man/repart.d.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <refentry id="repart.d" conditional='ENABLE_REPART'
   5           xmlns:xi="http://www.w3.org/2001/XInclude">
   6
   7   <refentryinfo>
   8     <title>repart.d</title>
   9     <productname>systemd</productname>
  10   </refentryinfo>
  11
  12   <refmeta>
  13     <refentrytitle>repart.d</refentrytitle>
  14     <manvolnum>5</manvolnum>
  15   </refmeta>
  16
  17   <refnamediv>
  18     <refname>repart.d</refname>
  19     <refpurpose>Partition Definition Files for Automatic Boot-Time Repartitioning</refpurpose>
  20   </refnamediv>
  21
  22   <refsynopsisdiv>
  23     <para><literallayout><filename>/etc/repart.d/*.conf</filename>
  24 <filename>/run/repart.d/*.conf</filename>
  25 <filename>/usr/lib/repart.d/*.conf</filename>
  26     </literallayout></para>
  27   </refsynopsisdiv>
  28
  29   <refsect1>
  30     <title>Description</title>
  31
  32     <para><filename>repart.d/*.conf</filename> files describe basic properties of partitions of block
  33     devices of the local system. They may be used to declare types, names and sizes of partitions that shall
  34     exist. The
  35     <citerefentry><refentrytitle>systemd-repart</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  36     service reads these files and attempts to add new partitions currently missing and enlarge existing
  37     partitions according to these definitions. Operation is generally incremental, i.e. when applied, what
  38     exists already is left intact, and partitions are never shrunk, moved or deleted.</para>
  39
  40     <para>These definition files are useful for implementing operating system images that are prepared and
  41     delivered with minimally sized images (for example lacking any state or swap partitions), and which on
  42     first boot automatically take possession of any remaining disk space following a few basic rules.</para>
  43
  44     <para>Currently, support for partition definition files is only implemented for GPT partitition
  45     tables.</para>
  46
  47     <para>Partition files are generally matched against any partitions already existing on disk in a simple
  48     algorithm: the partition files are sorted by their filename (ignoring the directory prefix), and then
  49     compared in order against existing partitions matching the same partition type UUID. Specifically, the
  50     first existing partition with a specific partition type UUID is assigned the first definition file with
  51     the same partition type UUID, and the second existing partition with a specific type UUID the second
  52     partition file with the same type UUID, and so on. Any left-over partition files that have no matching
  53     existing partition are assumed to define new partition that shall be created. Such partitions are
  54     appended to the end of the partition table, in the order defined by their names utilizing the first
  55     partition slot greater than the highest slot number currently in use. Any existing partitions that have
  56     no matching partition file are left as they are.</para>
  57
  58     <para>Note that these definitions may only be used to created and initialize new partitions or grow
  59     existing ones. In the latter case it will not grow the contained files systems however; separate
  60     mechanisms, such as
  61     <citerefentry><refentrytitle>systemd-growfs</refentrytitle><manvolnum>8</manvolnum></citerefentry> may be
  62     used to grow the file systems inside of these partitions.</para>
  63   </refsect1>
  64
  65   <refsect1>
  66     <title>[Partition] Section Options</title>
  67
  68     <variablelist>
  69       <varlistentry>
  70         <term><varname>Type=</varname></term>
  71
  72         <listitem><para>The GPT partition type UUID to match. This may be a GPT partition type UUID such as
  73         <constant>4f68bce3-e8cd-4db1-96e7-fbcaf984b709</constant>, or one of the following special
  74         identifiers:</para>
  75
  76         <table>
  77           <title>GPT partition type identifiers</title>
  78
  79           <tgroup cols='2' align='left' colsep='1' rowsep='1'>
  80             <colspec colname="name" />
  81             <colspec colname="explanation" />
  82
  83             <thead>
  84               <row>
  85                 <entry>Identifier</entry>
  86                 <entry>Explanation</entry>
  87               </row>
  88             </thead>
  89
  90             <tbody>
  91               <row>
  92                 <entry><constant>esp</constant></entry>
  93                 <entry>EFI System Partition</entry>
  94               </row>
  95
  96               <row>
  97                 <entry><constant>xbootldr</constant></entry>
