man/repart.d.xml

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   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
   6   <refentryinfo>
   7     <title>repart.d</title>
   8     <productname>systemd</productname>
   9   </refentryinfo>
  10
  11   <refmeta>
  12     <refentrytitle>repart.d</refentrytitle>
  13     <manvolnum>5</manvolnum>
  14   </refmeta>
  15
  16   <refnamediv>
  17     <refname>repart.d</refname>
  18     <refpurpose>Partition Definition Files for Automatic Boot-Time Repartitioning</refpurpose>
  19   </refnamediv>
  20
  21   <refsynopsisdiv>
  22     <para><literallayout><filename>/etc/repart.d/*.conf</filename>
  23 <filename>/run/repart.d/*.conf</filename>
  24 <filename>/usr/lib/repart.d/*.conf</filename>
  25     </literallayout></para>
  26   </refsynopsisdiv>
  27
  28   <refsect1>
  29     <title>Description</title>
  30
  31     <para><filename>repart.d/*.conf</filename> files describe basic properties of partitions of block
  32     devices of the local system. They may be used to declare types, names and sizes of partitions that shall
  33     exist. The
  34     <citerefentry><refentrytitle>systemd-repart</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  35     service reads these files and attempts to add new partitions currently missing and enlarge existing
  36     partitions according to these definitions. Operation is generally incremental, i.e. when applied, what
  37     exists already is left intact, and partitions are never shrunk, moved or deleted.</para>
  38
  39     <para>These definition files are useful for implementing operating system images that are prepared and
  40     delivered with minimally sized images (for example lacking any state or swap partitions), and which on
  41     first boot automatically take possession of any remaining disk space following a few basic rules.</para>
  42
  43     <para>Currently, support for partition definition files is only implemented for GPT partitition
  44     tables.</para>
  45
  46     <para>Partition files are generally matched against any partitions already existing on disk in a simple
  47     algorithm: the partition files are sorted by their filename (ignoring the directory prefix), and then
  48     compared in order against existing partitions matching the same partition type UUID. Specifically, the
  49     first existing partition with a specific partition type UUID is assigned the first definition file with
  50     the same partition type UUID, and the second existing partition with a specific type UUID the second
  51     partition file with the same type UUID, and so on. Any left-over partition files that have no matching
  52     existing partition are assumed to define new partition that shall be created. Such partitions are
  53     appended to the end of the partition table, in the order defined by their names utilizing the first
  54     partition slot greater than the highest slot number currently in use. Any existing partitions that have
  55     no matching partition file are left as they are.</para>
  56
  57     <para>Note that these partition definition files do not describe the contents of the partitions, such as
  58     the file system used. Separate mechanisms, such as
  59     <citerefentry><refentrytitle>systemd-growfs</refentrytitle><manvolnum>8</manvolnum></citerefentry> and
  60     <command>systemd-makefs</command> maybe be used to initialize or grow the file systems inside of these
  61     partitions.</para>
  62   </refsect1>
  63
  64   <refsect1>
  65     <title>[Partition] Section Options</title>
  66
  67     <variablelist>
  68       <varlistentry>
  69         <term><varname>Type=</varname></term>
  70
  71         <listitem><para>The GPT partition type UUID to match. This may be a GPT partition type UUID such as
  72         <constant>4f68bce3-e8cd-4db1-96e7-fbcaf984b709</constant>, or one of the following special
  73         identifiers:</para>
  74
  75         <table>
  76           <title>GPT partition type identifiers</title>
  77
  78           <tgroup cols='2' align='left' colsep='1' rowsep='1'>
  79             <colspec colname="name" />
  80             <colspec colname="explanation" />
  81
  82             <thead>
  83               <row>
  84                 <entry>Identifier</entry>
  85                 <entry>Explanation</entry>
  86               </row>
  87             </thead>
  88
  89             <tbody>
  90               <row>
  91                 <entry><constant>esp</constant></entry>
  92                 <entry>EFI System Partition</entry>
  93               </row>
  94
  95               <row>
  96                 <entry><constant>xbootldr</constant></entry>
  97                 <entry>Extended Boot Loader Partition</entry>
  98               </row>
  99
 100               <row>
 101                 <entry><constant>swap</constant></entry>
 102                 <entry>Swap partition</entry>
 103               </row>
