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
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   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.
  14
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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 parameters, 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. Similarly, 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 of 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
 111                 <para>The output is paged through
 112                 <command>less</command> by default, and long lines are
 113                 "truncated" to screen width. The hidden part can be
 114                 viewed by using the left-arrow and right-arrow
 115                 keys. Paging can be disabled, see
 116                 <option>--no-pager</option> and section Environment
 117                 below.</para>
 118
 119                 <para>When outputing to a tty, lines are colored
 120                 according to priority: lines of level ERROR and higher
 121                 are colored red, lines of level NOTICE and higher are
 122                 highlighted, and other lines are displayed normally.
 123                 </para>
 124         </refsect1>
 125
 126         <refsect1>
 127                 <title>Options</title>
 128
 129                 <para>The following options are understood:</para>
 130
 131                 <variablelist>
 132                         <varlistentry>
 133                                 <term><option>-h</option></term>
 134                                 <term><option>--help</option></term>
 135
 136                                 <listitem><para>Prints a short help
 137                                 text and exits.</para></listitem>
 138                         </varlistentry>
 139
 140                         <varlistentry>
 141                                 <term><option>--version</option></term>
 142
 143                                 <listitem><para>Prints a short version
 144                                 string and exits.</para></listitem>
 145                         </varlistentry>
 146
 147                         <varlistentry>
 148                                 <term><option>--no-pager</option></term>
 149
 150                                 <listitem><para>Do not pipe output into a
 151                                 pager.</para></listitem>
 152                         </varlistentry>
 153
 154                         <varlistentry>
 155                                 <term><option>-l</option></term>
 156                                 <term><option>--full</option></term>
 157
 158                                 <listitem><para>Show all (printable) fields in
 159                                 full.</para></listitem>
 160                         </varlistentry>
 161
 162                         <varlistentry>
 163                                 <term><option>-a</option></term>
 164                                 <term><option>--all</option></term>
 165
 166                                 <listitem><para>Show all fields in
 167                                 full, even if they include unprintable
 168                                 characters or are very
 169                                 long.</para></listitem>
 170                         </varlistentry>
 171
 172                         <varlistentry>
 173                                 <term><option>-f</option></term>
 174                                 <term><option>--follow</option></term>
 175
 176                                 <listitem><para>Show only the most recent
 177                                 journal entries, and continuously print
 178                                 new entries as they are appended to
 179                                 the journal.</para></listitem>
 180                         </varlistentry>
 181
 182                         <varlistentry>
 183                                 <term><option>-e</option></term>
 184                                 <term><option>--pager-end</option></term>
 185
 186                                 <listitem><para>Immediately jump to
 187                                 the end of the journal inside the
 188                                 implied pager tool. This implies
 189                                 <option>-n1000</option> to guarantee
 190                                 that the pager will not buffer logs of
 191                                 unbounded size. This may be overridden
 192                                 with an explicit <option>-n</option>
 193                                 with some other numeric value on the
 194                                 command line. Note that this option is
 195                                 only supported for the
 196                                 <citerefentry><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 197                                 pager.</para></listitem>
 198                         </varlistentry>
 199
 200                         <varlistentry>
 201                                 <term><option>-n</option></term>
 202                                 <term><option>--lines=</option></term>
 203
 204                                 <listitem><para>Show the most recent
 205                                 journal events and limit the number of
 206                                 events shown. If
 207                                 <option>--follow</option> is used,
 208                                 this option is implied. The argument,
 209                                 a positive integer, is optional, and
 210                                 defaults to 10. </para></listitem>
 211                         </varlistentry>
 212
 213                         <varlistentry>
 214                                 <term><option>--no-tail</option></term>
 215
 216                                 <listitem><para>Show all stored output
 217                                 lines, even in follow mode. Undoes the
 218                                 effect of
 219                                 <option>--lines=</option>.</para></listitem>
 220                         </varlistentry>
 221
 222                         <varlistentry>
 223                                 <term><option>-r</option></term>
 224                                 <term><option>--reverse</option></term>
 225
 226                                 <listitem><para>Reverse output, so the newest
 227                                 entries are displayed first.</para></listitem>
 228                         </varlistentry>
 229
 230                         <varlistentry>
 231                                 <term><option>-o</option></term>
 232                                 <term><option>--output=</option></term>
 233
 234                                 <listitem><para>Controls the
 235                                 formatting of the journal entries that
 236                                 are shown. Takes one of
 237                                 <literal>short</literal>,
 238                                 <literal>short-monotonic</literal>,
 239                                 <literal>verbose</literal>,
 240                                 <literal>export</literal>,
 241                                 <literal>json</literal>,
 242                                 <literal>json-pretty</literal>,
