# Multiboot USB drive

Related articles

- GRUB
- Syslinux
- Archiso

This article or section is a candidate for moving to Multiboot disk images.

Notes: See discussion (Discuss in Talk:Multiboot USB drive#Scope and title)

A multiboot USB flash drive allows booting multiple ISO files from a single device. The ISO files can be copied to the device and booted directly without unpacking them first. There are multiple methods available, but they may not work for all ISO images.

## Using GRUB and loopback devices

This article or section needs language, wiki syntax or style improvements.

Reason: multiple style issues (Discuss in Talk:Multiboot USB drive#)

advantages:

- only a single partition required
- all ISO files are found in one directory
- adding and removing ISO files is simple

disadvantages:

- not all ISO images are compatible
- the original boot menu for the ISO file is not shown
- it can be difficult to find a working boot entry

### Preparation

This article or section needs expansion.

Reason: How much extra space is needed for the bootloader? (Discuss in Talk:Multiboot USB drive#)

Create at least one partition and a filesystem supported by GRUB on the USB drive. See Partitioning and File systems#Create a file system. Choose the size based on the total size of the ISO files that you want to store on the drive, and plan for extra space for the bootloader.

### Installing GRUB

#### Simple installation

Mount the filesystem located on the USB drive:

    # mount /dev/sdXY /mnt

Create the directory /boot:

    # mkdir /mnt/boot

Install grub on the USB drive:

    # grub-install --target=i386-pc --recheck --boot-directory=/mnt/boot /dev/sdX

In case you want to boot ISOs in UEFI mode, you have to install grub for the UEFI target:

    # grub-install --target x86_64-efi --efi-directory /mnt --boot-directory=/mnt/boot --removable

For UEFI, the partition has to be the first one in an MBR partition table and formatted with FAT32.

#### Hybrid UEFI GPT + BIOS GPT/MBR boot

This configuration is useful for creating an universal USB key, bootable everywhere. First of all you must create a GPT partition table on your device. You need at least 3 partitions:

1. A BIOS boot partition (type EF02)
2. An EFI System partition (type EF00 with a FAT32 filesystem)
3. Your data partition (use a filesystem supported by GRUB)

The BIOS boot partition must be sized 1 MB, while the EFI System partition can be at least as small as 50 MB. The data partition can take up the rest of the space of your drive.

Next you must create a hybrid MBR partition table, as setting the boot flag on the protective MBR partition might not be enough.

Hybrid MBR partition table creation example using gdisk:

    $ gdisk /dev/sdX

    Command (? for help): r
    Recovery/transformation command (? for help): h
    Type from one to three GPT partition numbers, separated by spaces, to be added to the hybrid MBR, in sequence: 1 2 3
    Place EFI GPT (0xEE) partition first in MBR (good for GRUB)? (Y/N): N

    Creating entry for GPT partition #1 (MBR partition #2)
    Enter an MBR hex code (default EF):
    Set the bootable flag? (Y/N): N

    Creating entry for GPT partition #2 (MBR partition #3)
    Enter an MBR hex code (default EF):
    Set the bootable flag? (Y/N): N

    Creating entry for GPT partition #3 (MBR partition #4)
    Enter an MBR hex code (default 83):
    Set the bootable flag? (Y/N): Y

    Recovery/transformation command (? for help): x
    Expert command (? for help): h
    Expert command (? for help): w

    Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
    PARTITIONS!!

    Do you want to proceed? (Y/N): Y

You can now install GRUB to support both EFI + GPT and BIOS + GPT/MBR. The GRUB configuration (--boot-directory) can be kept in the same place.

First, you need to mount the EFI System partition and the data partition of your USB drive. Then, you can install GRUB for EFI with:

    $ grub-install --target=x86_64-efi --efi-directory=/EFI_MOUNTPOINT --boot-directory=/DATA_MOUNTPOINT/boot --removable --recheck

And for BIOS with:

    $ grub-install --target=i386-pc --boot-directory=/DATA_MOUNTPOINT/boot --recheck /dev/sdX

As an additional fallback, you can also install GRUB on your MBR-bootable data partition:

    $ grub-install --target=i386-pc --boot-directory=/DATA_MOUNTPOINT/boot --recheck /dev/sdX3

### Configuring GRUB

#### Using a template

There are some git projects which provide some pre-existing GRUB configuration files, and a nice generic grub.cfg which can be used to load the other boot entries on demand, showing them only if the specified ISO files - or folders containing them - are present on the drive.

