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Instructions to make a boot drive, that boots both in UEFI and BIOS mode

Cloning - read-only drive

If you are happy with a read-only partition table and file system, you can clone the Ubuntu and Ubuntu community flavour iso files. This is very reliable but you cannot store data on the drive, and you cannot make it a persistent live drive (unless you start again for example with mkusb). Return if this is what you want.

Do it yourself - with the extraction method

The simple extraction method for UEFI mode is extended to BIOS mode and described with detailed instructions.

This method is designed to work with

• Ubuntu: 64-bit Ubuntu desktop and Ubuntu community flavour desktop iso files

• Debian live (version 10--11) 64-bit iso files

• Windows: 64-bit Windows (8--11) iso files

  • Windows 7 boots only in BIOS mode

  • Several Windows 10 all Windows 11 iso files and contain a version of the file install.wim with size > 4 GiB. It means that this method does not work because the FAT32 file system cannot manage it. There is a detailed description of a modified method at this link: /windows-installer-for-big-files See also this link.

Other linux distros and versions: This method may or may not work in UEFI and/or BIOS mode depending on the boot structure. It helps if it is similar to Ubuntu's boot structure.

• Linux Mint: From 'linuxmint-18.1-cinnamon-64bit.iso' you get a USB drive that boots in UEFI and BIOS mode, and you can make it persistent live.
• Debian 9, Stretch: From 'debian-live-9.0.1-amd64-cinnamon.iso', you get a USB drive that boots only in BIOS mode. The structure for booting and persistence is different from Ubuntu. (A cloned live-only USB drive can boot in UEFI and BIOS mode; If you wish, mkusb can create a USB drive that boots in UEFI and BIOS mode, and make it persistent live.)

Do it yourself - instructions

Download a compressed image file

You need this step only if you want to boot in BIOS mode

An extracted system boots directly in UEFI mode. When this is enough, you need no bootloader for BIOS mode, but it is also a convenient method to get the partition table and boot structure.

Partition table and boot structure from an image file

A compressed image file can be extracted and flashed to the target drive in order to get partition table and the boot structure necessary for booting via grub in BIOS mode. This works also when you are running an installed system booted in UEFI mode, when there are problems to install 'grub-pc' and run 'grub-install' in order to install the bootloader (for BIOS mode).

Do also this step manually

Otherwise, in BIOS mode and running a live system, it is possible to create the boot structure for BIOS mode with a FAT32 partition and extract from the iso file into it and install the bootloader.

sudo grub-install

So if you want to do also this step yourself, boot in BIOS mode and create it. You may need to add some flags to the FAT32 partition to make a computer want to boot into it also in UEFI mode.

The structure created, when you use the compressed image file can be used to check what you need in order to get a system that works in both boot modes. (This is easiest, if you have two USB pendrives, one where you do it yourself, and one with the extracted partition table and boot structure.)

Download the image file and a checksum file

You may want a higher level of security. This file is signed with gpg and you can verify it according to the following commands.

gpg --keyserver keyserver.ubuntu.com --recv-keys EB0FC2C8
gpg --verify grub-do-it-yourself.img.xz.md5.asc 

The warning "was NOT verified" means that there is no chain of trusted keys between your computer's keyring and the key, that was used to sign the checksums (the key of sudodus). Check that the result matches with the following output, when you verify it,

tester@xenial32 ~ $ gpg --keyserver keyserver.ubuntu.com --recv-keys EB0FC2C8
gpg: directory `/home/tester/.gnupg' created
gpg: new configuration file `/home/tester/.gnupg/gpg.conf' created
gpg: WARNING: options in `/home/tester/.gnupg/gpg.conf' are not yet active during this run
gpg: keyring `/home/tester/.gnupg/secring.gpg' created
gpg: keyring `/home/tester/.gnupg/pubring.gpg' created
gpg: requesting key EB0FC2C8 from hkp server keyserver.ubuntu.com
gpg: /home/tester/.gnupg/trustdb.gpg: trustdb created
gpg: key EB0FC2C8: public key "Nio Sudden Wiklund (sudodus) <address@mailserver.com>" imported
gpg: no ultimately trusted keys found
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)

tester@xenial32 ~ $ gpg --verify grub-do-it-yourself.img.xz.md5.asc
gpg: Signature made mån 18 sep 2017 21:48:47 CEST using RSA key ID EB0FC2C8
gpg: Good signature from "Nio Sudden Wiklund (sudodus) <nio.wiklund@gmail.com>"
gpg: WARNING: not a detached signature; file 'grub-do-it-yourself.img.xz.md5' was NOT verified!
tester@xenial32 ~ $ 

Then there is reason to trust that nobody else has written the checksums. The date of the signature will change at updates, and the text might be translated to your local language, but it should be clear that it is a 'Good signature from "Nio Sudden Wiklund (sudodus)"'.

