man/tmpfiles.d.xml

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   8   Copyright 2010 Brandon Philips
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  23 <refentry id="tmpfiles.d">
  24
  25   <refentryinfo>
  26     <title>tmpfiles.d</title>
  27     <productname>systemd</productname>
  28
  29     <authorgroup>
  30       <author>
  31         <contrib>Documentation</contrib>
  32         <firstname>Brandon</firstname>
  33         <surname>Philips</surname>
  34         <email>brandon@ifup.org</email>
  35       </author>
  36     </authorgroup>
  37   </refentryinfo>
  38
  39   <refmeta>
  40     <refentrytitle>tmpfiles.d</refentrytitle>
  41     <manvolnum>5</manvolnum>
  42   </refmeta>
  43
  44   <refnamediv>
  45     <refname>tmpfiles.d</refname>
  46     <refpurpose>Configuration for creation, deletion and cleaning of
  47     volatile and temporary files</refpurpose>
  48   </refnamediv>
  49
  50   <refsynopsisdiv>
  51     <para><filename>/etc/tmpfiles.d/*.conf</filename></para>
  52     <para><filename>/run/tmpfiles.d/*.conf</filename></para>
  53     <para><filename>/usr/lib/tmpfiles.d/*.conf</filename></para>
  54   </refsynopsisdiv>
  55
  56   <refsect1>
  57     <title>Description</title>
  58
  59     <para><command>systemd-tmpfiles</command> uses the configuration
  60     files from the above directories to describe the creation,
  61     cleaning and removal of volatile and temporary files and
  62     directories which usually reside in directories such as
  63     <filename>/run</filename> or <filename>/tmp</filename>.</para>
  64
  65     <para>Volatile and temporary files and directories are those
  66     located in <filename>/run</filename> (and its alias
  67     <filename>/var/run</filename>), <filename>/tmp</filename>,
  68     <filename>/var/tmp</filename>, the API file systems such as
  69     <filename>/sys</filename> or <filename>/proc</filename>, as well
  70     as some other directories below <filename>/var</filename>.</para>
  71
  72     <para>System daemons frequently require private runtime
  73     directories below <filename>/run</filename> to place communication
  74     sockets and similar in. For these, consider declaring them in
  75     their unit files using <varname>RuntimeDirectory=</varname> (see
  76     <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  77     for details), if this is feasible.</para>
  78   </refsect1>
  79
  80   <refsect1>
  81     <title>Configuration Directories and Precedence</title>
  82
  83     <para>Each configuration file shall be named in the style of
  84     <filename><replaceable>package</replaceable>.conf</filename> or
  85     <filename><replaceable>package</replaceable>-<replaceable>part</replaceable>.conf</filename>.
  86     The second variant should be used when it is desirable to make it
  87     easy to override just this part of configuration.</para>
  88
  89     <para>Files in <filename>/etc/tmpfiles.d</filename> override files
  90     with the same name in <filename>/usr/lib/tmpfiles.d</filename> and
  91     <filename>/run/tmpfiles.d</filename>. Files in
  92     <filename>/run/tmpfiles.d</filename> override files with the same
  93     name in <filename>/usr/lib/tmpfiles.d</filename>. Packages should
  94     install their configuration files in
  95     <filename>/usr/lib/tmpfiles.d</filename>. Files in
  96     <filename>/etc/tmpfiles.d</filename> are reserved for the local
  97     administrator, who may use this logic to override the
  98     configuration files installed by vendor packages. All
  99     configuration files are sorted by their filename in lexicographic
 100     order, regardless of which of the directories they reside in. If
 101     multiple files specify the same path, the entry in the file with
 102     the lexicographically earliest name will be applied.  All other
 103     conflicting entries will be logged as errors. When two lines are
 104     prefix and suffix of each other, then the prefix is always
 105     processed first, the suffix later. Lines that take globs are
 106     applied after those accepting no globs. If multiple operations
 107     shall be applied on the same file, (such as ACL, xattr, file
 108     attribute adjustments), these are always done in the same fixed
 109     order. Otherwise, the files/directories are processed in the order
 110     they are listed.</para>
 111
 112     <para>If the administrator wants to disable a configuration file
 113     supplied by the vendor, the recommended way is to place a symlink
 114     to <filename>/dev/null</filename> in
 115     <filename>/etc/tmpfiles.d/</filename> bearing the same filename.