Multiboot USB: https://github.com/aguslr/multibootusb

GLIM (GRUB2 Live ISO Multiboot): https://github.com/thias/glim

#### Manual configuration

For the purpose of multiboot USB drive it is easier to edit `grub.cfg` by hand instead of generating it. Alternatively, make the following changes in `/etc/grub.d/40_custom` or `/mnt/boot/grub/custom.cfg` and generate `/mnt/boot/grub/grub.cfg` using grub-mkconfig.

As it is recommend to use a persistent name instead of `/dev/sdxY` to identify the partition on the USB drive where the image files are located, define a variable for convenience to hold the value. If the ISO images are on the same partition as grub, use the following to read the UUID at boot time:

    /mnt/boot/grub/grub.cfg

    # path to the partition holding ISO images (using UUID)
    probe -u $root --set=rootuuid
    set imgdevpath="/dev/disk/by-uuid/$rootuuid"

Or specify the UUID explicitly:

    /mnt/boot/grub/grub.cfg

    # path to the partition holding ISO images (using UUID)
    set imgdevpath="/dev/disk/by-uuid/UUID_value"

Alternatively, use the device label instead of UUID:

    /mnt/boot/grub/grub.cfg

    # path to the partition holding ISO images (using labels)
    set imgdevpath="/dev/disk/by-label/label_value"

The necessary UUID or label can be found using `lsblk -f`. Do not use the same label as the Arch ISO for the USB device, otherwise the boot process will fail.

To complete the configuration, a boot entry for each ISO image has to be added below this header, see the next section for examples.

### Boot entries

This section is being considered for removal.

Reason: Besides the actual Arch entry, this is unrelated content to Arch (Discuss in Talk:Multiboot_USB_drive#Scope_and_title)

This article or section needs language, wiki syntax or style improvements.

Reason: The only boxes used should be code blocks, otherwise the section will be unreadable. Anything else should be plain text. (Discuss in Talk:Multiboot USB drive#)

It is assumed that the ISO images are stored in the `boot/iso/` directory on the same filesystem where GRUB is installed. Otherwise it would be necessary to prefix the path to ISO file with device identification when using the `loopback` command, for example `loopback loop (hd1,2)$isofile`. As this identification of devices is not persistent, it is not used in the examples in this section.

One can use persistent block device naming like this:

    # define globally (i.e outside any menuentry)
    insmod search_fs_uuid
    search --no-floppy --set=isopart --fs-uuid d6de9100-1981-11e5-9fb9-74867a652f05         # your iso fs uuid here
    # later use inside each menuentry instead
    loopback loop ($isopart)$isofile

Tip: For a list of kernel parameters, see https://www.kernel.org/doc/Documentation/kernel-parameters.txt (still incomplete)

#### Alpine Linux

Tip: If you want to boot into a 32-bit system, replace `x86_64` with `x86`.

- Initramfs framework: ???
- Live framework: ???
- Init system: OpenRC (cmdline: RFD)

    menuentry '[loopback]alpine x86_64' {
            set isofile='/boot/iso/alpine-3.3.3-x86_64.iso'
            loopback loop $isofile
            set root=loop
            linux /boot/vmlinuz-grsec modloop=/boot/modloop-grsec modules=loop,squashfs,sd-mod,usb-storage quiet
            initrd /boot/initramfs-grsec
    }

#### Alt Linux

- Initramfs framework: ???
- Live framework: ???
- Init system: ???

