man/systemd-boot.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="systemd-boot" conditional='ENABLE_EFI'
   7     xmlns:xi="http://www.w3.org/2001/XInclude">
   8   <refentryinfo>
   9     <title>systemd-boot</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>systemd-boot</refentrytitle>
  15     <manvolnum>7</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>systemd-boot</refname>
  20     <refname>sd-boot</refname>
  21     <refpurpose>A simple UEFI boot manager</refpurpose>
  22   </refnamediv>
  23
  24   <refsect1>
  25     <title>Description</title>
  26
  27     <para><command>systemd-boot</command> (short: <command>sd-boot</command>) is a simple UEFI boot
  28     manager. It provides a graphical menu to select the entry to boot and an editor for the kernel command
  29     line. <command>systemd-boot</command> supports systems with UEFI firmware only.</para>
  30
  31     <para><command>systemd-boot</command> loads boot entry information from the EFI system partition (ESP),
  32     usually mounted at <filename>/efi/</filename>, <filename>/boot/</filename>, or
  33     <filename>/boot/efi/</filename> during OS runtime, as well as from the Extended Boot Loader partition if
  34     it exists (usually mounted to <filename>/boot/</filename>). Configuration file fragments, kernels,
  35     initrds and other EFI images to boot generally need to reside on the ESP or the Extended Boot Loader
  36     partition. Linux kernels must be built with <option>CONFIG_EFI_STUB</option> to be able to be directly
  37     executed as an EFI image. During boot <command>systemd-boot</command> automatically assembles a list of
  38     boot entries from the following sources:</para>
  39
  40     <itemizedlist>
  41       <listitem><para>Boot entries defined with <ulink
  42       url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink> description files
  43       located in <filename>/loader/entries/</filename> on the ESP and the Extended Boot Loader
  44       Partition. These usually describe Linux kernel images with associated initrd images, but alternatively
  45       may also describe arbitrary other EFI executables.</para></listitem>
  46
  47       <listitem><para>Unified kernel images following the <ulink
  48       url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink>, as executable EFI
  49       binaries in <filename>/EFI/Linux/</filename> on the ESP and the Extended Boot Loader Partition.
  50       </para></listitem>
  51
  52       <listitem><para>The Microsoft Windows EFI boot manager, if installed</para></listitem>
  53
  54       <listitem><para>The Apple MacOS X boot manager, if installed</para></listitem>
  55
  56       <listitem><para>The EFI Shell binary, if installed</para></listitem>
  57
  58       <listitem><para>A reboot into the UEFI firmware setup option, if supported by the firmware</para></listitem>
  59     </itemizedlist>
  60
  61     <para><command>systemd-boot</command> supports the following features:</para>
  62
  63     <itemizedlist>
  64       <listitem><para>Basic boot manager configuration changes (such as timeout
  65       configuration, default boot entry selection, …) may be made directly from the boot loader UI at
  66       boot-time, as well as during system runtime with EFI variables.</para></listitem>
  67
  68       <listitem><para>The boot manager integrates with the <command>systemctl</command> command to implement
  69       features such as <command>systemctl reboot --boot-loader-entry=…</command> (for rebooting into a
  70       specific boot menu entry, i.e. "reboot into Windows") and <command>systemctl reboot
  71       --boot-loader-menu=…</command> (for rebooting into the boot loader menu), by implementing the <ulink
  72       url="https://systemd.io/BOOT_LOADER_INTERFACE">Boot Loader Interface</ulink>. See
  73       <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
  74       details.</para></listitem>