 116     </para>
 117   </refsect1>
 118
 119   <refsect1>
 120     <title>Configuration File Format</title>
 121
 122     <para>The configuration format is one line per path containing
 123     type, path, mode, ownership, age, and argument fields:</para>
 124
 125     <programlisting>#Type Path        Mode UID  GID  Age Argument
 126 d     /run/user   0755 root root 10d -
 127 L     /tmp/foobar -    -    -    -   /dev/null</programlisting>
 128
 129     <para>Fields may be enclosed within quotes and contain C-style escapes.</para>
 130
 131     <refsect2>
 132       <title>Type</title>
 133
 134       <para>The type consists of a single letter and optionally an
 135       exclamation mark.</para>
 136
 137       <para>The following line types are understood:</para>
 138
 139       <variablelist>
 140         <varlistentry>
 141           <term><varname>f</varname></term>
 142           <listitem><para>Create a file if it does not exist yet. If
 143           the argument parameter is given, it will be written to the
 144           file. Does not follow symlinks.</para></listitem>
 145         </varlistentry>
 146
 147         <varlistentry>
 148           <term><varname>F</varname></term>
 149           <listitem><para>Create or truncate a file. If the argument
 150           parameter is given, it will be written to the file. Does not follow symlinks.</para>
 151           </listitem>
 152         </varlistentry>
 153
 154         <varlistentry>
 155           <term><varname>w</varname></term>
 156           <listitem><para>Write the argument parameter to a file, if
 157           the file exists.  Lines of this type accept shell-style
 158           globs in place of normal path names. The argument parameter
 159           will be written without a trailing newline. C-style
 160           backslash escapes are interpreted. Follows
 161           symlinks.</para></listitem>
 162         </varlistentry>
 163
 164         <varlistentry>
 165           <term><varname>d</varname></term>
 166           <listitem><para>Create a directory. The mode and ownership will be adjusted if
 167           specified and the directory already exists. Contents of this directory are subject
 168           to time based cleanup if the age argument is specified.</para></listitem>
 169         </varlistentry>
 170
 171         <varlistentry>
 172           <term><varname>D</varname></term>
 173           <listitem><para>Similar to <varname>d</varname>, but in addition the contents
 174           of the directory will be removed when <option>--remove</option> is used.
