yastfli (Yet Another Script To Flash LiveOS ISOs)

Introduction

yastfli, pronounced just fly, is a simple script that copies Fedora Live ISOs to USB memory sticks or external drives and adds an overlay for persistent storage. It supports ext4 and FAT32 for the data partition, as well as image or directory overlays for ext4.

I started writing yastfli after investigating why livecd-iso-to-disk had not been fully functional since Fedora 37 [1][2][3][4]. This is not an attempt to replace livecd-iso-to-disk, which offers many features beyond what I intend to add to yastfli. However, possibly due to its inherent complexity, no one has stepped up to fix it so far. This has led to several community efforts, including this one, to create a simpler script that can at least add an overlay for persistent storage to Fedora Live images.

• [1] https://bugzilla.redhat.com/show_bug.cgi?id=2180524
• [2] https://bugzilla.redhat.com/show_bug.cgi?id=2152842
• [3] livecd-tools/livecd-tools#253
• [4] livecd-tools/livecd-tools#262

How to use yastfli

In normal mode, yastfli destroys all existing data on the target drive.
If you need a tool that preserves existing data while adding a new Live OS, yastfli is not suitable.
If you are unsure what that means, this tool is probably not for you either.
It only takes one moment of confusion between /dev/sda and /dev/sdb to wipe your hard drive and cause serious data loss.

With that disclaimer out of the way, let's take a quick look at the help option.

 SYNTAX

 (sudo) yastfli [options] --iso <path> --target <device>

 OPTIONS

 --directory|-d
   Use a directory overlay instead of an image file.
   Cannot be used with FAT32. The size option is ignored.
   Default: false.

 --filesystem|-f [ext4|fat32]
   Filesystem of the data partition.
   Default: ext4.

 --iso|-i
   Path to the Live ISO file.

 --label|-l
   Label of the data partition.
   Default: LIVE.

 --no-overlay|-n
   Do not create an overlay.
   Default: false.

 --preserve|-p
   Do not format EFI and data partitions.
   Deletes EFI, images, and LiveOS folders instead. Deletes overlay.
   Default: false.

 --size-mb|-s
   Size in MB of the overlay file.
   Cannot exceed 4095 for FAT32 data partitions.
   Default: 512.

 --target|-t
   Target device, e.g. /dev/sda.

 --help|-h
   Display this help message.

You will need root access, or the ability to run yastfli with sudo. At a minimum, you must provide the path to the ISO file and the target device.

sudo ./yastfli -i path/to/ISO -t /dev/sdX

If no other arguments are provided, yastfli will use ext4 for the data partition and create a 512M overlay image.

To create a larger overlay image, use the -s option:

sudo ./yastfli -i path/to/ISO -t /dev/sdX -s 2048

To use FAT32 instead of ext4 for the data partition, use -f fat32. The overlay image will be limited to 4095M, and a directory overlay cannot be used:

sudo ./yastfli -i path/to/ISO -t /dev/sdX -s 2048 -f fat32

To use a directory overlay, the data partition must be ext4 (the default). Enable it with -d:

sudo ./yastfli -i path/to/ISO -t /dev/sdX -d

To skip creating any overlay, use -n. Any overlay-related options provided in error will be ignored:

sudo ./yastfli -i path/to/ISO -t /dev/sdX -n

To set a custom label for the data partition, use -l mylabel. This option works with all other options, but note that the label is not sanitised to comply with filesystem requirements:

sudo ./yastfli -i path/to/ISO -t /dev/sdX -l MY_LABEL

Preserve mode

While --preserve (-p) is just another option like those above, it requires further explanation, so it has its own section.

Disclaimer: You should not use yastfli with any device containing data you cannot afford to lose. This includes using the preserve option, as things can still go wrong from time to time.

In normal mode, yastfli formats the entire target device and creates two partitions: an EFI partition and a data partition.
The preserve option skips formatting and instead deletes the EFI and images folders on the EFI partition, as well as the LiveOS folder on the data partition, which contains the overlay, whether it is a file overlay or a directory overlay.

The preserve feature assumes that you have already created a bootable LiveOS device with yastfli and only want to refresh the image without deleting files or folders on the data partition outside the LiveOS structure.

With this in mind, options like --filesystem (-f) or --label (-l) are irrelevant when using preserve, as they only apply when formatting. You also cannot use a directory overlay if the data partition is FAT32.

To use the preserve option, simply add it to the command line:

sudo ./yastfli -i path/to/ISO -t /dev/sdX -p

You can combine it with some other options, such as a directory overlay on ext4:

sudo ./yastfli -i path/to/ISO -t /dev/sdX -p -d

Or specify a custom overlay size:

sudo ./yastfli -i path/to/ISO -t /dev/sdX -p -s 2048

Does yastfli work with other distributions?

yastfli can write OpenSUSE Live images, but they do not boot. Ubuntu uses a very different structure, and there are other tools better suited for it.

In summary, it may be possible to write some other distributions, but it is unlikely to result in a bootable Live OS with a persistent overlay.