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 persistant 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         <listitem><para>Boot selected entry</para></listitem>
 127       </varlistentry>
 128
 129       <varlistentry>
 130         <term><keycap>d</keycap></term>
 131         <listitem><para>Make selected entry the default</para></listitem>
 132       </varlistentry>
 133
 134       <varlistentry>
 135         <term><keycap>e</keycap></term>
 136         <listitem><para>Edit the kernel command line for selected entry</para></listitem>
 137       </varlistentry>
 138
 139       <varlistentry>
 140         <term><keycap>+</keycap></term>
 141         <term><keycap>t</keycap></term>
 142         <listitem><para>Increase the timeout before default entry is booted</para></listitem>
 143       </varlistentry>
 144
 145       <varlistentry>
 146         <term><keycap>-</keycap></term>
 147         <term><keycap>T</keycap></term>
 148         <listitem><para>Decrease the timeout</para></listitem>
 149       </varlistentry>
 150
 151       <varlistentry>
 152         <term><keycap>v</keycap></term>
 153         <listitem><para>Show systemd-boot, UEFI, and firmware versions</para></listitem>
 154       </varlistentry>
 155
 156       <varlistentry>
 157         <term><keycap>P</keycap></term>
 158         <listitem><para>Print status</para></listitem>
 159       </varlistentry>
 160
 161       <varlistentry>
 162         <term><keycap>Q</keycap></term>
 163         <listitem><para>Quit</para></listitem>
 164       </varlistentry>
 165
 166       <varlistentry>
 167         <term><keycap>h</keycap></term>
 168         <term><keycap>?</keycap></term>
 169         <listitem><para>Show a help screen</para></listitem>
 170       </varlistentry>
 171
 172       <varlistentry>
 173         <term><keycombo><keycap>Ctrl</keycap><keycap>l</keycap></keycombo></term>
 174         <listitem><para>Reprint the screen</para></listitem>
 175       </varlistentry>
 176     </variablelist>
 177
 178     <para>The following keys may be used during bootup or in the boot menu to
 179     directly boot a specific entry:</para>
 180
 181     <variablelist>
 182       <varlistentry>
 183         <term><keycap>l</keycap></term>
 184         <listitem><para>Linux</para></listitem>
 185       </varlistentry>
 186
 187       <varlistentry>
 188         <term><keycap>w</keycap></term>
 189         <listitem><para>Windows</para></listitem>
 190       </varlistentry>
 191
 192       <varlistentry>
 193         <term><keycap>a</keycap></term>
 194         <listitem><para>OS X</para></listitem>
 195       </varlistentry>
 196
 197       <varlistentry>
 198         <term><keycap>s</keycap></term>
 199         <listitem><para>EFI shell</para></listitem>
 200       </varlistentry>
 201
 202       <varlistentry>
 203         <term><keycap>1</keycap></term>
 204         <term><keycap>2</keycap></term>
 205         <term><keycap>3</keycap></term>
 206         <term><keycap>4</keycap></term>
 207         <term><keycap>5</keycap></term>
 208         <term><keycap>6</keycap></term>
 209         <term><keycap>7</keycap></term>
 210         <term><keycap>8</keycap></term>
 211         <term><keycap>9</keycap></term>
 212         <listitem><para>Boot entry number 1 … 9</para></listitem>
 213       </varlistentry>
 214     </variablelist>
 215
 216     <para>In the editor, most keys simply insert themselves, but the following keys
 217     may be used to perform additional actions:</para>
 218
 219     <variablelist>
 220       <varlistentry>
 221         <term><keycap>←</keycap> (Left)</term>
 222         <term><keycap>→</keycap> (Right)</term>
 223         <term><keycap>Home</keycap></term>
 224         <term><keycap>End</keycap></term>
 225         <listitem><para>Navigate left/right</para></listitem>
 226       </varlistentry>
 227
 228       <varlistentry>
 229         <term><keycap>Esc</keycap></term>
 230         <listitem><para>Abort the edit and quit the editor</para></listitem>
 231       </varlistentry>
 232
 233       <varlistentry>
 234         <term><keycombo><keycap>Ctrl</keycap><keycap>k</keycap></keycombo></term>
 235         <listitem><para>Clear the command line</para></listitem>
 236       </varlistentry>
 237
 238       <varlistentry>
 239         <term><keycombo><keycap>Ctrl</keycap><keycap>w</keycap></keycombo></term>
 240         <term><keycombo><keycap>Alt</keycap><keycap>Backspace</keycap></keycombo></term>
 241         <listitem><para>Delete word backwards</para></listitem>
 242       </varlistentry>
 243
 244       <varlistentry>
 245         <term><keycombo><keycap>Alt</keycap><keycap>d</keycap></keycombo></term>
 246         <listitem><para>Delete word forwards</para></listitem>
 247       </varlistentry>
 248
 249       <varlistentry>
 250         <term><keycap>↵</keycap> (Enter)</term>
 251         <listitem><para>Boot entry with the edited command line</para></listitem>
 252       </varlistentry>
 253     </variablelist>
 254
 255     <para>Note that unless configured otherwise in the UEFI firmware, systemd-boot will
 256     use the US keyboard layout, so key labels might not match for keys like +/-.