 175           </para></listitem>
 176         </varlistentry>
 177
 178         <varlistentry>
 179           <term><varname>e</varname></term>
 180           <listitem><para>Similar to <varname>d</varname>, but the directory will not be created if
 181           it does not exist. Lines of this type accept shell-style globs in place of normal path
 182           names. For this entry to be useful, at least one of the mode, uid, gid, or age arguments
 183           must be specified, since otherwise this entry has no effect. If the age argument is
 184           <literal>0</literal>, contents of the directory will be unconditionally deleted every time
 185           <command>systemd-tmpfiles --clean</command> is run. This can be useful when combined with
 186           <varname>!</varname>, see the examples.</para></listitem>
 187         </varlistentry>
 188
 189         <varlistentry>
 190           <term><varname>v</varname></term>
 191           <listitem><para>Create a subvolume if the path does not
 192           exist yet, the file system supports subvolumes (btrfs), and
 193           the system itself is installed into a subvolume
 194           (specifically: the root directory <filename>/</filename> is
 195           itself a subvolume). Otherwise, create a normal directory, in
 196           the same way as <varname>d</varname>. A subvolume created
 197           with this line type is not assigned to any higher-level
 198           quota group. For that, use <varname>q</varname> or
 199           <varname>Q</varname>, which allow creating simple quota
 200           group hierarchies, see below.</para></listitem>
 201         </varlistentry>
 202
 203         <varlistentry>
 204           <term><varname>q</varname></term>
 205           <listitem><para>Similar to <varname>v</varname>. However,
 206           makes sure that the subvolume will be assigned to the same
 207           higher-level quota groups as the subvolume it has been
 208           created in. This ensures that higher-level limits and
 209           accounting applied to the parent subvolume also include the
 210           specified subvolume. On non-btrfs file systems, this line
 211           type is identical to <varname>d</varname>. If the subvolume
 212           already exists and is already assigned to one or more higher
 213           level quota groups, no change to the quota hierarchy is
 214           made. Also see <varname>Q</varname> below. See <citerefentry
 215           project='die-net'><refentrytitle>btrfs-qgroup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 216           for details about the btrfs quota group
 217           concept.</para></listitem>
 218         </varlistentry>
 219
 220         <varlistentry>
 221           <term><varname>Q</varname></term>
 222           <listitem><para>Similar to <varname>q</varname>. However,
 223           instead of copying the higher-level quota group assignments
 224           from the parent as-is, the lowest quota group of the parent
 225           subvolume is determined that is not the leaf quota
 226           group. Then, an "intermediary" quota group is inserted that
 227           is one level below this level, and shares the same ID part
 228           as the specified subvolume. If no higher-level quota group
 229           exists for the parent subvolume, a new quota group at level
 230           255 sharing the same ID as the specified subvolume is
 231           inserted instead. This new intermediary quota group is then
 232           assigned to the parent subvolume's higher-level quota
 233           groups, and the specified subvolume's leaf quota group is
 234           assigned to it.</para>
 235
 236           <para>Effectively, this has a similar effect as
 237           <varname>q</varname>, however introduces a new higher-level
 238           quota group for the specified subvolume that may be used to
 239           enforce limits and accounting to the specified subvolume and
 240           children subvolume created within it. Thus, by creating
 241           subvolumes only via <varname>q</varname> and
 242           <varname>Q</varname>, a concept of "subtree quotas" is
 243           implemented. Each subvolume for which <varname>Q</varname>
 244           is set will get a "subtree" quota group created, and all
 245           child subvolumes created within it will be assigned to
 246           it. Each subvolume for which <varname>q</varname> is set
 247           will not get such a "subtree" quota group, but it is ensured
 248           that they are added to the same "subtree" quota group as their
 249           immediate parents.</para>
 250
 251           <para>It is recommended to use
 252           <varname>Q</varname> for subvolumes that typically contain
 253           further subvolumes, and where it is desirable to have
 254           accounting and quota limits on all child subvolumes
 255           together. Examples for <varname>Q</varname> are typically
 256           <filename>/home</filename> or
 257           <filename>/var/lib/machines</filename>. In contrast,
 258           <varname>q</varname> should be used for subvolumes that
 259           either usually do not include further subvolumes or where no
 260           accounting and quota limits are needed that apply to all
 261           child subvolumes together. Examples for <varname>q</varname>
 262           are typically <filename>/var</filename> or
 263           <filename>/var/tmp</filename>. As with <varname>Q</varname>,
 264           <varname>q</varname> has no effect on the quota group
 265           hierarchy if the subvolume exists and already has at least
 266           one higher-level quota group assigned.</para></listitem>
 267         </varlistentry>
 268
 269         <varlistentry>
 270           <term><varname>p</varname></term>
 271           <term><varname>p+</varname></term>
 272           <listitem><para>Create a named pipe (FIFO) if it does not
 273           exist yet. If suffixed with <varname>+</varname> and a file
 274           already exists where the pipe is to be created, it will be
 275           removed and be replaced by the pipe.</para></listitem>
 276         </varlistentry>
 277
 278         <varlistentry>
 279           <term><varname>L</varname></term>
 280           <term><varname>L+</varname></term>
 281           <listitem><para>Create a symlink if it does not exist
 282           yet. If suffixed with <varname>+</varname> and a file or
 283           directory already exists where the symlink is to be created,
 284           it will be removed and be replaced by the symlink. If the
 285           argument is omitted, symlinks to files with the same name
 286           residing in the directory
 287           <filename>/usr/share/factory/</filename> are created. Note
 288           that permissions and ownership on symlinks are ignored.