  98                 <entry>Extended Boot Loader Partition</entry>
  99               </row>
 100
 101               <row>
 102                 <entry><constant>swap</constant></entry>
 103                 <entry>Swap partition</entry>
 104               </row>
 105
 106               <row>
 107                 <entry><constant>home</constant></entry>
 108                 <entry>Home (<filename>/home/</filename>) partition</entry>
 109               </row>
 110
 111               <row>
 112                 <entry><constant>srv</constant></entry>
 113                 <entry>Server data (<filename>/srv/</filename>) partition</entry>
 114               </row>
 115
 116               <row>
 117                 <entry><constant>var</constant></entry>
 118                 <entry>Variable data (<filename>/var/</filename>) partition</entry>
 119               </row>
 120
 121               <row>
 122                 <entry><constant>tmp</constant></entry>
 123                 <entry>Temporary data (<filename>/var/tmp/</filename>) partition</entry>
 124               </row>
 125
 126               <row>
 127                 <entry><constant>linux-generic</constant></entry>
 128                 <entry>Generic Linux file system partition</entry>
 129               </row>
 130
 131               <row>
 132                 <entry><constant>root</constant></entry>
 133                 <entry>Root file system partition type appropriate for the local architecture (an alias for an architecture root file system partition type listed below, e.g. <constant>root-x86-64</constant>)</entry>
 134               </row>
 135
 136               <row>
 137                 <entry><constant>root-verity</constant></entry>
 138                 <entry>Verity data for the root file system partition for the local architecture</entry>
 139               </row>
 140
 141               <row>
 142                 <entry><constant>root-secondary</constant></entry>
 143                 <entry>Root file system partition of the secondary architecture of the local architecture (usually the matching 32bit architecture for the local 64bit architecture)</entry>
 144               </row>
 145
 146               <row>
 147                 <entry><constant>root-secondary-verity</constant></entry>
 148                 <entry>Verity data for the root file system partition of the secondary architecture</entry>
 149               </row>
 150
 151               <row>
 152                 <entry><constant>root-x86</constant></entry>
 153                 <entry>Root file system partition for the x86 (32bit, aka i386) architecture</entry>
 154               </row>
 155
 156               <row>
 157                 <entry><constant>root-x86-verity</constant></entry>
 158                 <entry>Verity data for the x86 (32bit) root file system partition</entry>
 159               </row>
 160
 161               <row>
 162                 <entry><constant>root-x86-64</constant></entry>
 163                 <entry>Root file system partition for the x86_64 (64bit, aka amd64) architecture</entry>
 164               </row>
 165
 166               <row>
 167                 <entry><constant>root-x86-64-verity</constant></entry>
 168                 <entry>Verity data for the x86_64 (64bit) root file system partition</entry>
 169               </row>
 170
 171               <row>
 172                 <entry><constant>root-arm</constant></entry>
 173                 <entry>Root file system partition for the ARM (32bit) architecture</entry>
 174               </row>
 175
 176               <row>
 177                 <entry><constant>root-arm-verity</constant></entry>
 178                 <entry>Verity data for the ARM (32bit) root file system partition</entry>
 179               </row>
 180
 181               <row>
 182                 <entry><constant>root-arm64</constant></entry>
 183                 <entry>Root file system partition for the ARM (64bit, aka aarch64) architecture</entry>
 184               </row>
 185
 186               <row>
 187                 <entry><constant>root-arm64-verity</constant></entry>
 188                 <entry>Verity data for the ARM (64bit, aka aarch64) root file system partition</entry>
 189               </row>
 190
 191               <row>
 192                 <entry><constant>root-ia64</constant></entry>
 193                 <entry>Root file system partition for the ia64 architecture</entry>
 194               </row>
 195
 196               <row>
 197                 <entry><constant>root-ia64-verity</constant></entry>
 198                 <entry>Verity data for the ia64 root file system partition</entry>
 199               </row>
 200             </tbody>
 201           </tgroup>
 202         </table>
 203