    menuentry "[loopback]altlinux-7.0.5-simply-x86_64-install-dvd5.iso" {
            set gfxpayload=keep
    	insmod gzio
    	insmod part_msdos
    	insmod ext2
    	insmod xfs
            set bootpart=uuid:df46d821-e7f9-4e35-bbd2-728bdce8d89a
            set isodir=/boot/iso
            set isofile=altlinux-7.0.5-simply-x86_64-install-dvd5.iso
            loopback loop (${root})${isodir}/${isofile}
            linux (loop)/syslinux/alt0/vmlinuz automatic=method:disk,${bootpart},directory:${isodir}/${isofile} ramdisk_size=183210 changedisk lang=ru_RU splash noeject xdriver=auto quiet=1 showopts
            initrd (loop)/syslinux/alt0/full.cz
    }

#### Arch Linux

Tip: If you want to boot into a 32-bit system, replace `x86_64` with `i686`.

##### monthly release

- Initramfs framework: mkinitcpio (cmdline: [1])
- Live framework: archiso (cmdline: [2])
- Init system: systemd (cmdline: [3])

    menuentry '[loopback]archlinux-2014.12.01-dual.iso' {
    	set isofile='/boot/iso/archlinux-2014.12.01-dual.iso'
    	loopback loop $isofile
    	linux (loop)/arch/boot/x86_64/vmlinuz archisodevice=/dev/loop0 img_dev=$imgdevpath img_loop=$isofile earlymodules=loop
    	initrd (loop)/arch/boot/x86_64/archiso.img
    }

Note: As of archiso v23 (monthly release 2015.10.01), the parameter `archisodevice=/dev/loop0` is no longer necessary when boot using GRUB and loopback devices.

##### archboot

- Initramfs framework: mkinitcpio (cmdline: [4])
- Live framework: archboot (cmdline: none? RFD)
- Init system: systemd (cmdline: [5])

    menuentry '[loopback]archlinux-2014.11-1-archboot' {
    	set isofile='/boot/iso/archlinux-2014.11-1-archboot.iso'
    	loopback loop $isofile
    	linux (loop)/boot/vmlinuz_x86_64 iso_loop_dev=$imgdevpath iso_loop_path=$isofile
    	initrd (loop)/boot/initramfs_x86_64.img
    }

#### CentOS

##### Stock installation medium

- Initramfs framework: Dracut (cmdline: [6])
- Installation program: Anaconda (cmdline: [7])
- Init system: systemd (cmdline: [8])

    menuentry "[loopback]CentOS-7.0-1406-x86_64-DVD" {
    	set isofile='/boot/iso/CentOS-7.0-1406-x86_64-DVD.iso'
    	loopback loop $isofile
    	linux (loop)/isolinux/vmlinuz noeject inst.stage2=hd:/dev/sdb2:/$isofile
    	initrd (loop)/isolinux/initrd.img
    }

Tip: The boot parameter of second stage install image location `/dev/sdb2` which is used by Anaconda, is similar to fstab's first field (fs_spec), could be replaced with one of:

- `/dev/sdxY`
- `LABEL=MYUSBSTICK`
- `UUID=00000000-0000-0000-0000-0000deadbeef`

For example, `linux (loop)/isolinux/vmlinuz noeject inst.stage2=hd:LABEL=MYUSBSTICK:/$isofile`.

When using some special disk label (e.g. GPT), it's also possible to use `PARTUUID=` and/or `PARTLABEL=`.

##### Desktop live medium

- Initramfs framework: Dracut (cmdline: [9])
- Live framework: fedora livecd-tools (cmdline: none)
- Init system: systemd (cmdline: [10])

    menuentry '[loopback]CentOS-7.0-1406-x86_64-GnomeLive' {
    	set isofile='/boot/iso/CentOS-7.0-1406-x86_64-GnomeLive.iso'
    	loopback loop $isofile
    	linux (loop)/isolinux/vmlinuz0 root=live:CDLABEL=CentOS-7-live-GNOME-x86_64 iso-scan/filename=$isofile rd.live.image
    	initrd (loop)/isolinux/initrd0.img
    }

#### Clonezilla Live

Tip: Since 2014.01.05[11], the Arch Linux monthly release contains clonezilla.