 289           </para></listitem>
 290         </varlistentry>
 291
 292         <varlistentry>
 293           <term><varname>c</varname></term>
 294           <term><varname>c+</varname></term>
 295           <listitem><para>Create a character device node if it does
 296           not exist yet. If suffixed with <varname>+</varname> and a
 297           file already exists where the device node is to be created,
 298           it will be removed and be replaced by the device node. It is
 299           recommended to suffix this entry with an exclamation mark to
 300           only create static device nodes at boot, as udev will not
 301           manage static device nodes that are created at runtime.
 302           </para></listitem>
 303         </varlistentry>
 304
 305         <varlistentry>
 306           <term><varname>b</varname></term>
 307           <term><varname>b+</varname></term>
 308           <listitem><para>Create a block device node if it does not
 309           exist yet. If suffixed with <varname>+</varname> and a file
 310           already exists where the device node is to be created, it
 311           will be removed and be replaced by the device node. It is
 312           recommended to suffix this entry with an exclamation mark to
 313           only create static device nodes at boot, as udev will not
 314           manage static device nodes that are created at runtime.
 315           </para></listitem>
 316         </varlistentry>
 317
 318         <varlistentry>
 319           <term><varname>C</varname></term>
 320           <listitem><para>Recursively copy a file or directory, if the
 321           destination files or directories do not exist yet. Note that
 322           this command will not descend into subdirectories if the
 323           destination directory already exists. Instead, the entire
 324           copy operation is skipped. If the argument is omitted, files
 325           from the source directory
 326           <filename>/usr/share/factory/</filename> with the same name
 327           are copied. Does not follow symlinks.</para></listitem>
 328         </varlistentry>
 329
 330         <varlistentry>
 331           <term><varname>x</varname></term>
 332           <listitem><para>Ignore a path during cleaning. Use this type
 333           to exclude paths from clean-up as controlled with the Age
 334           parameter. Note that lines of this type do not influence the
 335           effect of <varname>r</varname> or <varname>R</varname>
 336           lines. Lines of this type accept shell-style globs in place
 337           of normal path names.  </para></listitem>
 338         </varlistentry>
 339
 340         <varlistentry>
 341           <term><varname>X</varname></term>
 342           <listitem><para>Ignore a path during cleaning. Use this type
 343           to exclude paths from clean-up as controlled with the Age
 344           parameter. Unlike <varname>x</varname>, this parameter will
 345           not exclude the content if path is a directory, but only
 346           directory itself. Note that lines of this type do not
 347           influence the effect of <varname>r</varname> or
 348           <varname>R</varname> lines. Lines of this type accept
 349           shell-style globs in place of normal path names.
 350           </para></listitem>
 351         </varlistentry>
 352
 353         <varlistentry>
 354           <term><varname>r</varname></term>
 355           <listitem><para>Remove a file or directory if it exists.