 204         <para>This setting defaults to <constant>linux-generic</constant>.</para>
 205
 206         <para>Most of the partition type UUIDs listed above are defined in the <ulink
 207         url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions
 208         Specification</ulink>.</para></listitem>
 209       </varlistentry>
 210
 211       <varlistentry>
 212         <term><varname>Label=</varname></term>
 213
 214         <listitem><para>The textual label to assign to the partition if none is assigned yet. Note that this
 215         setting is not used for matching. It is also not used when a label is already set for an existing
 216         partition. It is thus only used when a partition is newly created or when an existing one had a no
 217         label set (that is: an empty label). If not specified a label derived from the partition type is
 218         automatically used. Simple specifier expansion is supported, see below.</para></listitem>
 219       </varlistentry>
 220
 221       <varlistentry>
 222         <term><varname>UUID=</varname></term>
 223
 224         <listitem><para>The UUID to assign to the partition if none is assigned yet. Note that this
 225         setting is not used for matching. It is also not used when a UUID is already set for an existing
 226         partition. It is thus only used when a partition is newly created or when an existing one had a
 227         all-zero UUID set. If not specified a UUID derived from the partition type is automatically
 228         used.</para></listitem>
 229       </varlistentry>
 230
 231       <varlistentry>
 232         <term><varname>Priority=</varname></term>
 233
 234         <listitem><para>A numeric priority to assign to this partition, in the range -2147483648…2147483647,
 235         with smaller values indicating higher priority, and higher values indicating smaller priority. This
 236         priority is used in case the configured size constraints on the defined partitions do not permit
 237         fitting all partitions onto the available disk space. If the partitions do not fit, the highest
 238         numeric partition priority of all defined partitions is determined, and all defined partitions with
 239         this priority are removed from the list of new partitions to create (which may be multiple, if the
 240         same priority is used for multiple partitions). The fitting algorithm is then tried again. If the
 241         partitions still do not fit, the now highest numeric partition priority is determined, and the
 242         matching partitions removed too, and so on. Partitions of a priority of 0 or lower are never
 243         removed. If all partitions with a priority above 0 are removed and the partitions still do not fit on
 244         the device the operation fails. Note that this priority has no effect on ordering partitions, for
 245         that use the alphabetical order of the filenames of the partition definition files. Defaults to
 246         0.</para></listitem>
 247       </varlistentry>
 248
 249       <varlistentry>
 250         <term><varname>Weight=</varname></term>
 251
 252         <listitem><para>A numeric weight to assign to this partition in the range 0…1000000. Available disk
 253         space is assigned the defined partitions according to their relative weights (subject to the size
 254         constraints configured with <varname>SizeMinBytes=</varname>, <varname>SizeMaxBytes=</varname>), so
 255         that a partition with weight 2000 gets double the space as one with weight 1000, and a partition with
 256         weight 333 a third of that. Defaults to 1000.</para>
 257
 258         <para>The <varname>Weight=</varname> setting is used to distribute available disk space in an
 259         "elastic" fashion, based on the disk size and existing partitions. If a partition shall have a fixed
 260         size use both <varname>SizeMinBytes=</varname> and <varname>SizeMaxBytes=</varname> with the same
 261         value in order to fixate the size to one value, in which case the weight has no
 262         effect.</para></listitem>
 263       </varlistentry>
 264
 265       <varlistentry>
 266         <term><varname>PaddingWeight=</varname></term>
 267
 268         <listitem><para>Similar to <varname>Weight=</varname> but sets a weight for the free space after the
 269         partition (the "padding"). When distributing available space the weights of all partitions and all
 270         defined padding is summed, and then each partition and padding gets the fraction defined by its
 271         weight. Defaults to 0, i.e. by default no padding is applied.</para>
 272
 273         <para>Padding is useful if empty space shall be left for later additions or a safety margin at the