 243                                 <literal>json-sse</literal>,
 244                                 <literal>cat</literal>. <literal>short</literal>
 245                                 is the default and generates an output
 246                                 that is mostly identical to the
 247                                 formatting of classic syslog
 248                                 files, showing one line per journal
 249                                 entry. <literal>short-monotonic</literal>
 250                                 is very similar but shows monotonic
 251                                 timestamps instead of wallclock
 252                                 timestamps. <literal>verbose</literal>
 253                                 shows the full structured entry items
 254                                 with all
 255                                 fields. <literal>export</literal>
 256                                 serializes the journal into a binary
 257                                 (but mostly text-based) stream
 258                                 suitable for backups and network
 259                                 transfer (see <ulink
 260                                 url="http://www.freedesktop.org/wiki/Software/systemd/export">Journal
 261                                 Export Format</ulink> for more
 262                                 information). <literal>json</literal>
 263                                 formats entries as JSON data
 264                                 structures, one per
 265                                 line (see <ulink
 266                                 url="http://www.freedesktop.org/wiki/Software/systemd/json">Journal
 267                                 JSON Format</ulink> for more
 268                                 information). <literal>json-pretty</literal>
 269                                 also formats entries as JSON data
 270                                 structures, but formats them in
 271                                 multiple lines in order to make them
 272                                 more readable for
 273                                 humans. <literal>json-sse</literal>
 274                                 also formats entries as JSON data
 275                                 structures, but wraps them in a format
 276                                 suitable for <ulink
 277                                 url="https://developer.mozilla.org/en-US/docs/Server-sent_events/Using_server-sent_events">Server-Sent
 278                                 Events</ulink>. <literal>cat</literal>
 279                                 generates a very terse output only
 280                                 showing the actual message of each
 281                                 journal entry with no meta data, not
 282                                 even a timestamp.</para></listitem>
 283                         </varlistentry>
 284
 285                         <varlistentry>
 286                                 <term><option>-x</option></term>
 287                                 <term><option>--catalog</option></term>
 288
 289                                 <listitem><para>Augment log lines with
 290                                 explanation texts from the message
 291                                 catalog. This will add explanatory
 292                                 help texts to log messages in the
 293                                 output where this is available. These
 294                                 short help texts will explain the
 295                                 context of an error or log event,
 296                                 possible solutions, as well as
 297                                 pointers to support forums, developer
 298                                 documentation and any other relevant
 299                                 manuals. Note that help texts are not
 300                                 available for all messages, but only
 301                                 for selected ones. For more
 302                                 information on the message catalog,
 303                                 please refer to the <ulink
 304                                 url="http://www.freedesktop.org/wiki/Software/systemd/catalog">Message
 305                                 Catalog Developer
 306                                 Documentation</ulink>.</para></listitem>
 307                         </varlistentry>
 308
 309                         <varlistentry>
 310                                 <term><option>-q</option></term>
 311                                 <term><option>--quiet</option></term>
 312
 313                                 <listitem><para>Suppresses any warning
 314                                 message regarding inaccessible system
 315                                 journals when run as normal
 316                                 user.</para></listitem>
 317                         </varlistentry>
 318
 319                         <varlistentry>
 320                                 <term><option>-m</option></term>
 321                                 <term><option>--merge</option></term>
 322
 323                                 <listitem><para>Show entries
 324                                 interleaved from all available
 325                                 journals, including remote
 326                                 ones.</para></listitem>
 327                         </varlistentry>
 328
 329                         <varlistentry>
 330                                 <term><option>-b</option></term>
 331                                 <term><option>--this-boot</option></term>
 332
 333                                 <listitem><para>Show data only from
 334                                 current boot. This will add a match
 335                                 for <literal>_BOOT_ID=</literal> for
 336                                 the current boot ID of the
 337                                 kernel.</para></listitem>
 338                         </varlistentry>
 339
 340                         <varlistentry>
 341                                 <term><option>-k</option></term>
 342                                 <term><option>--dmesg</option></term>
 343
 344                                 <listitem><para>Show kernel messages from
 345                                 current boot. This implies <option>-b</option>
 346                                 and adds the match <literal>_TRANSPORT=kernel</literal>.
 347                                 </para></listitem>
 348                         </varlistentry>
 349
 350                         <varlistentry>
 351                                 <term><option>-u</option></term>
 352                                 <term><option>--unit=</option></term>
 353
 354                                 <listitem><para>Show messages for the
 355                                 specified systemd unit. This will add
 356                                 a match for messages from the unit
 357                                 (<literal>_SYSTEMD_UNIT=</literal>)
 358                                 and additional matches for messages
 359                                 from systemd and messages about
 360                                 coredumps for the specified unit.</para>
 361                                 <para>This parameter can be specified multiple times.