 356           This may not be used to remove non-empty directories, use
 357           <varname>R</varname> for that.  Lines of this type accept
 358           shell-style globs in place of normal path
 359           names. Does not follow symlinks.</para></listitem>
 360         </varlistentry>
 361
 362         <varlistentry>
 363           <term><varname>R</varname></term>
 364           <listitem><para>Recursively remove a path and all its
 365           subdirectories (if it is a directory). Lines of this type
 366           accept shell-style globs in place of normal path
 367           names. Does not follow symlinks.</para></listitem>
 368         </varlistentry>
 369
 370         <varlistentry>
 371           <term><varname>z</varname></term>
 372           <listitem><para>Adjust the access mode, group and user, and
 373           restore the SELinux security context of a file or directory,
 374           if it exists. Lines of this type accept shell-style globs in
 375           place of normal path names. Does not follow symlinks.</para></listitem>
 376         </varlistentry>
 377
 378         <varlistentry>
 379           <term><varname>Z</varname></term>
 380           <listitem><para>Recursively set the access mode, group and
 381           user, and restore the SELinux security context of a file or
 382           directory if it exists, as well as of its subdirectories and
 383           the files contained therein (if applicable). Lines of this
 384           type accept shell-style globs in place of normal path
 385           names. Does not follow symlinks.  </para></listitem>
 386         </varlistentry>
 387
 388         <varlistentry>
 389           <term><varname>t</varname></term>
 390           <listitem><para>Set extended attributes. Lines of this type
 391           accept shell-style globs in place of normal path names.
 392           This can be useful for setting SMACK labels. Does not follow
 393           symlinks.</para></listitem>
 394         </varlistentry>
 395
 396         <varlistentry>
 397           <term><varname>T</varname></term>
 398           <listitem><para>Recursively set extended attributes. Lines
 399           of this type accept shell-style globs in place of normal
 400           path names.  This can be useful for setting SMACK
 401           labels. Does not follow symlinks.  </para></listitem>
 402         </varlistentry>
 403
 404         <varlistentry>
 405           <term><varname>h</varname></term>
 406           <listitem><para>Set file/directory attributes. Lines of this type
 407           accept shell-style globs in place of normal path names.</para>
 408
 409           <para>The format of the argument field is
 410           <varname>[+-=][aAcCdDeijsStTu] </varname>. The prefix
 411           <varname>+</varname> (the default one) causes the
 412           attribute(s) to be added; <varname>-</varname> causes the
 413           attribute(s) to be removed; <varname>=</varname> causes the
 414           attributes to be set exactly as the following letters. The
 415           letters <literal>aAcCdDeijsStTu</literal> select the new
 416           attributes for the files, see
 417           <citerefentry project='man-pages'><refentrytitle>chattr</refentrytitle>
 418           <manvolnum>1</manvolnum></citerefentry> for further information.
 419           </para>
 420           <para>Passing only <varname>=</varname> as argument resets
 421           all the file attributes listed above. It has to be pointed
 422           out that the <varname>=</varname> prefix limits itself to
 423           the attributes corresponding to the letters listed here. All
 424           other attributes will be left untouched. Does not follow
 425           symlinks.</para>
 426           </listitem>
 427         </varlistentry>
 428
 429         <varlistentry>
 430           <term><varname>H</varname></term>
 431           <listitem><para>Recursively set file/directory attributes. Lines
 432           of this type accept shell-style globs in place of normal
 433           path names. Does not follow symlinks.
 434           </para></listitem>
 435         </varlistentry>
 436
 437         <varlistentry>
 438           <term><varname>a</varname></term>
 439           <term><varname>a+</varname></term>
 440           <listitem><para>Set POSIX ACLs (access control lists). If
 441           suffixed with <varname>+</varname>, the specified entries will
 442           be added to the existing set.
 443           <command>systemd-tmpfiles</command> will automatically add
 444           the required base entries for user and group based on the
 445           access mode of the file, unless base entries already exist
 446           or are explicitly specified. The mask will be added if not
 447           specified explicitly or already present. Lines of this type
 448           accept shell-style globs in place of normal path names. This
 449           can be useful for allowing additional access to certain
 450           files. Does not follow symlinks.</para></listitem>
 451         </varlistentry>
 452
 453         <varlistentry>
 454           <term><varname>A</varname></term>
 455           <term><varname>A+</varname></term>
 456           <listitem><para>Same as <varname>a</varname> and
 457           <varname>a+</varname>, but recursive. Does not follow
 458           symlinks.</para></listitem>
 459         </varlistentry>
 460       </variablelist>
 461
 462       <para>If the exclamation mark is used, this line is only safe of
 463       execute during boot, and can break a running system. Lines
 464       without the exclamation mark are presumed to be safe to execute
 465       at any time, e.g. on package upgrades.