 274         end of the device or between partitions.</para></listitem>
 275       </varlistentry>
 276
 277       <varlistentry>
 278         <term><varname>SizeMinBytes=</varname></term>
 279         <term><varname>SizeMaxBytes=</varname></term>
 280
 281         <listitem><para>Specifies minimum and maximum size constraints in bytes. Takes the usual K, M, G, T,
 282         …  suffixes (to the base of 1024). If <varname>SizeMinBytes=</varname> is specified the partition is
 283         created at or grown to at least the specified size. If <varname>SizeMaxBytes=</varname> is specified
 284         the partition is created at or grown to at most the specified size. The precise size is determined
 285         through the weight value value configured with <varname>Weight=</varname>, see above. When
 286         <varname>SizeMinBytes=</varname> is set equal to <varname>SizeMaxBytes=</varname> the configured
 287         weight has no effect as the partition is explicitly sized to the specified fixed value. Note that
 288         partitions are never created smaller than 4096 bytes, and since partitions are never shrunk the
 289         previous size of the partition (in case the partition already exists) is also enforced as lower bound
 290         for the new size. The values should be specified as multiples of 4096 bytes, and are rounded upwards
 291         (in case of <varname>SizeMinBytes=</varname>) or downwards (in case of
 292         <varname>SizeMaxBytes=</varname>) otherwise. If the backing device does not provide enough space to
 293         fulfill the constraints placing the partition will fail. For partitions that shall be created,
 294         depending on the setting of <varname>Priority=</varname> (see above) the partition might be dropped
 295         and the placing algorithm restarted. By default a minimum size constraint of 10M and no maximum size
 296         constraint is set.</para></listitem>
 297       </varlistentry>
 298
 299       <varlistentry>
 300         <term><varname>PaddingMinBytes=</varname></term>
 301         <term><varname>PaddingMaxBytes=</varname></term>
 302
 303         <listitem><para>Specifies minimum and maximum size constraints in bytes for the free space after the
 304         partition (the "padding"). Semantics are similar to <varname>SizeMinBytes=</varname> and
 305         <varname>SizeMaxBytes=</varname>, except that unlike partition sizes free space can be shrunk and can
 306         be as small as zero. By default no size constraints on padding are set, so that only
 307         <varname>PaddingWeight=</varname> determines the size of the padding applied.</para></listitem>
 308       </varlistentry>
 309
 310       <varlistentry>
 311         <term><varname>CopyBlocks=</varname></term>
 312
 313         <listitem><para>Takes a path to a regular file, block device node or directory. If specified and the
 314         partition is newly created the data from the specified path is written to the newly created
 315         partition, on the block level. If a directory is specified the backing block device of the file
 316         system the directory is on is determined and the data read directly from that. This option is useful
 317         to efficiently replicate existing file systems on the block level on a new partition, for example to
 318         build a simple OS installer or OS image builder.</para>
 319
 320         <para>The file specified here must have a size that is a multiple of the basic block size 512 and not
 321         be empty. If this option is used, the size allocation algorithm is slightly altered: the partition is
 322         created as least as big as required to fit the data in, i.e. the data size is an additional minimum
 323         size value taken into consideration for the allocation algorithm, similar to and in addition to the
 324         <varname>SizeMin=</varname> value configured above.</para>
 325
 326         <para>This option has no effect if the partition it is declared for already exists, i.e. existing
 327         data is never overwritten. Note that the data is copied in before the partition table is updated,
 328         i.e. before the partition actually is persistently created. This provides robustness: it is
 329         guaranteed that the partition either doesn't exist or exists fully populated; it is not possible that
 330         the partition exists but is not or only partially populated.</para>
 331
 332         <para>This option cannot be combined with <varname>Format=</varname> or
 333         <varname>CopyFiles=</varname>.</para></listitem>
 334       </varlistentry>
 335
 336       <varlistentry>
 337         <term><varname>Format=</varname></term>
 338