 362                                 </para></listitem>
 363                         </varlistentry>
 364
 365                         <varlistentry>
 366                                 <term><option>--user-unit=</option></term>
 367
 368                                 <listitem><para>Show messages for the
 369                                 specified user session unit. This will
 370                                 add a match for messages from the unit
 371                                 (<literal>_SYSTEMD_USER_UNIT=</literal>
 372                                 and <literal>_UID=</literal>) and
 373                                 additional matches for messages from
 374                                 session systemd and messages about
 375                                 coredumps for the specified unit.</para>
 376                                 <para>This parameter can be specified multiple times.
 377                                 </para></listitem>
 378                         </varlistentry>
 379
 380                         <varlistentry>
 381                                 <term><option>-p</option></term>
 382                                 <term><option>--priority=</option></term>
 383
 384                                 <listitem><para>Filter output by
 385                                 message priorities or priority
 386                                 ranges. Takes either a single numeric
 387                                 or textual log level (i.e. between
 388                                 0/<literal>emerg</literal> and
 389                                 7/<literal>debug</literal>), or a
 390                                 range of numeric/text log levels in
 391                                 the form FROM..TO. The log levels are
 392                                 the usual syslog log levels as
 393                                 documented in
 394                                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 395                                 i.e. <literal>emerg</literal> (0),
 396                                 <literal>alert</literal> (1),
 397                                 <literal>crit</literal> (2),
 398                                 <literal>err</literal> (3),
 399                                 <literal>warning</literal> (4),
 400                                 <literal>notice</literal> (5),
 401                                 <literal>info</literal> (6),
 402                                 <literal>debug</literal> (7). If a
 403                                 single log level is specified, all
 404                                 messages with this log level or a
 405                                 lower (hence more important) log level
 406                                 are shown. If a range is specified, all
 407                                 messages within the range are shown,
 408                                 including both the start and the end
 409                                 value of the range. This will add
 410                                 <literal>PRIORITY=</literal> matches
 411                                 for the specified
 412                                 priorities.</para></listitem>
 413                         </varlistentry>
 414
 415                         <varlistentry>
 416                                 <term><option>-c</option></term>
 417                                 <term><option>--cursor=</option></term>
 418
 419                                 <listitem><para>Start showing entries
 420                                 from the location in the journal
 421                                 specified by the passed
 422                                 cursor.</para></listitem>
 423                         </varlistentry>
 424
 425                         <varlistentry>
 426                                 <term><option>--since=</option></term>
 427                                 <term><option>--until=</option></term>
 428
 429                                 <listitem><para>Start showing entries
 430                                 on or newer than the specified date,
 431                                 or on or older than the specified
 432                                 date, respectively. Date specifications
 433                                 should be of the format
 434                                 <literal>2012-10-30 18:17:16</literal>.
 435                                 If the time part is omitted,
 436                                 <literal>00:00:00</literal> is assumed.
 437                                 If only the seconds component is omitted,
 438                                 <literal>:00</literal> is assumed. If the
 439                                 date component is omitted, the current
 440                                 day is assumed. Alternatively the strings
 441                                 <literal>yesterday</literal>,
 442                                 <literal>today</literal>,
 443                                 <literal>tomorrow</literal> are
 444                                 understood, which refer to 00:00:00 of
 445                                 the day before the current day, the
 446                                 current day, or the day after the
 447                                 current day, respectively. <literal>now</literal>
 448                                 refers to the current time. Finally,
 449                                 relative times may be specified,
 450                                 prefixed with <literal>-</literal> or
 451                                 <literal>+</literal>, referring to
 452                                 times before or after the current
 453                                 time, respectively.</para></listitem>
 454                         </varlistentry>
 455
 456                         <varlistentry>
 457                                 <term><option>-F</option></term>
 458                                 <term><option>--field=</option></term>
 459
 460                                 <listitem><para>Print all possible
 461                                 data values the specified field can
 462                                 take in all entries of the
 463                                 journal.</para></listitem>
 464                         </varlistentry>
 465
 466                         <varlistentry>
 467                                 <term><option>--system</option></term>
 468                                 <term><option>--user</option></term>
 469
 470                                 <listitem><para>Show messages from
 471                                 system services and the kernel (with
 472                                 <option>--system</option>).  Show
 473                                 messages from service of current user
 474                                 (with <option>--user</option>).