 104
 105               <row>
 106                 <entry><constant>home</constant></entry>
 107                 <entry>Home (<filename>/home/</filename>) partition</entry>
 108               </row>
 109
 110               <row>
 111                 <entry><constant>srv</constant></entry>
 112                 <entry>Server data (<filename>/srv/</filename>) partition</entry>
 113               </row>
 114
 115               <row>
 116                 <entry><constant>var</constant></entry>
 117                 <entry>Variable data (<filename>/var/</filename>) partition</entry>
 118               </row>
 119
 120               <row>
 121                 <entry><constant>tmp</constant></entry>
 122                 <entry>Temporary data (<filename>/var/tmp/</filename>) partition</entry>
 123               </row>
 124
 125               <row>
 126                 <entry><constant>linux-generic</constant></entry>
 127                 <entry>Generic Linux file system partition</entry>
 128               </row>
 129
 130               <row>
 131                 <entry><constant>root</constant></entry>
 132                 <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>
 133               </row>
 134
 135               <row>
 136                 <entry><constant>root-verity</constant></entry>
 137                 <entry>Verity data for the root file system partition for the local architecture</entry>
 138               </row>
 139
 140               <row>
 141                 <entry><constant>root-secondary</constant></entry>
 142                 <entry>Root file system partition of the secondary architecture of the local architecture; usually the matching 32bit architecture for the local 64bit architecture)</entry>
 143               </row>
 144
 145               <row>
 146                 <entry><constant>root-secondary-verity</constant></entry>
 147                 <entry>Verity data for the root file system partition of the secondary architecture</entry>
 148               </row>
 149
 150               <row>
 151                 <entry><constant>root-x86</constant></entry>
 152                 <entry>Root file system partition for the x86 (32bit, aka i386) architecture</entry>
 153               </row>
 154
 155               <row>
 156                 <entry><constant>root-x86-verity</constant></entry>
 157                 <entry>Verity data for the x86 (32bit) root file system partition</entry>
 158               </row>
 159
 160               <row>
 161                 <entry><constant>root-x86-64</constant></entry>
 162                 <entry>Root file system partition for the x86_64 (64bit, aka amd64) architecture</entry>
 163               </row>
 164
 165               <row>
 166                 <entry><constant>root-x86-64-verity</constant></entry>
 167                 <entry>Verity data for the x86_64 (64bit) root file system partition</entry>
 168               </row>
 169
 170               <row>
 171                 <entry><constant>root-arm</constant></entry>
 172                 <entry>Root file system partition for the ARM (32bit) architecture</entry>
 173               </row>
 174
 175               <row>
 176                 <entry><constant>root-arm-verity</constant></entry>
 177                 <entry>Verity data for the ARM (32bit) root file system partition</entry>
 178               </row>
 179
 180               <row>
 181                 <entry><constant>root-arm64</constant></entry>
 182                 <entry>Root file system partition for the ARM (64bit, aka aarch64) architecture</entry>
 183               </row>
 184
 185               <row>
 186                 <entry><constant>root-arm64-verity</constant></entry>
 187                 <entry>Verity data for the ARM (64bit, aka aarch64) root file system partition</entry>
 188               </row>
 189
 190               <row>
 191                 <entry><constant>root-ia64</constant></entry>
 192                 <entry>Root file system partition for the ia64 architecture</entry>
 193               </row>
 194
 195               <row>
 196                 <entry><constant>root-ia64-verity</constant></entry>
 197                 <entry>Verity data for the ia64 root file system partition</entry>
 198               </row>
 199             </tbody>
 200           </tgroup>
 201         </table>
 202
 203         <para>This setting defaults to <constant>linux-generic</constant>.</para>
 204
 205         <para>Most of the partition type UUIDs listed above are defined in the <ulink
 206         url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions
 207         Specification</ulink>.</para></listitem>
 208       </varlistentry>
 209
 210       <varlistentry>
 211         <term><varname>Label=</varname></term>
 212
 213         <listitem><para>The textual label to assign to the partition if none is assigned yet. Note that this
 214         setting is not used for matching. It is also not used when a label is already set for an existing