 466       <command>systemd-tmpfiles</command> will execute line with an
 467       exclamation mark only if option <option>--boot</option> is
 468       given.</para>
 469
 470       <para>For example:
 471       <programlisting># Make sure these are created by default so that nobody else can
 472 d /tmp/.X11-unix 1777 root root 10d
 473
 474 # Unlink the X11 lock files
 475 r! /tmp/.X[0-9]*-lock</programlisting>
 476       The second line in contrast to the first one would break a
 477       running system, and will only be executed with
 478       <option>--boot</option>.</para>
 479     </refsect2>
 480
 481     <refsect2>
 482       <title>Path</title>
 483
 484       <para>The file system path specification supports simple
 485       specifier expansion, see below. The path (after expansion) must be
 486       absolute.</para>
 487     </refsect2>
 488
 489     <refsect2>
 490       <title>Mode</title>
 491
 492       <para>The file access mode to use when creating this file or
 493       directory. If omitted or when set to <literal>-</literal>, the
 494       default is used: 0755 for directories, 0644 for all other file
 495       objects.  For <varname>z</varname>, <varname>Z</varname> lines,
 496       if omitted or when set to <literal>-</literal>, the file access
 497       mode will not be modified. This parameter is ignored for
 498       <varname>x</varname>, <varname>r</varname>,
 499       <varname>R</varname>, <varname>L</varname>, <varname>t</varname>,
 500       and <varname>a</varname> lines.</para>
 501
 502       <para>Optionally, if prefixed with <literal>~</literal>, the
 503       access mode is masked based on the already set access bits for
 504       existing file or directories: if the existing file has all
 505       executable bits unset, all executable bits are removed from the
 506       new access mode, too. Similarly, if all read bits are removed
 507       from the old access mode, they will be removed from the new
 508       access mode too, and if all write bits are removed, they will be
 509       removed from the new access mode too. In addition, the
 510       sticky/SUID/SGID bit is removed unless applied to a
 511       directory. This functionality is particularly useful in
 512       conjunction with <varname>Z</varname>.</para>
 513     </refsect2>
 514
 515     <refsect2>
 516       <title>UID, GID</title>
 517
 518       <para>The user and group to use for this file or directory. This
 519       may either be a numeric user/group ID or a user or group
 520       name. If omitted or when set to <literal>-</literal>, the
 521       default 0 (root) is used. For <varname>z</varname> and
 522       <varname>Z</varname> lines, when omitted or when set to
 523       <literal>-</literal>, the file ownership will not be
 524       modified. These parameters are ignored for <varname>x</varname>,
 525       <varname>r</varname>, <varname>R</varname>,
 526       <varname>L</varname>, <varname>t</varname>, and
 527       <varname>a</varname> lines.</para>
 528     </refsect2>
 529
 530     <refsect2>
 531       <title>Age</title>
 532       <para>The date field, when set, is used to decide what files to
 533       delete when cleaning. If a file or directory is older than the
 534       current time minus the age field, it is deleted. The field
 535       format is a series of integers each followed by one of the
 536       following suffixes for the respective time units:
 537       <constant>s</constant>,
 538       <constant>m</constant> or <constant>min</constant>,
 539       <constant>h</constant>,
 540       <constant>d</constant>,
 541       <constant>w</constant>,
 542       <constant>ms</constant>, and
 543       <constant>us</constant>,
 544       meaning seconds, minutes, hours, days, weeks,
 545       milliseconds, and microseconds, respectively. Full names of the time units can
 546       be used too.