 339         <listitem><para>Takes a file system name, such as <literal>ext4</literal>, <literal>btrfs</literal>,
 340         <literal>xfs</literal> or <literal>vfat</literal>, or the special value <literal>swap</literal>. If
 341         specified and the partition is newly created it is formatted with the specified file system (or as
 342         swap device). The file system UUID and label are automatically derived from the partition UUID and
 343         label. If this option is used, the size allocation algorithm is slightly altered: the partition is
 344         created as least as big as required for the minimal file system of the specified type (or 4KiB if the
 345         minimal size is not known).</para>
 346
 347         <para>This option has no effect if the partition already exists.</para>
 348
 349         <para>Similar to the behaviour of <varname>CopyBlocks=</varname> the file system is formatted before
 350         the partition is created, ensuring that the partition only ever exists with a fully initialized
 351         file system.</para>
 352
 353         <para>This option cannot be combined with <varname>CopyBlocks=</varname>.</para></listitem>
 354       </varlistentry>
 355
 356       <varlistentry>
 357         <term><varname>CopyFiles=</varname></term>
 358
 359         <listitem><para>Takes a pair of colon separated absolute file system paths. The first path refers to
 360         a source file or directory on the host, the second path refers to a target in the file system of the
 361         newly created partition and formatted file system. This setting may be used to copy files or
 362         directories from the host into the file system that is created due to the <varname>Format=</varname>
 363         option. If <varname>CopyFiles=</varname> is used without <varname>Format=</varname> specified
 364         explicitly, <literal>Format=</literal> with a suitable default is implied (currently
 365         <literal>ext4</literal>, but this may change in the future). This option may be used multiple times
 366         to copy multiple files or directories from host into the newly formatted file system. The colon and
 367         second path may be omitted in which case the source path is also used as the target path (relative to
 368         the root of the newly created file system). If the source path refers to a directory it is copied
 369         recursively.</para>
 370
 371         <para>This option has no effect if the partition already exists: it cannot be used to copy additional
 372         files into an existing partition, it may only be used to populate a file system created anew.</para>
 373
 374         <para>The copy operation is executed before the file system is registered in the partition table,
 375         thus ensuring that a file system populated this way only ever exists fully initialized.</para>
 376
 377         <para>This option cannot be combined with <varname>CopyBlocks=</varname>.</para></listitem>
 378       </varlistentry>
 379
 380       <varlistentry>
 381         <term><varname>Encrypt=</varname></term>
 382
 383         <listitem><para>Takes a boolean parameter, defaulting to false. If true the partition will be
 384         formatted with a LUKS2 superblock, before the blocks configured with <varname>CopyBlocks=</varname>
 385         are copied in or the file system configured with <varname>Format=</varname> is created.</para>
 386
 387         <para>The LUKS2 UUID is automatically derived from the partition UUID in a stable fashion. A single
 388         key is added to the LUKS2 superblock, configurable with the <option>--key-file=</option> switch to
 389         <command>systemd-repart</command>.</para>
 390
 391         <para>When used this slightly alters the size allocation logic as the implicit, minimal size limits
 392         of <varname>Format=</varname> and <varname>CopyBlocks=</varname> are increased by the space necessary
 393         for the LUKS2 superblock (see above).</para>
 394
 395         <para>This option has no effect if the partition already exists.</para></listitem>
 396       </varlistentry>
 397
 398       <varlistentry>
 399         <term><varname>FactoryReset=</varname></term>
 400
 401         <listitem><para>Takes a boolean argument. If specified the partition is marked for removal during a
 402         factory reset operation. This functionality is useful to implement schemes where images can be reset
 403         into their original state by removing partitions and creating them anew. Defaults to off.</para></listitem>
 404       </varlistentry>
 405     </variablelist>
 406   </refsect1>
 407
 408   <refsect1>
 409     <title>Specifiers</title>
 410