- Initramfs framework: initramfs-tools (cmdline: RFD)
- Live framework: Debian Live (cmdline: [12])
- Init system: sysvinit (cmdline: RFD)

    menuentry "[loopback]clonezilla-live-2.2.3-25-amd64" {
    	set isofile="/boot/iso/clonezilla-live-2.2.3-25-amd64.iso"
    	loopback loop $isofile
    	linux (loop)/live/vmlinuz findiso=$isofile boot=live union=overlay username=user config
    	initrd (loop)/live/initrd.img
    }

#### Debian

##### Stock install medium

- Initramfs framework: initramfs-tools (cmdline: RFD)
- Installation program: debian-installer (cmdline: exists but missing online documentation)
- Init system: sysvinit (cmdline: RFD)

Tip: To install debian from any stock install medium on a non-optical medium (e.g. usb stick, HDD), it's necessary to use a different initramfs instead of the default one on the installation medium which is located at `(loop)/install.amd/initrd.gz`. If you boot with the default one, the installer will unable to find or mount the proper iso image for installation. Please download the initramfs for hard disk installation from an official mirror site, put it in the same directory with the image file and give it a suitable name (`debian-7.8.0-amd64-DVD-1.hdd.initrd.gz` in this example).

    menuentry '[loopback]debian-7.8.0-amd64-DVD-1' {
    	set isofile='/boot/iso/debian-7.8.0-amd64-DVD-1.iso'
    	set initrdfile='/boot/iso/debian-7.8.0-amd64-DVD-1.hdd.initrd.gz'
    	loopback loop $isofile
    	linux (loop)/install.amd/vmlinuz vga=791 iso-scan/ask_second_pass=true iso-scan/filename=$isofile
    	initrd $initrdfile
    }

##### Live install medium

- Initramfs framework: initramfs-tools (cmdline: RFD)
- Live framework: Debian Live (cmdline: [13])
- Init system: sysvinit (cmdline: RFD)

    menuentry '[loopback]debian-live-7.8.0-amd64-xfce-desktop' {
    	set isofile='/boot/iso/debian-live-7.8.0-amd64-xfce-desktop.iso'
    	loopback loop $isofile
    	linux (loop)/live/vmlinuz boot=live config fromiso=/dev/sdb2/$isofile
    	initrd (loop)/live/initrd.img
    }

Note: It's also OK to use `findiso=$isofile` instead of the longer `fromiso=/dev/disk/by-.../.../$isofile`. Anyway, using `fromiso=` instead of `findiso=` may speed up the initialization progress because it avoids unnecessary mounting.

#### Elementary OS

- Initramfs framework: RFD
- Live framework or installation program: RFD
- Init system: upstart (cmdline: RFD)

    menuentry '[loopback]elementaryos-freya-amd64.20150411' {
    	set isofile='/boot/iso/elementaryos-freya-amd64.20150411.iso'
    	loopback loop $isofile
    	linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile locale=en_US.UTF-8
    	initrd (loop)/casper/initrd.lz
    }

#### Fedora

##### Stock installation medium

- Initramfs framework: Dracut (cmdline: [14])
- Installation program: Anaconda (cmdline: [15])
- Init system: systemd (cmdline: [16])

    menuentry '[loopback]Fedora-Workstation-netinst-x86_64-24-1.2' {
    	set isofile='/boot/iso/Fedora-Workstation-netinst-x86_64-24-1.2.iso'
    	loopback loop $isofile
    	linux (loop)/isolinux/vmlinuz inst.stage2=hd:LABEL=Fedora-WS-dvd-x86_64-24 iso-scan/filename=$isofile quiet
    	initrd (loop)/isolinux/initrd.img
    }

##### Workstation live medium

- Initramfs framework: Dracut (cmdline: [17])
- Live framework: fedora livecd-tools (cmdline: none)
- Init system: systemd (cmdline: [18])

    menuentry '[loopback]Fedora-Workstation-Live-x86_64-24-1.2' {
    	set isofile='/boot/iso/Fedora-Workstation-Live-x86_64-24-1.2.iso'
    	loopback loop $isofile
    	linux (loop)/isolinux/vmlinuz root=live:CDLABEL=Fedora-WS-Live-24-1-2 iso-scan/filename=$isofile rd.live.image quiet
    	initrd (loop)/isolinux/initrd.img
    }