If you have the compressed image file and the md5sum file in the same directory, you can use the md5sum program to check like this,

tester@xenial32 ~ $ md5sum -c grub-do-it-yourself.img.xz.md5.asc
grub-do-it-yourself.img.xz: OK
md5sum: WARNING: 14 lines are improperly formatted

The 'improperly formatted lines' are the lines belonging to the gpg signature.

Download the iso file

64-bit Ubuntu desktop or Ubuntu community flavour desktop iso file

http://releases.ubuntu.com or for the community flavours http://cdimage.ubuntu.com

If the iso files of the version with the longest remaining support are not found via those links, you can find them via the following general link,

http://old-releases.ubuntu.com

and right now, when this is written, you want to find Ubuntu 16.04.1 LTS via the following link,

http://old-releases.ubuntu.com/releases/xenial

or

64-bit Debian live iso file

You find current Debian iso files via www.debian.org/CD/live/

or

64-bit Windows 7--11 iso file

You find Windows iso files via Microsoft's web pages (and you need a license key to use it later on).

Check with md5sum that the iso file was downloaded correctly

Examples:

Create mountpoint /mnt/lp1

sudo mkdir -p /mnt/lp1

Loop mount the iso file

for example

sudo mount -o loop ubuntu-22.04.1-desktop-amd64.iso /mnt/lp1
sudo mount -o loop Win10_US_x64.iso /mnt/lp1

In a Windows iso file, check the size of the biggest file

When you have loop mounted a Windows iso file, you should check the size of the biggest file, often '''install.wim'''. If it is > 4GiB, you need an ntfs partition. You can look for the biggest file with the following command line,

find /mnt/lp1 -ls|sort -nk7|tail -n1

Convert from bytes to MiB (you can divide by 2^30 in bc).

You can find all files that exceed the limit directly with the following command line,

find /mnt/lp1 -size +4G -printf "%11s %p\n" | sort -n

If a file in the iso file exceeds 4 GiB

If a file exceeds the limit, you should download and use another compressed image file, that provides two partitions, one with the file system FAT16 and one with NTFS, that can manage the big file.

Install mkusb if you want to clone safely and easily (optional)

https://help.ubuntu.com/community/mkusb

Clone 'grub-do-it-yourself.img.xz' to the target drive

Use mkusb or Disks

dus grub-do-it-yourself.img.xz

or

Use dd to clone in a risky way

Identify the target drive. You can use lsblk without options or better, copy and paste the following command line

lsblk -d -o name,vendor,model,type,size,hotplug

Make sure there are no mounted partitions in the target drive

where X is the drive letter of the target drive, and then use the correct drive letter in the cloning command line

where X is the drive letter of the target drive. Check that the drive letter is correct, and double-check the details of the whole command line. A minor typing error might overwrite your family pictures.

Flush the buffers and inform the kernel of the new partition table

Use Win32 Disk Imager to clone in Windows

Mount the target drive

Create mountpoint and /mnt/sd1

sudo mkdir -p /mnt/sd1

Mount the partition on the USB pendrive or memory card

Identify the target drive. You can use lsblk without options or better, copy and paste the following command line

lsblk -d -o name,vendor,model,type,size,hotplug

or blkid, grep and cut, copy and paste the following command line

sudo blkid |grep DIDITMYSELF|cut -d ' ' -f 1-2

and then use the correct drive letter in the mounting command line

where X is the drive letter of the target drive. Double-check that the drive letter is correct.

Copy the content from the iso file to the target partition

rsync

There may be some warning and error messages from the rsync copying process. Some links cannot be understood and some permissions cannot be preserved by the FAT32 file system in the target partition. But the result will still be a useful system in the drive.

But I have seen cases, when running in some versions of 32-bit Ubuntu systems, where rsync does not copy all the files correctly. They are truncated (too small). When this happens the system in the drive will not work. rsync did not notice it; there was no warning or error message about this problem.

Alternative 1

Alternative 2

You can try to extract the content from the iso file to the target partition with your favourite tool for compressed files, for example

Flush the buffers

Now you have a live-only boot drive :-)

Unmount the partition on the target drive and unplug it

Check that no partition on the target drive is mounted with

(and you can unmount the iso file too

sudo umount /mnt/lp1

but it is mounted read-only, and not dangerous to leave mounted)

or

Continue if you wish

Create a new partition for storage

If there is space enough (if the drive contains more than 8 GB), create a second partition. It is easy to use gparted to create the second partition.

Make an Ubuntu persistent live drive

casper-rw file

(The old method for persistence is a file system in a file. Today it is usually better to use a partition for persistence.)

