Chapter 3. Customizing the boot menu

append - contains additional kernel options. The initrd= and inst.stage2 options are mandatory; you can add others.

For information about the options that are applicable to Anaconda refer to Red Hat Enterprise Linux 9 Performing a standard RHEL 9 installation Guide.

One of the notable options is inst.ks=, which allows you to specify a location of a Kickstart file. You can place a Kickstart file on the boot ISO image and use the inst.ks= option to specify its location; for example, you can place a kickstart.ks file into the image’s root directory and use inst.ks=hd:LABEL=RHEL-9-BaseOS-x86_64:/kickstart.ks.

You can also use dracut options which are listed on the dracut.cmdline(7) man page.

timeout - determines the time for which the boot menu is displayed before the default menu entry is automatically used. The default value is 600, which means the menu is displayed for 60 seconds. Setting this value to 0 disables the timeout option.

menu begin and menu end - determines a start and end of a submenu block, allowing you to add additional options such as troubleshooting and grouping them in a submenu. A simple submenu with two options (one to continue and one to go back to the main menu) looks similar to the following:

menu begin ^Troubleshooting
  menu title Troubleshooting

label rescue
  menu label ^Rescue a Red Hat Enterprise Linux system
  kernel vmlinuz
  append initrd=initrd.img inst.stage2=hd:LABEL=RHEL-9-BaseOS-x86_64 rescue quiet

menu separator

label returntomain
  menu label Return to ^main menu
  menu exit

menu end

The submenu entry definitions are similar to normal menu entries, but grouped between menu begin and menu end statements. The menu exit line in the second option exits the submenu and returns to the main menu.

menu color - determines the color of a menu element. The full format is:

menu color element ansi foreground background shadow

Most important parts of this command are:

foreground and background - determine the actual colors.

The colors are described using an #AARRGGBB notation in hexadecimal format determines opacity:

menuentry - Defines the title of the entry. It is specified in single or double quotes (' or "). You can use the --class option to group menu entries into different classes, which can then be styled differently using GRUB2 themes.

linuxefi - Defines the kernel that boots (/images/pxeboot/vmlinuz in the above example) and the other additional options, if any.

You can customize these options to change the behavior of the boot entry. For details about the options that are applicable to Anaconda, see Performing an advanced RHEL 9 installation.

One of the notable options is inst.ks=, which allows you to specify a location of a Kickstart file. You can place a Kickstart file on the boot ISO image and use the inst.ks= option to specify its location; for example, you can place a kickstart.ks file into the image’s root directory and use inst.ks=hd:LABEL=RHEL-9-BaseOS-x86_64:/kickstart.ks.

You can also use dracut options which are listed on the dracut.cmdline(7) man page.

set timeout - determines how long is the boot menu displayed before the default menu entry is automatically used. The default value is 60, which means the menu is displayed for 60 seconds. Setting this value to -1 disables the timeout completely.

submenu - A submenu block allows you to create a sub-menu and group some entries under it, instead of displaying them in the main menu. The Troubleshooting submenu in the default configuration contains entries for rescuing an existing system.

The title of the entry is in single or double quotes (' or ").

The submenu block contains one or more menuentry definitions as described above, and the entire block is enclosed in curly braces ({}). For example:

submenu 'Submenu title' {
  menuentry 'Submenu option 1' {
    linuxefi /images/vmlinuz inst.stage2=hd:LABEL=RHEL-9-BaseOS-x86_64 xdriver=vesa nomodeset quiet
    initrdefi /images/pxeboot/initrd.img
  }
  menuentry 'Submenu option 2' {
    linuxefi /images/vmlinuz inst.stage2=hd:LABEL=RHEL-9-BaseOS-x86_64 rescue quiet
    initrdefi /images/initrd.img
  }
}