 257     </para>
 258   </refsect1>
 259
 260   <refsect1>
 261     <title>Files</title>
 262
 263     <para>The files <command>systemd-boot</command> processes generally reside on the UEFI ESP which is
 264     usually mounted to <filename>/efi/</filename>, <filename>/boot/</filename> or
 265     <filename>/boot/efi/</filename> during OS runtime. It also processes files on the Extended Boot Loader
 266     partition which is typically mounted to <filename>/boot/</filename>, if it
 267     exists. <command>systemd-boot</command> reads runtime configuration such as the boot timeout and default
 268     entry from <filename>/loader/loader.conf</filename> on the ESP (in combination with data read from EFI
 269     variables). See
 270     <citerefentry><refentrytitle>loader.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Boot
 271     entry description files following the <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot
 272     Loader Specification</ulink> are read from <filename>/loader/entries/</filename> on the ESP and the
 273     Extended Boot Loader partition. Unified kernel boot entries following the <ulink
 274     url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink> are read from
 275     <filename>/EFI/Linux/</filename> on the ESP and the Extended Boot Loader partition. Optionally, a random
 276     seed for early boot entropy pool provisioning is stored in <filename>/loader/random-seed</filename> in
 277     the ESP.</para>
 278   </refsect1>
 279
 280   <refsect1>
 281     <title>EFI Variables</title>
 282
 283     <para>The following EFI variables are defined, set and read by <command>systemd-boot</command>, under the vendor
 284     UUID <literal>4a67b082-0a4c-41cf-b6c7-440b29bb8c4</literal>, for communication between the OS and the boot
 285     loader:</para>
 286
 287     <variablelist class='efi-variables'>
 288       <varlistentry>
 289         <term><varname>LoaderBootCountPath</varname></term>
 290         <listitem><para>If boot counting is enabled, contains the path to the file in whose name the boot counters are
 291         encoded. Set by the boot
 292         loader. <citerefentry><refentrytitle>systemd-bless-boot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 293         uses this information to mark a boot as successful as determined by the successful activation of the
 294         <filename>boot-complete.target</filename> target unit.</para></listitem>
 295       </varlistentry>
 296
 297       <varlistentry>
 298         <term><varname>LoaderConfigTimeout</varname></term>
 299         <term><varname>LoaderConfigTimeoutOneShot</varname></term>
 300         <listitem><para>The menu timeout in seconds. Read by the boot loader. <varname>LoaderConfigTimeout</varname>
 301         is maintained persistently, while <varname>LoaderConfigTimeoutOneShot</varname> is a one-time override which is
 302         read once (in which case it takes precedence over <varname>LoaderConfigTimeout</varname>) and then
 303         removed. <varname>LoaderConfigTimeout</varname> may be manipulated with the
 304         <keycap>t</keycap>/<keycap>T</keycap> keys, see above.)</para></listitem>
 305       </varlistentry>
 306
 307       <varlistentry>
 308         <term><varname>LoaderDevicePartUUID</varname></term>
 309
 310         <listitem><para>Contains the partition UUID of the EFI System Partition the boot loader was run from. Set by
 311         the boot
 312         loader. <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 313         uses this information to automatically find the disk booted from, in order to discover various other partitions
 314         on the same disk automatically.</para></listitem>
 315       </varlistentry>
 316
 317       <varlistentry>
 318         <term><varname>LoaderEntries</varname></term>
 319
 320         <listitem><para>A list of the identifiers of all discovered boot loader entries. Set by the boot
 321         loader.</para></listitem>
 322       </varlistentry>
 323
 324       <varlistentry>
 325         <term><varname>LoaderEntryDefault</varname></term>
 326         <term><varname>LoaderEntryOneShot</varname></term>
 327
 328         <listitem><para>The identifier of the default boot loader entry. Set primarily by the OS and read by the boot
 329         loader. <varname>LoaderEntryOneShot</varname> sets the default entry for the next boot only, while
 330         <varname>LoaderEntryDefault</varname> sets it persistently for all future
 331         boots. <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
 332         <option>set-default</option> and <option>set-oneshot</option> commands make use of these variables. The boot
 333         loader modifies <varname>LoaderEntryDefault</varname> on request, when the <keycap>d</keycap> key is used, see
 334         above.)</para></listitem>
 335       </varlistentry>
 336
 337       <varlistentry>
 338         <term><varname>LoaderEntrySelected</varname></term>