#### Gentoo

##### Desktop LiveDVD

- Initramfs framework: genkernel (cmdline: [19])
- Live framework: livecd-tools (cmdline: RFD)
- Init system: OpenRC (cmdline: RFD)

    menuentry "[loopback]livedvd-amd64-multilib-20160514" {
    	set isofile="/boot/iso/livedvd-amd64-multilib-20160514.iso"
    	loopback loop $isofile
    	linux (loop)/isolinux/gentoo root=/dev/ram0 init=/linuxrc aufs looptype=squashfs loop=/image.squashfs cdroot isoboot=$isofile vga=791 splash=silent,theme:default console=tty0
    	initrd (loop)/isolinux/gentoo.xz
    }

Tip: This should also works for minimal medium.

#### GParted Live

- Initramfs framework: initramfs-tools (cmdline: RFD)
- Live framework: Debian Live (cmdline: [20])
- Init system: sysvinit (cmdline: RFD)

    menuentry "[loopback]gparted-live-0.22.0-2-amd64" {
    	set isofile="/boot/iso/gparted-live-0.22.0-2-amd64.iso"
    	loopback loop $isofile
    	linux (loop)/live/vmlinuz boot=live union=overlay username=user config components quiet noswap noeject toram=filesystem.squashfs ip=  nosplash findiso=$isofile
    	initrd (loop)/live/initrd.img
    }

#### Kali Linux

- Initramfs framework: initramfs-tools (cmdline: RFD)
- Live framework: Debian Live (cmdline: [21])
- Init system: sysvinit (cmdline: RFD)

    menuentry "[loopback]kali-linux-1.0.7-amd64" {
    	set isofile='/boot/iso/kali-linux-1.0.7-amd64.iso'
    	loopback loop $isofile
    	linux (loop)/live/vmlinuz boot=live findiso=$isofile noconfig=sudo username=root hostname=kali
    	initrd (loop)/live/initrd.img
    }

#### Knoppix

- Initramfs framework: Unknown
- Live framework: Unknown
- Init system: Unknown

    menuentry "[loopback]KNOPPIX_V7.4.2DVD-2014-09-28-EN" {
            set isofile="/boot/iso/KNOPPIX_V7.4.2DVD-2014-09-28-EN.iso"
            loopback loop $isofile
            linux (loop)/boot/isolinux/linux bootfrom=/mnt-iso/$isofile acpi=off keyboard=us lang=us
            initrd (loop)/boot/isolinux/minirt.gz
    }

#### Linux Mint

- Initramfs framework: RFD
- Live framework or installation program: RFD
- Init system: RFD

    menuentry "Linux Mint 17.2 Cinnamon LTS RC (x64)" {
        set iso=/boot/iso/linuxmint-17.2-cinnamon-64bit.iso
        loopback loop $iso
        linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$iso noeject noprompt
        initrd (loop)/casper/initrd.lz
    }

#### openSUSE

##### Stock installation medium

- Initramfs framework: RFD
- Live framework or installation program: Kiwi? RFD
- Init system: RFD

    menuentry '[loopback]openSUSE-13.1-DVD-x86_64' {
    	set isofile='/boot/iso/openSUSE-13.1-DVD-x86_64.iso'
    	loopback loop $isofile
    	linux (loop)/boot/x86_64/loader/linux install=hd:$isofile
    	initrd (loop)/boot/x86_64/loader/initrd
    }

##### Desktop Live medium

- Initramfs framework: RFD
- Live framework or installation program: Kiwi? RFD
- Init system: RFD

    menuentry '[loopback]openSUSE-13.1-KDE-Live-x86_64' {
    	set isofile='/boot/iso/openSUSE-13.1-KDE-Live-x86_64.iso'
    	loopback loop $isofile
    	linux (loop)/boot/x86_64/loader/linux isofrom_device=$imgdevpath isofrom_system=$isofile LANG=en_US.UTF-8
    	initrd (loop)/boot/x86_64/loader/initrd
    }