 475                                 If neither is specified, show all
 476                                 messages that the user can see.
 477                                 </para></listitem>
 478                         </varlistentry>
 479
 480                         <varlistentry>
 481                                 <term><option>-D <replaceable>DIR</replaceable></option></term>
 482                                 <term><option>--directory=<replaceable>DIR</replaceable></option></term>
 483
 484                                 <listitem><para>Takes a directory path
 485                                 as argument. If specified, journalctl
 486                                 will operate on the specified journal
 487                                 directory
 488                                 <replaceable>DIR</replaceable> instead
 489                                 of the default runtime and system
 490                                 journal paths.</para></listitem>
 491                         </varlistentry>
 492
 493                         <varlistentry>
 494                                 <term><option>--file=<replaceable>GLOB</replaceable></option></term>
 495
 496                                 <listitem><para>Takes a file glob as
 497                                 argument. If specified, journalctl will
 498                                 operate on the specified journal files
 499                                 matching <replaceable>GLOB</replaceable>
 500                                 instead of the default runtime and
 501                                 system journal paths. May be specified
 502                                 multiple times, in which case files will
 503                                 be suitably interleaved.</para></listitem>
 504                         </varlistentry>
 505
 506                         <varlistentry>
 507                                 <term><option>--root=<replaceable>ROOT</replaceable></option></term>
 508
 509                                 <listitem><para>Takes a directory path
 510                                 as argument. If specified, journalctl
 511                                 will operate on catalog file hierarchy
 512                                 underneath the specified directory
 513                                 instead of the root directory
 514                                 (e.g. <option>--update-catalog</option>
 515                                 will create
 516                                 <filename><replaceable>ROOT</replaceable>/var/lib/systemd/catalog/database</filename>).
 517                                 </para></listitem>
 518                         </varlistentry>
 519
 520                         <varlistentry>
 521                                 <term><option>--new-id128</option></term>
 522
 523                                 <listitem><para>Instead of showing
 524                                 journal contents, generate a new 128
 525                                 bit ID suitable for identifying
 526                                 messages. This is intended for usage
 527                                 by developers who need a new
 528                                 identifier for a new message they
 529                                 introduce and want to make
 530                                 recognizable. This will print the new ID in
 531                                 three different formats which can be
 532                                 copied into source code or
 533                                 similar.</para></listitem>
 534                         </varlistentry>
 535
 536                         <varlistentry>
 537                                 <term><option>--header</option></term>
 538
 539                                 <listitem><para>Instead of showing
 540                                 journal contents, show internal header
 541                                 information of the journal fields
 542                                 accessed.</para></listitem>
 543                         </varlistentry>
 544
 545                         <varlistentry>
 546                                 <term><option>--disk-usage</option></term>
 547
 548                                 <listitem><para>Shows the current disk
 549                                 usage of all
 550                                 journal files.</para></listitem>
 551                         </varlistentry>
 552
 553                         <varlistentry>
 554                                 <term><option>--list-catalog
 555                                 <optional><replaceable>ID128...</replaceable></optional>
 556                                 </option></term>
 557
 558                                 <listitem><para>List the contents of
 559                                 the message catalog, as table of
 560                                 message IDs plus their short
 561                                 description strings.</para>
 562
 563                                 <para>If any
 564                                 <replaceable>ID128</replaceable>s are
 565                                 specified, only those entries are shown.
 566                                 </para>
 567                                 </listitem>
 568                         </varlistentry>
 569
 570                         <varlistentry>
 571                                 <term><option>--dump-catalog
 572                                 <optional><replaceable>ID128...</replaceable></optional>
 573                                 </option></term>
 574
 575                                 <listitem><para>Show the contents of
 576                                 the message catalog, with entries
 577                                 separated by a line consisting of two
 578                                 dashes and the id (the format is the
 579                                 same as <filename>.catalog</filename>
 580                                 files.</para>
 581
 582                                 <para>If any
 583                                 <replaceable>ID128</replaceable>s are
 584                                 specified, only those entries are shown.
