>
 639         </refsect1>
 640
 641         <refsect1>
 642                 <title>Exit status</title>
 643
 644                 <para>On success 0 is returned, a non-zero failure
 645                 code otherwise.</para>
 646         </refsect1>
 647
 648         <refsect1>
 649                 <title>Environment</title>
 650
 651                 <variablelist class='environment-variables'>
 652                         <varlistentry>
 653                                 <term><varname>$SYSTEMD_PAGER</varname></term>
 654                                 <listitem><para>Pager to use when
 655                                 <option>--no-pager</option> is not given;
 656                                 overrides <varname>$PAGER</varname>.  Setting
 657                                 this to an empty string or the value
 658                                 <literal>cat</literal> is equivalent to passing
 659                                 <option>--no-pager</option>.</para></listitem>
 660                         </varlistentry>
 661                 </variablelist>
 662         </refsect1>
 663
 664         <refsect1>
 665                 <title>Examples</title>
 666
 667                 <para>Without arguments all collected logs are shown
 668                 unfiltered:</para>
 669
 670                 <programlisting>journalctl</programlisting>
 671
 672                 <para>With one match specified all entries with a field matching the expression are shown:</para>
 673
 674                 <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service</programlisting>
 675
 676                 <para>If two different fields are matched only entries matching both expressions at the same time are shown:</para>
 677
 678                 <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=28097</programlisting>
 679
 680                 <para>If two matches refer to the same field all entries matching either expression are shown:</para>
 681
 682                 <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _SYSTEMD_UNIT=dbus.service</programlisting>
 683
 684                 <para>If the separator "<literal>+</literal>" is used
 685                 two expressions may be combined in a logical OR. The
 686                 following will show all messages from the Avahi
 687                 service process with the PID 28097 plus all messages
 688                 from the D-Bus service (from any of its
 689                 processes):</para>
 690
 691                 <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=28097 + _SYSTEMD_UNIT=dbus.service</programlisting>
 692
 693                 <para>Show all logs generated by the D-Bus executable:</para>
 694
 695                 <programlisting>journalctl /usr/bin/dbus-daemon</programlisting>
 696
 697                 <para>Show all logs of the kernel device node <filename noindex='true'>/dev/sda</filename>:</para>
 698
 699                 <programlisting>journalctl /dev/sda</programlisting>
 700
 701         </refsect1>
 702
 703         <refsect1>
 704                 <title>See Also</title>
 705                 <para>
 706                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 707                         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 708                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 709                         <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 710                         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 711                 </para>
 712         </refsect1>
 713
 714 </refentry>