  75
  76       <listitem><para>An EFI variable set by the boot loader informs the OS about the ESP partition used
  77       during boot. This is then used to automatically mount the correct ESP partition to
  78       <filename>/efi/</filename> or <filename>/boot/</filename> during OS runtime. See
  79       <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  80       for details.</para></listitem>
  81
  82       <listitem><para>The boot manager provides information about the boot time spent in UEFI firmware using
  83       the <ulink url="https://systemd.io/BOOT_LOADER_INTERFACE">Boot Loader Interface</ulink>. This
  84       information can be displayed using
  85       <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
  86       </para></listitem>
  87
  88       <listitem><para>The boot manager implements boot counting and automatic fallback to older, working boot
  89       entries on failure. See <ulink url="https://systemd.io/AUTOMATIC_BOOT_ASSESSMENT">Automatic Boot
  90       Assessment</ulink>.</para></listitem>
  91
  92       <listitem><para>The boot manager optionally reads a random seed from the ESP partition, combines it
  93       with a 'system token' stored in a persistent EFI variable and derives a random seed to use by the OS as
  94       entropy pool initializaton, providing a full entropy pool during early boot.</para></listitem>
  95     </itemizedlist>
  96
  97     <para><citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  98     may be used from a running system to locate the ESP and the Extended Boot Loader Partition, list
  99     available entries, and install <command>systemd-boot</command> itself.</para>
 100
 101     <para><citerefentry><refentrytitle>kernel-install</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 102     may be used to copy kernel images onto the ESP or the Extended Boot Loader Partition and to generate
 103     description files compliant with the Boot Loader
 104     Specification.</para>
 105   </refsect1>
 106
 107   <refsect1>
 108     <title>Key bindings</title>
 109     <para>The following keys may be used in the boot menu:</para>
 110
 111     <variablelist>
 112       <varlistentry>
 113         <term><keycap>↑</keycap> (Up)</term>
 114         <term><keycap>↓</keycap> (Down)</term>
 115         <term><keycap>j</keycap></term>
 116         <term><keycap>k</keycap></term>
 117         <term><keycap>PageUp</keycap></term>
 118         <term><keycap>PageDown</keycap></term>
 119         <term><keycap>Home</keycap></term>
 120         <term><keycap>End</keycap></term>
 121         <listitem><para>Navigate up/down in the entry list</para></listitem>
 122       </varlistentry>
 123
 124       <varlistentry>
 125         <term><keycap>↵</keycap> (Enter)</term>
 126         <term><keycap>→</keycap> (Right)</term>
 127         <listitem><para>Boot selected entry</para></listitem>
 128       </varlistentry>
 129
 130       <varlistentry>
 131         <term><keycap>d</keycap></term>
 132         <listitem><para>Make selected entry the default</para></listitem>
 133       </varlistentry>
 134
 135       <varlistentry>
 136         <term><keycap>e</keycap></term>
 137         <listitem><para>Edit the kernel command line for selected entry</para></listitem>
 138       </varlistentry>
 139
 140       <varlistentry>
 141         <term><keycap>+</keycap></term>
 142         <term><keycap>t</keycap></term>
 143         <listitem><para>Increase the timeout before default entry is booted</para></listitem>
 144       </varlistentry>
 145
 146       <varlistentry>
 147         <term><keycap>-</keycap></term>
 148         <term><keycap>T</keycap></term>
 149         <listitem><para>Decrease the timeout</para></listitem>
 150       </varlistentry>
 151
 152       <varlistentry>
 153         <term><keycap>v</keycap></term>
 154         <listitem><para>Show systemd-boot, UEFI, and firmware versions</para></listitem>
 155       </varlistentry>