 215         partition. It is thus only used when a partition is newly created or when an existing one had a no
 216         label set (that is: an empty label). If not specified a label derived from the partition type is
 217         automatically used.</para></listitem>
 218       </varlistentry>
 219
 220       <varlistentry>
 221         <term><varname>Priority=</varname></term>
 222
 223         <listitem><para>A numeric priority to assign to this partition, in the range -2147483648…2147483647,
 224         with smaller values indicating higher priority, and higher values indicating smaller priority. This
 225         priority is used in case the configured size constraints on the defined partitions do not permit
 226         fitting all partitions onto the available disk space. If the partitions do not fit, the highest
 227         numeric partition priority of all defined partitions is determined, and all defined partitions with
 228         this priority are removed from the list of new partitions to create (which may be multiple, if the
 229         same priority is used for multiple partitions). The fitting algorithm is then tried again. If the
 230         partitions still do not fit, the now highest numeric partition priority is determined, and the
 231         matching partitions removed too, and so on. Partitions of a priority of 0 or lower are never
 232         removed. If all partitions with a priority above 0 are removed and the partitions still do not fit on
 233         the device the operation fails. Note that this priority has no effect on ordering partitions, for
 234         that use the alphabetical order of the filenames of the partition definition files. Defaults to
 235         0.</para></listitem>
 236       </varlistentry>
 237
 238       <varlistentry>
 239         <term><varname>Weight=</varname></term>
 240
 241         <listitem><para>A numeric weight to assign to this partition in the range 0…1000000. Available disk
 242         space is assigned the defined partitions according to their relative weights (subject to the size
 243         constraints configured with <varname>SizeMinBytes=</varname>, <varname>SizeMaxBytes=</varname>), so
 244         that a partition with weight 2000 gets double the space as one with weight 1000, and a partition with
 245         weight 333 a third of that. Defaults to 1000.</para>
 246
 247         <para>The <varname>Weight=</varname> setting is used to distribute available disk space in an
 248         "elastic" fashion, based on the disk size and existing partitions. If a partition shall have a fixed
 249         size use both <varname>SizeMinBytes=</varname> and <varname>SizeMaxBytes=</varname> with the same
 250         value in order to fixate the size to one value, in which case the weight has no
 251         effect.</para></listitem>
 252       </varlistentry>
 253
 254       <varlistentry>
 255         <term><varname>PaddingWeight=</varname></term>
 256
 257         <listitem><para>Similar to <varname>Weight=</varname> but sets a weight for the free space after the
 258         partition (the "padding"). When distributing available space the weights of all partitions and all
 259         defined padding is summed, and then each partition and padding gets the fraction defined by its
 260         weight. Defaults to 0, i.e. by default no padding is applied.</para>
 261
 262         <para>Padding is useful if empty space shall be left for later additions or a safety margin at the
 263         end of the device or between partitions.</para></listitem>
 264       </varlistentry>
 265
 266       <varlistentry>
 267         <term><varname>SizeMinBytes=</varname></term>
 268         <term><varname>SizeMaxBytes=</varname></term>
 269
 270         <listitem><para>Specifies minimum and maximum size constraints in bytes. Takes the usual K, M, G, T,
 271         …  suffixes (to the base of 1024). If <varname>SizeMinBytes=</varname> is specified the partition is
 272         created at or grown to at least the specified size. If <varname>SizeMaxBytes=</varname> is specified
 273         the partition is created at or grown to at most the specified size. The precise size is determined
 274         through the weight value value configured with <varname>Weight=</varname>, see above. When
 275         <varname>SizeMinBytes=</varname> is set equal to <varname>SizeMaxBytes=</varname> the configured
 276         weight has no effect as the partition is explicitly sized to the specified fixed value. Note that
 277         partitions are never created smaller than 4096 bytes, and since partitions are never shrunk the
 278         previous size of the partition (in case the partition already exists) is also enforced as lower bound
 279         for the new size. The values should be specified as multiples of 4096 bytes, and are rounded upwards
 280         (in case of <varname>SizeMinBytes=</varname>) or downwards (in case of
