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<?xml version='1.0' encoding='utf-8' ?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY % BOOK_ENTITIES SYSTEM "Fedora_Multiboot_Guide.ent">
%BOOK_ENTITIES;
]>
<section id="GRUB-runtime">
<title>Changing GRUB entries at boot</title>
<para>
Changing selection or adding arguments to a GRUB menu entry at boot time can be useful for testing or troubleshooting purposes. You might have a graphics issue to troubleshoot by booting temporarily into a non-graphical <literal>target</literal>, a hardware issue to work around with a <varname>kernel parameter</varname>, or a problem to resolve by selecting an alternate kernel. This section covers the procedure for adding boot arguments, see <xref linkend="boot_arguments" /> for some arguments you might use.
</para>
<!-- this might work better as an independent section, or just a relocated note. -->
<note id="note_rescue-option">
<title>The Rescue option</title>
<para>
The normal boot entries for Fedora use a trimmed down <systemitem class="filesystem">initramfs</systemitem>, or initial boot filesystem. This <literal>host-only</literal> <systemitem class="filesystem">initramfs</systemitem> had information only about the hardware on your computer, allowing the system to boot more quickly by avoid loading unneeded drivers.
</para>
<para>
One of the default menu entries for Fedora is a <literal>rescue</literal> entry. This will load the same Fedora environment as the other entries, but loads a full <systemitem class="filesystem">initramfs</systemitem>.
</para>
<para>
The rescue option is useful if you have problems after adding new hardware. You can use the rescue option to regenerate the <systemitem class="filesystem">initramfs</systemitem> for all boot entries using this command, executed with root privileges:
<screen>
<command>dracut --regenerate-all --force</command>
</screen>
</para>
</note>
<procedure id="GRUB-add_boot_parameter">
<step>
<para>
Turn on or reboot your computer. When the GRUB menu ( <xref linkend="grub-menu" /> ) appears, press the <keycap>Esc</keycap> key to stop the countdown.
</para>
<figure id="grub-menu">
<title>GRUB menu during countdown</title>
<mediaobject>
<imageobject>
<!-- 800x450 px, 16:9 -->
<imagedata fileref="images/grub-menu-countdown.png" format="PNG" scalefit="0" />
</imageobject>
<textobject>
<para>
The GRUB menu is a text based interface with a list of bootable systems. The entries for Fedora include the kernels available to boot and the rescue option. The menu counts down from a defined value, 5 seconds by default, before booting the default entry.
</para>
</textobject>
</mediaobject>
</figure>
</step>
<step>
<para>
Use the arrow keys to highlight the desired boot entry.
</para>
<substeps>
<step>
<para>
If you want to boot an alternate menu entry without editing, press <keycap>Enter</keycap> to continue.
</para>
</step>
<step>
<para>
If you want to edit the entry before booting, press <keycap>e</keycap> to edit.
</para>
</step>
</substeps>
</step>
<step>
<substeps>
<step>
<para>
The initial screen displayed for editing shows information GRUB needs to find and boot the operating system, as pictured in <xref linkend="grub-menu-edit_initial" />. These lines should not be changed.
</para>
<figure id="grub-menu-edit_initial">
<title>The GRUB edit screen, Part 1</title>
<mediaobject>
<imageobject>
<!-- 800x450 px, 16:9 -->
<imagedata fileref="images/grub-menu-edit_initial.png" format="PNG" scalefit="0" />
</imageobject>
<textobject>
<para>
The initial edit screen shows several lines of parameters and modules that GRUB uses to boot the operating system.
</para>
</textobject>
</mediaobject>
</figure>
</step>
<step>
<para>
Using the arrow keys, move down to the line that contains the boot arguments. On UEFI systems, this line will begin with <parameter>linuxefi</parameter>, or on BIOS systems the line will begin with <parameter>linux</parameter>. The next argument on the line will typically be the kernel, a string beginning with <literal>/vmlinuz-</literal>. This is shown in <xref linkend="grub-menu-edit_scrolled" />.
</para>
<para>
Press the <keycap>End</keycap> key to move to the end of the line.
</para>
<figure id="grub-menu-edit_scrolled">
<title>The GRUB edit screen, Part 1</title>
<mediaobject>
<imageobject>
<!-- 800x450 px, 16:9 -->
<imagedata fileref="images/grub-menu-edit_scrolled.png" format="PNG" scalefit="0" />
</imageobject>
<textobject>
<para>
Scrolling down reveals the line with boot arguments.
</para>
</textobject>
</mediaobject>
</figure>
<note id="verbose_boot-rhgb_quiet">
<title>Getting more information during boot</title>
<para>
The default boot parameters for Fedora include <parameter>rghb</parameter> and <parameter>quiet</parameter>. These enable the boot splash screen instead of showing details about services, mountpoints, and other units as the sytem boots. If you are troubleshooting a boot issue or want to see more information when Fedora loads, removing these parameters will disable the splash screen.
</para>
</note>
</step>
</substeps>
</step>
<step>
<para>
Type in your desired parameters and press <keycombo><keycap>Ctrl</keycap><keycap>x</keycap></keycombo> to boot. See <xref linkend="boot_arguments" /> for some parameters you might find useful.
</para>
</step>
</procedure>
</section>
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