 156
 157       <varlistentry>
 158         <term><keycap>P</keycap></term>
 159         <listitem><para>Print status</para></listitem>
 160       </varlistentry>
 161
 162       <varlistentry>
 163         <term><keycap>Q</keycap></term>
 164         <listitem><para>Quit</para></listitem>
 165       </varlistentry>
 166
 167       <varlistentry>
 168         <term><keycap>h</keycap></term>
 169         <term><keycap>?</keycap></term>
 170         <listitem><para>Show a help screen</para></listitem>
 171       </varlistentry>
 172
 173       <varlistentry>
 174         <term><keycombo><keycap>Ctrl</keycap><keycap>l</keycap></keycombo></term>
 175         <listitem><para>Reprint the screen</para></listitem>
 176       </varlistentry>
 177     </variablelist>
 178
 179     <para>The following keys may be used during bootup or in the boot menu to
 180     directly boot a specific entry:</para>
 181
 182     <variablelist>
 183       <varlistentry>
 184         <term><keycap>l</keycap></term>
 185         <listitem><para>Linux</para></listitem>
 186       </varlistentry>
 187
 188       <varlistentry>
 189         <term><keycap>w</keycap></term>
 190         <listitem><para>Windows</para></listitem>
 191       </varlistentry>
 192
 193       <varlistentry>
 194         <term><keycap>a</keycap></term>
 195         <listitem><para>OS X</para></listitem>
 196       </varlistentry>
 197
 198       <varlistentry>
 199         <term><keycap>s</keycap></term>
 200         <listitem><para>EFI shell</para></listitem>
 201       </varlistentry>
 202
 203       <varlistentry>
 204         <term><keycap>1</keycap></term>
 205         <term><keycap>2</keycap></term>
 206         <term><keycap>3</keycap></term>
 207         <term><keycap>4</keycap></term>
 208         <term><keycap>5</keycap></term>
 209         <term><keycap>6</keycap></term>
 210         <term><keycap>7</keycap></term>
 211         <term><keycap>8</keycap></term>
 212         <term><keycap>9</keycap></term>
 213         <listitem><para>Boot entry number 1 … 9</para></listitem>
 214       </varlistentry>
 215     </variablelist>
 216
 217     <para>In the editor, most keys simply insert themselves, but the following keys
 218     may be used to perform additional actions:</para>
 219
 220     <variablelist>
 221       <varlistentry>
 222         <term><keycap>←</keycap> (Left)</term>
 223         <term><keycap>→</keycap> (Right)</term>
 224         <term><keycap>Home</keycap></term>
 225         <term><keycap>End</keycap></term>
 226         <listitem><para>Navigate left/right</para></listitem>
 227       </varlistentry>
 228
 229       <varlistentry>
 230         <term><keycap>Esc</keycap></term>
 231         <listitem><para>Abort the edit and quit the editor</para></listitem>
 232       </varlistentry>
 233
 234       <varlistentry>
 235         <term><keycombo><keycap>Ctrl</keycap><keycap>k</keycap></keycombo></term>
 236         <listitem><para>Clear the command line</para></listitem>
 237       </varlistentry>
 238
 239       <varlistentry>
 240         <term><keycombo><keycap>Ctrl</keycap><keycap>w</keycap></keycombo></term>
 241         <term><keycombo><keycap>Alt</keycap><keycap>Backspace</keycap></keycombo></term>
 242         <listitem><para>Delete word backwards</para></listitem>
 243       </varlistentry>
 244
 245       <varlistentry>
 246         <term><keycombo><keycap>Alt</keycap><keycap>d</keycap></keycombo></term>
 247         <listitem><para>Delete word forwards</para></listitem>
 248       </varlistentry>
 249
 250       <varlistentry>
 251         <term><keycap>↵</keycap> (Enter)</term>
 252         <listitem><para>Boot entry with the edited command line</para></listitem>
 253       </varlistentry>
 254     </variablelist>
 255
 256     <para>Note that unless configured otherwise in the UEFI firmware, systemd-boot will
 257     use the US keyboard layout, so key labels might not match for keys like +/-.