Create a file with the name 'casper-rw'. There is free space in the FAT32 partition for the maximum 4 GB size. The partition must be mounted.

sudo mount /dev/sdX1 /mnt/sd1  # replace X with the actual drive letter like you did before
sudo dd if=/dev/zero of=/mnt/sd1/casper-rw bs=1M count=4095

and create an 'ext2' file system inside the file

sudo mkfs.ext2 /mnt/sd1/casper-rw

Alternative - sharing free space between 'casper-rw' and 'home-rw'

You can use almost all (say 95%) of the remaining free space shared between a 'casper-rw' file and a 'home-rw' file. Decide how much to use for each of them depending on how you intend to use the drive: to install programs and/or to store data.

casper-rw partition

If you have a USB pendrive (or memory card or SSD via USB adapter), that is bigger than 8 GB, it can be better to use a partition for persistence. This way you can use the whole drive. It works with

• Ubuntu 19.10
• Debian 10 live

and we expect that it will work with newer versions of Ubuntu and Debian.

Again check carefully that you create the partition for persistence in the correct drive X.

sudo fdisk /dev/sdX
n
<press the Enter key>
<press the Enter key>
<press the Enter key>
w

and create an 'ext2' file system in the partition

sudo mkfs.ext2 -L casper-rw /dev/sdX2

You can also use gparted to create the second partition. In that case, remember the label casper-rw.

There is an obvious advantage with journaling: the file system will be more robust. So if you think your system will be responsive enough, and you can accept more wear, create an ex4 file system with mkfs.ext4 instead of the ext2 file system.

Let Ubuntu create the partition for persistence automatically

In Ubuntu 19.10 with the system files in a FAT32 partition, if you create

• neither a casper-rw file
• nor a casper-rw partition,
• and there is space available in the USB drive,

the Ubuntu system (I think software in the package 'casper') will do it for you the first time that you boot into the USB drive.

This will happen even if you don't add the boot option 'persistent', which might be irritating, but it can also be very useful, because it makes it easier to create a working persistent live system in Windows.

I noticed that the file system ext4 with journaling was created automatically. Due to journaling it can make the system slow, particularly if the USB drive is slow. You can tweak ext4 by turning off journaling or use the simpler ext2 which lacks journaling. You will also reduce wear when there is no journaling (with ext2 or with ext4 with journaling turned off).

There is an obvious advantage with journaling: the file system will be more robust. So if you think your system will be responsive enough, let Ubuntu create the partition for persistence automatically and keep journaling.

Edit grub.cfg

The first partition must be mounted.

sudo mount /dev/sdX1 /mnt/sd1  # replace X with the actual drive letter like you did before

linux ... quiet splash persistent ---

and if there is enough RAM in the computer(s) you can copy the content of the iso file to RAM with the boot option toram

linux ... quiet splash persistent toram ---

You may want an extra menuentry for maintenance (backup and repair) of your casper-rw partition.

• copy the menuentry, that you edited

• modify it to have the boot option nopersistent and maybe toram

linux ... quiet splash nopersistent ---

Save the edited file and exit from the editor

Now you have a drive with a second partition and/or persistence :-)

Now you have a drive with a second partition for storage in Ubuntu and the Ubuntu community flavours. Windows can use the first partition (and if the second partition is a Microsoft file system, FAT32 or NTFS, an up to date Windows 10 system can use the second partition too).

Or you have persistence via the casper-rw file, or both.

Unmount the mounted partition on the target drive and unplug it

sudo umount /mnt/sd1

Check that no partition on the target drive is mounted with

df

(and you can unmount the iso file too

sudo umount /mnt/lp1

but it is mounted read-only, and not dangerous to leave mounted).

Persistence with Debian 10 live

partition for persistence

If you have a USB pendrive (or memory card or SSD via USB adapter), that is bigger than 8 GB, it can be better to use a partition for persistence. This way you can use the whole drive. It works with Debian 10 live, "Buster", and we expect that it will work with newer versions.

Again check carefully that you create the partition for persistence in the correct drive X.

sudo fdisk /dev/sdX
n
<press the Enter key>
<press the Enter key>
<press the Enter key>
w

and create an 'ext2' file system in the partition

sudo mkfs.ext2 -L persistence /dev/sdX2

Edit grub.cfg

The first partition must be mounted.

sudo mount /dev/sdX1 /mnt/sd1  # replace X with the actual drive letter like you did before

Edit the file /mnt/sd1/boot/grub/grub.cfg to add the boot option 'persistence' to the line starting with linux

linux ... quiet splash persistence ---

Create persistence.conf

Create a mountpoint

sudo mkdir /mnt/sd2

Mount the new partition

sudo mount /dev/sdX2 /mnt/sd2

and write a configuration file into it

sudo bash -c 'echo / union > /mnt/sd2/persistence.conf'

Flush the buffers, inform the kernel and unmount the partitions

sync
sudo partprobe
sudo umount /mnt/sd1 /mnt/sd2 /mnt/lp1

Check that your new boot drive works

Check that your new boot drive works as expected, and if not, try again, maybe you missed a step ...

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