 339
 340         <listitem><para>The identifier of the boot loader entry currently being booted. Set by the boot
 341         loader.</para></listitem>
 342       </varlistentry>
 343
 344       <varlistentry>
 345         <term><varname>LoaderFeatures</varname></term>
 346
 347         <listitem><para>A set of flags indicating the features the boot loader supports. Set by the boot loader. Use
 348         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view this
 349         data.</para></listitem>
 350       </varlistentry>
 351
 352       <varlistentry>
 353         <term><varname>LoaderFirmwareInfo</varname></term>
 354         <term><varname>LoaderFirmwareType</varname></term>
 355
 356         <listitem><para>Brief firmware information. Set by the boot loader. Use
 357         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view this
 358         data.</para></listitem>
 359       </varlistentry>
 360
 361       <varlistentry>
 362         <term><varname>LoaderImageIdentifier</varname></term>
 363
 364         <listitem><para>The path of executable of the boot loader used for the current boot, relative to the EFI System
 365         Partition's root directory. Set by the boot loader. Use
 366         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view this
 367         data.</para></listitem>
 368       </varlistentry>
 369
 370       <varlistentry>
 371         <term><varname>LoaderInfo</varname></term>
 372
 373         <listitem><para>Brief information about the boot loader. Set by the boot loader. Use
 374         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view this
 375         data.</para></listitem>
 376       </varlistentry>
 377
 378       <varlistentry>
 379         <term><varname>LoaderTimeExecUSec</varname></term>
 380         <term><varname>LoaderTimeInitUSec</varname></term>
 381         <term><varname>LoaderTimeMenuUsec</varname></term>
 382
 383         <listitem><para>Information about the time spent in various parts of the boot loader. Set by the boot
 384         loader. Use <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 385         to view this data. </para></listitem>
 386       </varlistentry>
 387
 388       <varlistentry>
 389         <term><varname>LoaderRandomSeed</varname></term>
 390
 391         <listitem><para>A binary random seed <command>systemd-boot</command> may optionally pass to the
 392         OS. This is a volatile EFI variable that is hashed at boot from the combination of a random seed
 393         stored in the ESP (in <filename>/loader/random-seed</filename>) and a "system token" persistently
 394         stored in the EFI variable <varname>LoaderSystemToken</varname> (see below). During early OS boot the
 395         system manager reads this variable and passes it to the OS kernel's random pool, crediting the full
 396         entropy it contains. This is an efficient way to ensure the system starts up with a fully initialized
 397         kernel random pool — as early as the initial RAM disk phase. <command>systemd-boot</command> reads
 398         the random seed from the ESP, combines it with the "system token", and both derives a new random seed
 399         to update in-place the seed stored in the ESP, and the random seed to pass to the OS from it via
 400         SHA256 hashing in counter mode. This ensures that different physical systems that boot the same
 401         "golden" OS image — i.e. containing the same random seed file in the ESP — will still pass a
 402         different random seed to the OS. It is made sure the random seed stored in the ESP is fully
 403         overwritten before the OS is booted, to ensure different random seed data is used between subsequent
 404         boots.</para>
 405
 406         <para>See <ulink url="https://systemd.io/RANDOM_SEEDS">Random Seeds</ulink> for
 407         further information.</para></listitem>
 408       </varlistentry>
 409
 410       <varlistentry>
 411         <term><varname>LoaderSystemToken</varname></term>
 412
 413         <listitem><para>A binary random data field, that is used for generating the random see to pass to the
 414         OS (see above). Note that this random data is generally only generated once, during OS installation,
 415         and is then never updated again.</para></listitem>
 416       </varlistentry>
 417     </variablelist>
 418
 419     <para>Many of these variables are defined by the <ulink
 420     url="https://systemd.io/BOOT_LOADER_INTERFACE">Boot Loader Interface</ulink>.</para>
 421   </refsect1>
 422
 423   <refsect1>
 424     <title>Boot Counting</title>
 425
 426     <para><command>systemd-boot</command> implements a simple boot counting mechanism on top of the <ulink
 427     url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink>, for automatic and unattended
 428     fallback to older kernel versions/boot loader entries when a specific entry continuously fails. Any boot loader