 547       </para>
 548
 549       <para>If multiple integers and units are specified, the time
 550       values are summed. If an integer is given without a unit,
 551       <constant>s</constant> is assumed.
 552       </para>
 553
 554       <para>When the age is set to zero, the files are cleaned
 555       unconditionally.</para>
 556
 557       <para>The age field only applies to lines starting with
 558       <varname>d</varname>, <varname>D</varname>, <varname>e</varname>,
 559       <varname>v</varname>, <varname>q</varname>,
 560       <varname>Q</varname>, <varname>C</varname>, <varname>x</varname>
 561       and <varname>X</varname>. If omitted or set to
 562       <literal>-</literal>, no automatic clean-up is done.</para>
 563
 564       <para>If the age field starts with a tilde character
 565       <literal>~</literal>, the clean-up is only applied to files and
 566       directories one level inside the directory specified, but not
 567       the files and directories immediately inside it.</para>
 568     </refsect2>
 569
 570     <refsect2>
 571       <title>Argument</title>
 572
 573       <para>For <varname>L</varname> lines determines the destination
 574       path of the symlink. For <varname>c</varname> and
 575       <varname>b</varname>, determines the major/minor of the device
 576       node, with major and minor formatted as integers, separated by
 577       <literal>:</literal>, e.g.  <literal>1:3</literal>. For
 578       <varname>f</varname>, <varname>F</varname>, and
 579       <varname>w</varname>, the argument may be used to specify a short string that
 580       is written to the file, suffixed by a newline. For
 581       <varname>C</varname>, specifies the source file or
 582       directory. For <varname>t</varname> and <varname>T</varname>,
 583       determines extended attributes to be set. For
 584       <varname>a</varname> and <varname>A</varname>, determines ACL
 585       attributes to be set. For <varname>h</varname> and
 586       <varname>H</varname>, determines the file attributes to
 587       set. Ignored for all other lines.</para>
 588
 589       <para>This field can contain specifiers, see below.</para>
 590     </refsect2>
 591   </refsect1>
 592
 593   <refsect1>
 594     <title>Specifiers</title>
 595
 596     <para>Specifiers can be used in the "path" and "argument" fields.
 597     The following expansions are understood:</para>
 598       <table>
 599         <title>Specifiers available</title>
 600         <tgroup cols='3' align='left' colsep='1' rowsep='1'>
 601           <colspec colname="spec" />
 602           <colspec colname="mean" />
 603           <colspec colname="detail" />
 604           <thead>
 605             <row>
 606               <entry>Specifier</entry>
 607               <entry>Meaning</entry>
 608               <entry>Details</entry>
 609             </row>
 610           </thead>
 611           <tbody>
 612             <row>
 613               <entry><literal>%m</literal></entry>
 614               <entry>Machine ID</entry>
 615               <entry>The machine ID of the running system, formatted as string. See <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information.</entry>
 616             </row>
 617             <row>
 618               <entry><literal>%b</literal></entry>
 619               <entry>Boot ID</entry>
 620               <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
 621             </row>
 622             <row>
 623               <entry><literal>%H</literal></entry>
 624               <entry>Host name</entry>
 625               <entry>The hostname of the running system.</entry>
 626             </row>
 627             <row>
 628               <entry><literal>%v</literal></entry>
 629               <entry>Kernel release</entry>
 630               <entry>Identical to <command>uname -r</command> output.</entry>
 631             </row>
 632             <row>
 633               <entry><literal>%%</literal></entry>
 634               <entry>Escaped %</entry>
 635               <entry>Single percent sign.</entry>
 636             </row>
 637           </tbody>
 638         </tgroup>
 639       </table>
 640   </refsect1>
 641
 642   <refsect1>
 643     <title>Examples</title>
 644     <example>
 645       <title>Create directories with specific mode and ownership</title>