#### Parabola GNU/Linux-libre

Tip: If you want to boot into a 32-bit system, replace `x86_64` with `i686`.

    menuentry '[loopback]parabola-2015.07.01-dual.iso' {
    	set isofile='/boot/iso/parabola-2015.07.01-dual.iso'
    	loopback loop $isofile
    	linux (loop)/parabola/boot/x86_64/vmlinuz parabolaisolabel=PARA_201507 img_dev=$imgdevpath img_loop=$isofile earlymodules=loop
    	initrd (loop)/parabola/boot/x86_64/parabolaiso.img
    }

Tip: The label string after `parabolaisolabel=` needs to be edited when a newer release is used.

#### Sabayon

- Initramfs framework: genkernel? RFD
- Live framework or installation program: RFD
- Init system: openrc? RFD

    menuentry '[loopback]Sabayon_Linux_14.05_amd64_KDE' {
    	set isofile='/boot/iso/Sabayon_Linux_14.05_amd64_KDE.iso'
    	loopback loop $isofile
    	linux (loop)/boot/sabayon root=/dev/ram0 aufs cdroot locale=en_US loop=/livecd.squashfs looptype=squashfs isoboot=$isofile
    	initrd (loop)/boot/sabayon.igz
    }

#### Slackware Linux

- Initramfs framework: RFD
- Live framework or installation program: RFD
- Init system: RFD

    menuentry '[loopback]slackware64-14.1-install-dvd' {
    	set isofile='/boot/iso/slackware64-14.1-install-dvd.iso'
    	loopback loop $isofile
    	linux (loop)/kernels/huge.s/bzImage printk.time=0
    	initrd (loop)/isolinux/initrd.img
    }

#### SystemRescueCD

- Initramfs framework: RFD
- Live framework or installation program: RFD
- Init system: RFD

Note: Replace `64` with `32` if you want to boot into a 32-bit system.

    menuentry '[loopback]systemrescuecd-x86-4.5.2' {
    	set isofile='/boot/iso/systemrescuecd-x86-4.5.2.iso'
    	loopback loop $isofile
    	linux (loop)/isolinux/rescue64 isoloop=$isofile
    	initrd (loop)/isolinux/initram.igz
    }

#### Slitaz

- Initramfs framework: RFD
- Live framework: RFD
- Init system: RFD

First, download slitaz iso, then extract somewhere (in this case, /live/slitaz-4.0 on /dev/sda3)

    menuentry 'slitaz-4.0 core' {
    	set dir='/live/slitaz-4.0'
    	set root=(hd0,msdos3)
    	set lang='pt_BR'
    	set kmap='br-abnt2'
    	linux ($root)/$dir/bzImage lang=$lang kmap=$kmap rw root=/dev/null vga=normal autologin
    	initrd ($root)/$dir/rootfs4.gz ($root)/$dir/rootfs3.gz ($root)/$dir/rootfs2.gz ($root)/$dir/rootfs1.gz
    }

#### Slax

- Initramfs framework: RFD
- Live framework: RFD
- Init system: RFD

First, download Slax zip (for USB), then extract somewhere (in this case, /live/slax on /dev/sda3)

    menuentry 'slax' {
    	set dir=/live/slax
    	set root=(hd0,msdos3)
    	linux $dir/boot/vmlinuz from=$dir vga=normal load_ramdisk=1 prompt_ramdisk=0 printk.time=0 slax.flags=perch,xmode
    	initrd $dir/boot/initrfs.img
    }

#### Tails

- Initramfs framework: Unknown
- Live framework: Unknown
- Init system: Unknown

Simply download and verify integrity of the Tails iso.

    menuentry "[loopback]tails-i386-1.5.iso" {
        set isofile='/boot/iso/tails-i386-1.5.iso'
        loopback loop $isofile
        linux (loop)/live/vmlinuz2 boot=live config findiso=${isofile} live-media=removable apparmor=1 security=apparmor nopersistent noprompt timezone=Etc/UTC block.events_dfl_poll_msecs=1000 noautologin module=Tails
        initrd (loop)/live/initrd2.img
    }

Warning: Emergency memory erasure does not seem to work when booting this way.