 585                                 </para>
 586                                 </listitem>
 587                         </varlistentry>
 588
 589                         <varlistentry>
 590                                 <term><option>--update-catalog</option></term>
 591
 592                                 <listitem><para>Update the message
 593                                 catalog index. This command needs to
 594                                 be executed each time new catalog
 595                                 files are installed, removed or
 596                                 updated to rebuild the binary catalog
 597                                 index.</para></listitem>
 598                         </varlistentry>
 599
 600                         <varlistentry>
 601                                 <term><option>--setup-keys</option></term>
 602
 603                                 <listitem><para>Instead of showing
 604                                 journal contents, generate a new key
 605                                 pair for Forward Secure Sealing
 606                                 (FSS). This will generate a sealing
 607                                 key and a verification key. The
 608                                 sealing key is stored in the journal
 609                                 data directory and shall remain on the
 610                                 host. The verification key should be
 611                                 stored externally. Also see the
 612                                 <option>Seal=</option> option in
 613                                 <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 614                                 for details.</para></listitem>
 615                         </varlistentry>
 616
 617                         <varlistentry>
 618                                 <term><option>--force</option></term>
 619
 620                                 <listitem><para>When --setup-keys is passed and
 621                                 Forward Secure Sealing has already been set up,
 622                                 recreate FSS keys.</para></listitem>
 623                         </varlistentry>
 624
 625                         <varlistentry>
 626                                 <term><option>--interval=</option></term>
 627
 628                                 <listitem><para>Specifies the change
 629                                 interval for the sealing key when
 630                                 generating an FSS key pair with
 631                                 <option>--setup-keys</option>. Shorter
 632                                 intervals increase CPU consumption but
 633                                 shorten the time range of
 634                                 undetectable journal
 635                                 alterations. Defaults to
 636                                 15min.</para></listitem>
 637                         </varlistentry>
 638
 639                         <varlistentry>
 640                                 <term><option>--verify</option></term>
 641
 642                                 <listitem><para>Check the journal file
 643                                 for internal consistency. If the
 644                                 file has been generated with FSS
 645                                 enabled and the FSS verification key
 646                                 has been specified with
 647                                 <option>--verify-key=</option>,
 648                                 authenticity of the journal file is
 649                                 verified.</para></listitem>
 650                         </varlistentry>
 651
 652                         <varlistentry>
 653                                 <term><option>--verify-key=</option></term>
 654
 655                                 <listitem><para>Specifies the FSS
 656                                 verification key to use for the
 657                                 <option>--verify</option>
 658                                 operation.</para></listitem>
 659                         </varlistentry>
 660
 661                 </variablelist>
 662         </refsect1>
 663
 664         <refsect1>
 665                 <title>Exit status</title>
 666
 667                 <para>On success, 0 is returned, a non-zero failure
 668                 code otherwise.</para>
 669         </refsect1>
 670
 671         <refsect1>
 672                 <title>Environment</title>
 673
 674                 <variablelist class='environment-variables'>
 675                         <varlistentry>
 676                                 <term><varname>$SYSTEMD_PAGER</varname></term>
 677                                 <listitem><para>Pager to use when
 678                                 <option>--no-pager</option> is not given;
 679                                 overrides <varname>$PAGER</varname>.  Setting
 680                                 this to an empty string or the value
 681                                 <literal>cat</literal> is equivalent to passing
 682                                 <option>--no-pager</option>.</para></listitem>
 683                         </varlistentry>
 684                 </variablelist>
 685         </refsect1>
 686
 687         <refsect1>
 688                 <title>Examples</title>
 689
 690                 <para>Without arguments, all collected logs are shown
 691                 unfiltered:</para>
 692
 693                 <programlisting>journalctl</programlisting>
 694
 695                 <para>With one match specified, all entries with a field matching the expression are shown:</para>
 696
 697                 <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service</programlisting>
 698
 699                 <para>If two different fields are matched, only entries matching both expressions at the same time are shown:</para>
 700
 701                 <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=28097</programlisting>
 702
 703                 <para>If two matches refer to the same field, all entries matching either expression are shown:</para>
 704
 705                 <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _SYSTEMD_UNIT=dbus.service</programlisting>
 706
 707                 <para>If the separator <literal>+</literal> is used,
 708                 two expressions may be combined in a logical OR. The
 709                 following will show all messages from the Avahi
 710                 service process with the PID 28097 plus all messages
 711                 from the D-Bus service (from any of its
 712                 processes):</para>
 713
 714                 <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=28097 + _SYSTEMD_UNIT=dbus.service</programlisting>
 715
 716                 <para>Show all logs generated by the D-Bus executable:</para>
 717
 718                 <programlisting>journalctl /usr/bin/dbus-daemon</programlisting>
 719
 720                 <para>Show all logs of the kernel device node <filename noindex='true'>/dev/sda</filename>:</para>
 721
 722                 <programlisting>journalctl /dev/sda</programlisting>
 723
 724         </refsect1>
 725
 726         <refsect1>
 727                 <title>See Also</title>
 728                 <para>
 729                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 730                         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 731                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 732                         <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 733                         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 734                 </para>
 735         </refsect1>
 736
 737 </refentry>