 258     </para>
 259   </refsect1>
 260
 261   <refsect1>
 262     <title>Files</title>
 263
 264     <para>The files <command>systemd-boot</command> processes generally reside on the UEFI ESP which is
 265     usually mounted to <filename>/efi/</filename>, <filename>/boot/</filename> or
 266     <filename>/boot/efi/</filename> during OS runtime. It also processes files on the Extended Boot Loader
 267     partition which is typically mounted to <filename>/boot/</filename>, if it
 268     exists. <command>systemd-boot</command> reads runtime configuration such as the boot timeout and default
 269     entry from <filename>/loader/loader.conf</filename> on the ESP (in combination with data read from EFI
 270     variables). See
 271     <citerefentry><refentrytitle>loader.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Boot
 272     entry description files following the <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot
 273     Loader Specification</ulink> are read from <filename>/loader/entries/</filename> on the ESP and the
 274     Extended Boot Loader partition. Unified kernel boot entries following the <ulink
 275     url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink> are read from
 276     <filename>/EFI/Linux/</filename> on the ESP and the Extended Boot Loader partition. Optionally, a random
 277     seed for early boot entropy pool provisioning is stored in <filename>/loader/random-seed</filename> in
 278     the ESP.</para>
 279   </refsect1>
 280
 281   <refsect1>
 282     <title>EFI Variables</title>
 283
 284     <para>The following EFI variables are defined, set and read by <command>systemd-boot</command>, under the vendor
 285     UUID <literal>4a67b082-0a4c-41cf-b6c7-440b29bb8c4</literal>, for communication between the OS and the boot
 286     loader:</para>
 287
 288     <variablelist class='efi-variables'>
 289       <varlistentry>
 290         <term><varname>LoaderBootCountPath</varname></term>
 291         <listitem><para>If boot counting is enabled, contains the path to the file in whose name the boot counters are
 292         encoded. Set by the boot
 293         loader. <citerefentry><refentrytitle>systemd-bless-boot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 294         uses this information to mark a boot as successful as determined by the successful activation of the
 295         <filename>boot-complete.target</filename> target unit.</para></listitem>
 296       </varlistentry>
 297
 298       <varlistentry>
 299         <term><varname>LoaderConfigTimeout</varname></term>
 300         <term><varname>LoaderConfigTimeoutOneShot</varname></term>
 301         <listitem><para>The menu timeout in seconds. Read by the boot loader. <varname>LoaderConfigTimeout</varname>
 302         is maintained persistently, while <varname>LoaderConfigTimeoutOneShot</varname> is a one-time override which is
 303         read once (in which case it takes precedence over <varname>LoaderConfigTimeout</varname>) and then
 304         removed. <varname>LoaderConfigTimeout</varname> may be manipulated with the
 305         <keycap>t</keycap>/<keycap>T</keycap> keys, see above.)</para></listitem>
 306       </varlistentry>
 307
 308       <varlistentry>
 309         <term><varname>LoaderDevicePartUUID</varname></term>
 310
 311         <listitem><para>Contains the partition UUID of the EFI System Partition the boot loader was run from. Set by
 312         the boot
 313         loader. <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 314         uses this information to automatically find the disk booted from, in order to discover various other partitions
 315         on the same disk automatically.</para></listitem>
 316       </varlistentry>
 317
 318       <varlistentry>
 319         <term><varname>LoaderEntries</varname></term>
 320
 321         <listitem><para>A list of the identifiers of all discovered boot loader entries. Set by the boot
 322         loader.</para></listitem>
 323       </varlistentry>
 324
 325       <varlistentry>
 326         <term><varname>LoaderEntryDefault</varname></term>
 327         <term><varname>LoaderEntryOneShot</varname></term>
 328
 329         <listitem><para>The identifier of the default boot loader entry. Set primarily by the OS and read by the boot
 330         loader. <varname>LoaderEntryOneShot</varname> sets the default entry for the next boot only, while
 331         <varname>LoaderEntryDefault</varname> sets it persistently for all future
 332         boots. <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
 333         <option>set-default</option> and <option>set-oneshot</option> commands make use of these variables. The boot
 334         loader modifies <varname>LoaderEntryDefault</varname> on request, when the <keycap>d</keycap> key is used, see
 335         above.)</para></listitem>
 336       </varlistentry>
 337
 338       <varlistentry>
 339         <term><varname>LoaderEntrySelected</varname></term>