 429     entry file and unified kernel image file that contains a <literal>+</literal> followed by one or two numbers (if
 430     two they need to be separated by a <literal>-</literal>), before the <filename>.conf</filename> or
 431     <filename>.efi</filename> suffix is subject to boot counting: the first of the two numbers ('tries left') is
 432     decreased by one on every boot attempt, the second of the two numbers ('tries done') is increased by one (if 'tries
 433     done' is absent it is considered equivalent to 0). Depending on the current value of these two counters the boot
 434     entry is considered to be in one of three states:</para>
 435
 436     <orderedlist>
 437       <listitem><para>If the 'tries left' counter of an entry is greater than zero the entry is considered to be in
 438       'indeterminate' state. This means the entry has not completed booting successfully yet, but also hasn't been
 439       determined not to work.</para></listitem>
 440
 441       <listitem><para>If the 'tries left' counter of an entry is zero it is considered to be in 'bad' state. This means
 442       no further attempts to boot this item will be made (that is, unless all other boot entries are also in 'bad'
 443       state), as all attempts to boot this entry have not completed successfully.</para></listitem>
 444
 445       <listitem><para>If the 'tries left' and 'tries done' counters of an entry are absent it is considered to be in
 446       'good' state. This means further boot counting for the entry is turned off, as it successfully booted at least
 447       once. The
 448       <citerefentry><refentrytitle>systemd-bless-boot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 449       service moves the currently booted entry from 'indeterminate' into 'good' state when a boot attempt completed
 450       successfully.</para></listitem>
 451     </orderedlist>
 452
 453     <para>Generally, when new entries are added to the boot loader, they first start out in 'indeterminate' state,
 454     i.e. with a 'tries left' counter greater than zero. The boot entry remains in this state until either it managed to
 455     complete a full boot successfully at least once (in which case it will be in 'good' state) — or the 'tries left'
 456     counter reaches zero (in which case it will be in 'bad' state).</para>
 457
 458     <para>Example: let's say a boot loader entry file <filename>foo.conf</filename> is set up for 3 boot tries. The
 459     installer will hence create it under the name <filename>foo+3.conf</filename>. On first boot, the boot loader will
 460     rename it to <filename>foo+2-1.conf</filename>. If that boot does not complete successfully, the boot loader will
 461     rename it to <filename>foo+1-2.conf</filename> on the following boot. If that fails too, it will finally be renamed
 462     <filename>foo+0-3.conf</filename> by the boot loader on next boot, after which it will be considered 'bad'. If the
 463     boot succeeds however the entry file will be renamed to <filename>foo.conf</filename> by the OS, so that it is
 464     considered 'good' from then on.</para>
 465
 466     <para>The boot menu takes the 'tries left' counter into account when sorting the menu entries: entries in 'bad'
 467     state are ordered at the end of the list, and entries in 'good' or 'indeterminate' at the beginning. The user can
 468     freely choose to boot any entry of the menu, including those already marked 'bad'. If the menu entry to boot is
 469     automatically determined, this means that 'good' or 'indeterminate' entries are generally preferred (as the top item of
 470     the menu is the one booted by default), and 'bad' entries will only be considered if there are no 'good' or
 471     'indeterminate' entries left.</para>
 472
 473     <para>The <citerefentry><refentrytitle>kernel-install</refentrytitle><manvolnum>8</manvolnum></citerefentry> kernel
 474     install framework optionally sets the initial 'tries left' counter to the value specified in
 475     <filename>/etc/kernel/tries</filename> when a boot loader entry is first created.</para>
 476   </refsect1>
 477
 478   <refsect1>
 479     <title>See Also</title>
 480     <para>
 481       <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 482       <citerefentry><refentrytitle>loader.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 483       <citerefentry><refentrytitle>systemd-bless-boot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 484       <citerefentry><refentrytitle>systemd-boot-system-token.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 485       <citerefentry><refentrytitle>kernel-install</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 486       <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink>,
 487       <ulink url="https://systemd.io/BOOT_LOADER_INTERFACE">Boot Loader Interface</ulink>
 488     </para>
 489   </refsect1>
 490 </refentry>