 411     <para>Specifiers may be used in the <varname>Label=</varname> setting. The following expansions are understood:</para>
 412       <table class='specifiers'>
 413         <title>Specifiers available</title>
 414         <tgroup cols='3' align='left' colsep='1' rowsep='1'>
 415           <colspec colname="spec" />
 416           <colspec colname="mean" />
 417           <colspec colname="detail" />
 418           <thead>
 419             <row>
 420               <entry>Specifier</entry>
 421               <entry>Meaning</entry>
 422               <entry>Details</entry>
 423             </row>
 424           </thead>
 425           <tbody>
 426             <xi:include href="standard-specifiers.xml" xpointer="a"/>
 427             <xi:include href="standard-specifiers.xml" xpointer="b"/>
 428             <xi:include href="standard-specifiers.xml" xpointer="B"/>
 429             <xi:include href="standard-specifiers.xml" xpointer="H"/>
 430             <xi:include href="standard-specifiers.xml" xpointer="l"/>
 431             <xi:include href="standard-specifiers.xml" xpointer="m"/>
 432             <xi:include href="standard-specifiers.xml" xpointer="o"/>
 433             <xi:include href="standard-specifiers.xml" xpointer="v"/>
 434             <xi:include href="standard-specifiers.xml" xpointer="w"/>
 435             <xi:include href="standard-specifiers.xml" xpointer="W"/>
 436             <xi:include href="standard-specifiers.xml" xpointer="percent"/>
 437           </tbody>
 438         </tgroup>
 439       </table>
 440   </refsect1>
 441
 442   <refsect1>
 443     <title>Examples</title>
 444
 445     <example>
 446       <title>Grow the root partition to the full disk size at first boot</title>
 447
 448       <para>With the following file the root partition is automatically grown to the full disk if possible during boot.</para>
 449
 450       <para><programlisting># /usr/lib/repart.d/50-root.conf
 451 [Partition]
 452 Type=root
 453 </programlisting></para>
 454     </example>
 455
 456     <example>
 457       <title>Create a swap and home partition automatically on boot, if missing</title>
 458
 459       <para>The home partition gets all available disk space while the swap partition gets 1G at most and 64M
 460       at least. We set a priority > 0 on the swap partition to ensure the swap partition is not used if not
 461       enough space is available. For every three bytes assigned to the home partition the swap partition gets
 462       assigned one.</para>
 463
 464       <para><programlisting># /usr/lib/repart.d/60-home.conf
 465 [Partition]
 466 Type=home
 467 </programlisting></para>
 468
 469       <para><programlisting># /usr/lib/repart.d/70-swap.conf
 470 [Partition]
 471 Type=swap
 472 SizeMinBytes=64M
 473 SizeMaxBytes=1G
 474 Priority=1
 475 Weight=333
 476 </programlisting></para>
 477     </example>
 478
 479     <example>
 480       <title>Create B partitions in an A/B Verity setup, if missing</title>
 481
 482       <para>Let's say the vendor intends to update OS images in an A/B setup, i.e. with two root partitions
 483       (and two matching Verity partitions) that shall be used alternatingly during upgrades. To minimize
 484       image sizes the original image is shipped only with one root and one Verity partition (the "A" set),
 485       and the second root and Verity partitions (the "B" set) shall be created on first boot on the free
 486       space on the medium.</para>
 487
 488       <para><programlisting># /usr/lib/repart.d/50-root.conf
 489 [Partition]
 490 Type=root
 491 SizeMinBytes=512M
 492 SizeMaxBytes=512M
 493 </programlisting></para>
 494
 495       <para><programlisting># /usr/lib/repart.d/60-root-verity.conf
 496 [Partition]
 497 Type=root-verity
 498 SizeMinBytes=64M
 499 SizeMaxBytes=64M
 500 </programlisting></para>
 501
 502       <para>The definitions above cover the "A" set of root partition (of a fixed 512M size) and Verity
 503       partition for the root partition (of a fixed 64M size). Let's use symlinks to create the "B" set of
 504       partitions, since after all they shall have the same properties and sizes as the "A" set.</para>
 505
 506 <para><programlisting># ln -s 50-root.conf /usr/lib/repart.d/70-root-b.conf
 507 # ln -s 60-root-verity.conf /usr/lib/repart.d/80-root-verity-b.conf
 508 </programlisting></para>
 509     </example>
 510
 511   </refsect1>
 512
 513   <refsect1>
 514     <title>See Also</title>
 515     <para>
 516       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 517       <citerefentry><refentrytitle>systemd-repart</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 518       <citerefentry project='man-pages'><refentrytitle>sfdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 519     </para>
 520   </refsect1>
 521
 522 </refentry>