 340
 341         <listitem><para>The identifier of the boot loader entry currently being booted. Set by the boot
 342         loader.</para></listitem>
 343       </varlistentry>
 344
 345       <varlistentry>
 346         <term><varname>LoaderFeatures</varname></term>
 347
 348         <listitem><para>A set of flags indicating the features the boot loader supports. Set by the boot loader. Use
 349         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view this
 350         data.</para></listitem>
 351       </varlistentry>
 352
 353       <varlistentry>
 354         <term><varname>LoaderFirmwareInfo</varname></term>
 355         <term><varname>LoaderFirmwareType</varname></term>
 356
 357         <listitem><para>Brief firmware information. Set by the boot loader. Use
 358         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view this
 359         data.</para></listitem>
 360       </varlistentry>
 361
 362       <varlistentry>
 363         <term><varname>LoaderImageIdentifier</varname></term>
 364
 365         <listitem><para>The path of executable of the boot loader used for the current boot, relative to the EFI System
 366         Partition's root directory. Set by the boot loader. Use
 367         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view this
 368         data.</para></listitem>
 369       </varlistentry>
 370
 371       <varlistentry>
 372         <term><varname>LoaderInfo</varname></term>
 373
 374         <listitem><para>Brief information about the boot loader. Set by the boot loader. Use
 375         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view this
 376         data.</para></listitem>
 377       </varlistentry>
 378
 379       <varlistentry>
 380         <term><varname>LoaderTimeExecUSec</varname></term>
 381         <term><varname>LoaderTimeInitUSec</varname></term>
 382         <term><varname>LoaderTimeMenuUsec</varname></term>
 383
 384         <listitem><para>Information about the time spent in various parts of the boot loader. Set by the boot
 385         loader. Use <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 386         to view this data. </para></listitem>
 387       </varlistentry>
 388
 389       <varlistentry>
 390         <term><varname>LoaderRandomSeed</varname></term>
 391
 392         <listitem><para>A binary random seed <command>systemd-boot</command> may optionally pass to the
 393         OS. This is a volatile EFI variable that is hashed at boot from the combination of a random seed
 394         stored in the ESP (in <filename>/loader/random-seed</filename>) and a "system token" persistently
 395         stored in the EFI variable <varname>LoaderSystemToken</varname> (see below). During early OS boot the
 396         system manager reads this variable and passes it to the OS kernel's random pool, crediting the full
 397         entropy it contains. This is an efficient way to ensure the system starts up with a fully initialized
 398         kernel random pool — as early as the initial RAM disk phase. <command>systemd-boot</command> reads
 399         the random seed from the ESP, combines it with the "system token", and both derives a new random seed
 400         to update in-place the seed stored in the ESP, and the random seed to pass to the OS from it via
 401         SHA256 hashing in counter mode. This ensures that different physical systems that boot the same
 402         "golden" OS image — i.e. containing the same random seed file in the ESP — will still pass a
 403         different random seed to the OS. It is made sure the random seed stored in the ESP is fully
 404         overwritten before the OS is booted, to ensure different random seed data is used between subsequent
 405         boots.</para>
 406
 407         <para>See <ulink url="https://systemd.io/RANDOM_SEEDS">Random Seeds</ulink> for
 408         further information.</para></listitem>
 409       </varlistentry>
 410
 411       <varlistentry>
 412         <term><varname>LoaderSystemToken</varname></term>
 413
 414         <listitem><para>A binary random data field, that is used for generating the random see to pass to the
 415         OS (see above). Note that this random data is generally only generated once, during OS installation,
 416         and is then never updated again.</para></listitem>
 417       </varlistentry>
 418     </variablelist>
 419
 420     <para>Many of these variables are defined by the <ulink
 421     url="https://systemd.io/BOOT_LOADER_INTERFACE">Boot Loader Interface</ulink>.</para>
 422   </refsect1>
 423
 424   <refsect1>
 425     <title>Boot Counting</title>
 426
 427     <para><command>systemd-boot</command> implements a simple boot counting mechanism on top of the <ulink
 428     url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink>, for automatic and unattended
 429     fallback to older kernel versions/boot loader entries when a specific entry continuously fails. Any boot loader