Remove the `live-media=removable` option if the iso file is not on removable media.

#### Ubuntu

- Initramfs framework: RFD
- Live framework or installation program: RFD
- Init system: upstart (cmdline: RFD)

    menuentry '[loopback]ubuntu-14.04.1-desktop-amd64' {
    	set isofile='/boot/iso/ubuntu-14.04.1-desktop-amd64.iso'
    	loopback loop $isofile
    	linux (loop)/casper/vmlinuz.efi boot=casper iso-scan/filename=$isofile locale=en_US.UTF-8
    	initrd (loop)/casper/initrd.lz
    }

#### Xubuntu (32 bit)

    menuentry '[loopback]Xubuntu-16.04-desktop-i386' {
    	set isofile='/boot/iso/xubuntu-16.04-desktop-i386.iso'
    	loopback loop $isofile
    	linux	(loop)/casper/vmlinuz  file=/cdrom/preseed/xubuntu.seed boot=casper iso-scan/filename=$isofile quiet splash ---
    	initrd	(loop)/casper/initrd.lz
    }

## Chainloading Windows

It can be very difficult to loopback a Windows install disc. One simple solution that allows you to install a variety of platforms from a USB drive with a single, unified partition is to start with a working, bootable Windows USB drive, and to replace its bootloader with GRUB.

Before installing GRUB, rename or move the Windows bootloader. It should be the default .efi executable - located at `(USB)/efi/boot/bootx64.efi` for a 64-bit system. Install GRUB in its place, and ensure that it is now the default executable.

You can then chainload the renamed Windows bootloader from GRUB, and also configure GRUB to loopback .iso files as described above.

    menuentry '[chain]en_windows_8.1_professional_x64' {
    	insmod chain
            chainloader /efi/boot/bootx64.efi.windows
    }

## Using Syslinux and memdisk

Using the memdisk module, the ISO image is loaded into memory, and its bootloader is loaded. Make sure that the system that will boot this USB drive has sufficient amount of memory for the image file and running operating system.

### Preparation

Make sure that the USB drive is properly partitioned and that there is a partition with file system supported by Syslinux, for example fat32 or ext4. Then install Syslinux to this partition, see Syslinux#Installation[broken link: invalid section].

### Install the memdisk module

The memdisk module was not installed during Syslinux installation, it has to be installed manually. Mount the partition where Syslinux is installed to `/mnt/` and copy the memdisk module to the same directory where Syslinux is installed:

    # cp /usr/lib/syslinux/bios/memdisk /mnt/boot/syslinux/

### Configuration

After copying the ISO files on the USB drive, edit the Syslinux configuration file and create menu entries for the ISO images. The basic entry looks like this:

    boot/syslinux/syslinux.cfg

    LABEL some_label
        LINUX memdisk
        INITRD /path/to/image.iso
        APPEND iso

See memdisk on Syslinux wiki for more configuration options.

### Caveat for 32-bit systems

When booting a 32-bit system from an image larger than 128MiB, it is necessary to increase the maximum memory usage of vmalloc. This is done by adding `vmalloc=valueM` to the kernel parameters, where `value` is larger than the size of the ISO image in MiB.[22]

For example when booting the 32-bit system from the Arch installation ISO, press the `Tab` key over the `Boot Arch Linux (i686)` entry and add `vmalloc=768M` at the end. Skipping this step will result in the following error during boot:

    modprobe: ERROR: could not insert 'phram': Input/output error

## See also

- GRUB:
  - https://help.ubuntu.com/community/Grub2/ISOBoot/Examples
  - https://help.ubuntu.com/community/Grub2/ISOBoot
- Syslinux:
  - Boot an ISO image

Category:

- Boot process

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