 281         <varname>SizeMaxBytes=</varname>) otherwise. If the backing device does not provide enough space to
 282         fulfill the constraints placing the partition will fail. For partitions that shall be created,
 283         depending on the setting of <varname>Priority=</varname> (see above) the partition might be dropped
 284         and the placing algorithm restarted. By default no size constraints are set.</para></listitem>
 285       </varlistentry>
 286
 287       <varlistentry>
 288         <term><varname>PaddingMinBytes=</varname></term>
 289         <term><varname>PaddingMaxBytes=</varname></term>
 290
 291         <listitem><para>Specifies minimum and maximum size constrains in bytes for the free space after the
 292         partition (the "padding"). Semantics are similar to <varname>SizeMinBytes=</varname> and
 293         <varname>SizeMaxBytes=</varname>, except that unlike partition sizes free space can be shrunk and can
 294         be as small as zero. By default no size constraints on padding are set, so that only
 295         <varname>PaddingWeight=</varname> determines the size of the padding applied.</para></listitem>
 296       </varlistentry>
 297
 298       <varlistentry>
 299         <term><varname>FactoryReset=</varname></term>
 300
 301         <listitem><para>Takes a boolean argument. If specified the partition is marked for removal during a
 302         factory reset operation. This functionality is useful to implement schemes where images can be reset
 303         into their original state by removing partitions and creating them anew. Defaults to off.</para></listitem>
 304       </varlistentry>
 305     </variablelist>
 306   </refsect1>
 307
 308   <refsect1>
 309     <title>Examples</title>
 310
 311     <example>
 312       <title>Grow the root partition to the full disk size at first boot</title>
 313
 314       <para>With the following file the root partition is automatically grown to the full disk if possible during boot.</para>
 315
 316       <para><programlisting># /usr/lib/repart.d/50-root.conf
 317 [Partition]
 318 Type=root
 319 </programlisting></para>
 320     </example>
 321
 322     <example>
 323       <title>Create a swap and home partition automatically on boot, if missing</title>
 324
 325       <para>The home partition gets all available disk space while the swap partition gets 1G at most and 64M
 326       at least. We set a priority > 0 on the swap partition to ensure the swap partition is not used if not
 327       enough space is available. For every three bytes assigned to the home partition the swap partition gets
 328       assigned one.</para>
 329
 330       <para><programlisting># /usr/lib/repart.d/60-home.conf
 331 [Partition]
 332 Type=home
 333 </programlisting></para>
 334
 335       <para><programlisting># /usr/lib/repart.d/70-swap.conf
 336 [Partition]
 337 Type=swap
 338 SizeMinBytes=64M
 339 SizeMaxBytes=1G
 340 Priority=1
 341 Weight=333
 342 </programlisting></para>
 343     </example>
 344
 345     <example>
 346       <title>Create B partitions in an A/B Verity setup, if missing</title>
 347
 348       <para>Let's say the vendor intends to update OS images in an A/B setup, i.e. with two root partitions
 349       (and two matching Verity partitions) that shall be used alternatingly during upgrades. To minimize
 350       image sizes the original image is shipped only with one root and one Verity partition (the "A" set),
 351       and the second root and Verity partitions (the "B" set) shall be created on first boot on the free
 352       space on the medium.</para>
 353
 354       <para><programlisting># /usr/lib/repart.d/50-root.conf
 355 [Partition]
 356 Type=root
 357 SizeMinBytes=512M
 358 SizeMaxBytes=512M
 359 </programlisting></para>
 360
 361       <para><programlisting># /usr/lib/repart.d/60-root-verity.conf
 362 [Partition]
 363 Type=root-verity
 364 SizeMinBytes=64M
 365 SizeMaxBytes=64M
 366 </programlisting></para>
 367
 368       <para>The definitions above cover the "A" set of root partition (of a fixed 512M size) and Verity
 369       partition for the root partition (of a fixed 64M size). Let's use symlinks to create the "B" set of
 370       partitions, since after all they shall have the same properties and sizes as the "A" set.</para>
 371
 372 <para><programlisting># ln -s 50-root.conf /usr/lib/repart.d/70-root-b.conf
 373 # ln -s 60-root-verity.conf /usr/lib/repart.d/80-root-verity-b.conf
 374 </programlisting></para>
 375     </example>
 376
 377   </refsect1>
 378
 379   <refsect1>
 380     <title>See Also</title>
 381     <para>
 382       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 383       <citerefentry><refentrytitle>systemd-repart</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 384       <citerefentry project='man-pages'><refentrytitle>sfdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 385     </para>
 386   </refsect1>
 387
 388 </refentry>