 430     entry file and unified kernel image file that contains a <literal>+</literal> followed by one or two numbers (if
 431     two they need to be separated by a <literal>-</literal>), before the <filename>.conf</filename> or
 432     <filename>.efi</filename> suffix is subject to boot counting: the first of the two numbers ('tries left') is
 433     decreased by one on every boot attempt, the second of the two numbers ('tries done') is increased by one (if 'tries
 434     done' is absent it is considered equivalent to 0). Depending on the current value of these two counters the boot
 435     entry is considered to be in one of three states:</para>
 436
 437     <orderedlist>
 438       <listitem><para>If the 'tries left' counter of an entry is greater than zero the entry is considered to be in
 439       'indeterminate' state. This means the entry has not completed booting successfully yet, but also hasn't been
 440       determined not to work.</para></listitem>
 441
 442       <listitem><para>If the 'tries left' counter of an entry is zero it is considered to be in 'bad' state. This means
 443       no further attempts to boot this item will be made (that is, unless all other boot entries are also in 'bad'
 444       state), as all attempts to boot this entry have not completed successfully.</para></listitem>
 445
 446       <listitem><para>If the 'tries left' and 'tries done' counters of an entry are absent it is considered to be in
 447       'good' state. This means further boot counting for the entry is turned off, as it successfully booted at least
 448       once. The
 449       <citerefentry><refentrytitle>systemd-bless-boot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 450       service moves the currently booted entry from 'indeterminate' into 'good' state when a boot attempt completed
 451       successfully.</para></listitem>
 452     </orderedlist>
 453
 454     <para>Generally, when new entries are added to the boot loader, they first start out in 'indeterminate' state,
 455     i.e. with a 'tries left' counter greater than zero. The boot entry remains in this state until either it managed to
 456     complete a full boot successfully at least once (in which case it will be in 'good' state) — or the 'tries left'
 457     counter reaches zero (in which case it will be in 'bad' state).</para>
 458
 459     <para>Example: let's say a boot loader entry file <filename>foo.conf</filename> is set up for 3 boot tries. The
 460     installer will hence create it under the name <filename>foo+3.conf</filename>. On first boot, the boot loader will
 461     rename it to <filename>foo+2-1.conf</filename>. If that boot does not complete successfully, the boot loader will
 462     rename it to <filename>foo+1-2.conf</filename> on the following boot. If that fails too, it will finally be renamed
 463     <filename>foo+0-3.conf</filename> by the boot loader on next boot, after which it will be considered 'bad'. If the
 464     boot succeeds however the entry file will be renamed to <filename>foo.conf</filename> by the OS, so that it is
 465     considered 'good' from then on.</para>
 466
 467     <para>The boot menu takes the 'tries left' counter into account when sorting the menu entries: entries in 'bad'
 468     state are ordered at the end of the list, and entries in 'good' or 'indeterminate' at the beginning. The user can
 469     freely choose to boot any entry of the menu, including those already marked 'bad'. If the menu entry to boot is
 470     automatically determined, this means that 'good' or 'indeterminate' entries are generally preferred (as the top item of
 471     the menu is the one booted by default), and 'bad' entries will only be considered if there are no 'good' or
 472     'indeterminate' entries left.</para>
 473
 474     <para>The <citerefentry><refentrytitle>kernel-install</refentrytitle><manvolnum>8</manvolnum></citerefentry> kernel
 475     install framework optionally sets the initial 'tries left' counter to the value specified in
 476     <filename>/etc/kernel/tries</filename> when a boot loader entry is first created.</para>
 477   </refsect1>
 478
 479   <refsect1>
 480     <title>See Also</title>
 481     <para>
 482       <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 483       <citerefentry><refentrytitle>loader.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 484       <citerefentry><refentrytitle>systemd-bless-boot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 485       <citerefentry><refentrytitle>systemd-boot-system-token.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 486       <citerefentry><refentrytitle>kernel-install</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 487       <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink>,
 488       <ulink url="https://systemd.io/BOOT_LOADER_INTERFACE">Boot Loader Interface</ulink>
 489     </para>
 490   </refsect1>
 491 </refentry>