 646       <para>
 647       <citerefentry project='die-net'><refentrytitle>screen</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 648       needs two directories created at boot with specific modes and ownership:</para>
 649
 650       <programlisting># /usr/lib/tmpfiles.d/screen.conf
 651 d /run/screens  1777 root screen 10d
 652 d /run/uscreens 0755 root screen 10d12h
 653 </programlisting>
 654
 655       <para>Contents of <filename>/run/screens</filename> and /run/uscreens will
 656       cleaned up after 10 and 10½ days, respectively.</para>
 657     </example>
 658
 659     <example>
 660       <title>Create a directory with a SMACK attribute</title>
 661       <programlisting>D /run/cups - - - -
 662 t /run/cups - - - - security.SMACK64=printing user.attr-with-spaces="foo bar"
 663       </programlisting>
 664
 665       <para>The directory will be owned by root and have default mode. Its contents are
 666       not subject to time based cleanup, but will be obliterated when
 667       <command>systemd-tmpfiles --remove</command> runs.</para>
 668     </example>
 669
 670     <example>
 671       <title>Create a directory and prevent its contents from cleanup</title>
 672       <para>
 673       <citerefentry project='die-net'><refentrytitle>abrt</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 674       needs a directory created at boot with specific mode and ownership and its content
 675       should be preserved from the automatic cleanup applied to the contents of
 676       <filename>/var/tmp</filename>:</para>
 677
 678       <programlisting># /usr/lib/tmpfiles.d/tmp.conf
 679 d /var/tmp 1777 root root 30d
 680 </programlisting>
 681
 682       <programlisting># /usr/lib/tmpfiles.d/abrt.conf
 683 d /var/tmp/abrt 0755 abrt abrt -
 684 </programlisting>
 685     </example>
 686
 687     <example>
 688       <title>Apply clean up during boot and based on time</title>
 689
 690       <programlisting># /usr/lib/tmpfiles.d/dnf.conf
 691 r! /var/cache/dnf/*/*/download_lock.pid
 692 r! /var/cache/dnf/*/*/metadata_lock.pid
 693 r! /var/lib/dnf/rpmdb_lock.pid
 694 e  /var/cache/dnf/ - - - 30d
 695 </programlisting>
 696
 697      <para>The lock files will be removed during boot. Any files and directories in
 698      <filename>/var/cache/dnf/</filename> will be removed after they have not been
 699      accessed in 30 days.</para>
 700     </example>
 701
 702     <example>
 703       <title>Empty the contents of a cache directory on boot</title>
 704
 705       <programlisting># /usr/lib/tmpfiles.d/krb5rcache.conf
 706 e! /var/cache/krb5rcache - - - 0
 707 </programlisting>
 708
 709       <para>Any files and subdirectories in <filename>/var/cache/krb5rcache/</filename>
 710       will be removed on boot. The directory will not be created.
 711       </para>
 712     </example>
 713   </refsect1>
 714
 715   <refsect1>
 716     <title>See Also</title>
 717     <para>
 718       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 719       <citerefentry><refentrytitle>systemd-tmpfiles</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 720       <citerefentry><refentrytitle>systemd-delta</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 721       <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 722       <citerefentry project='man-pages'><refentrytitle>attr</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 723       <citerefentry project='man-pages'><refentrytitle>getfattr</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 724       <citerefentry project='man-pages'><refentrytitle>setfattr</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 725       <citerefentry project='man-pages'><refentrytitle>setfacl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 726       <citerefentry project='man-pages'><refentrytitle>getfacl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 727       <citerefentry project='man-pages'><refentrytitle>chattr</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 728       <citerefentry project='die-net'><refentrytitle>btrfs-subvolume</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 729       <citerefentry project='die-net'><refentrytitle>btrfs-qgroup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 730     </para>
 731   </refsect1>
 732
 733 </refentry>