Syslinux - Apr 2020 - Installing extlinux into a disk image without being root?

Hello,

Is it possible to install extlinux into a disk image, without being
root ?

It seems like extlinux --install absolutely requires the specific block
device in which extlinux should be installed to be mounted. This
prevents from doing an extlinux installation as non-root, which is
annoying for build systems such as Buildroot [1] that build a complete
Linux system from source, without being root, and aim at producing
ready to flash disk images, also without being root.

I have tried:

  extlinux --device disk.img --install boot/extlinux

but extlinux complains:

./output/host/sbin/extlinux: path boot/extlinux/ doesn't match device
disk.img

Am I missing something in what options we have to install extlinux ?

Thanks,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

> Is it possible to install extlinux into a disk image, without being
> root ?
> 
> It seems like extlinux --install absolutely requires the specific block
> device in which extlinux should be installed to be mounted. This
> prevents from doing an extlinux installation as non-root, which is
> annoying for build systems such as Buildroot [1] that build a complete
> Linux system from source, without being root, and aim at producing
> ready to flash disk images, also without being root.
> 
> I have tried:
> 
>   extlinux --device disk.img --install boot/extlinux
> 
> but extlinux complains:
> 
> ./output/host/sbin/extlinux: path boot/extlinux/ doesn't match device
disk.img
> 
> Am I missing something in what options we have to install extlinux ?
 
 
I think that you are misusing the options.

Depending on what exactly "disk.img" actually is, you _might_
(perhaps) get to
install the bootloader by means of other options.

As of not using "root" privileges, there is the
"syslinux-mtools" (aka
"mtools/syslinux") installer, but it also depends on what exactly
"disk.img"
actually is.

Please see the "Install" wiki page in the Syslinux wiki.

Additionally, some Linux distributions have additional features incorporated in 
some of their "Syslinux-related" installers.

Regards,
Ady.

Hello,

Thanks for your feedback!

On Thu, 16 Apr 2020 11:02:41 +0300
Ady via Syslinux <syslinux at syslinux.org> wrote:
> I think that you are misusing the options.
> 
> Depending on what exactly "disk.img" actually is, you _might_
(perhaps) get to
> install the bootloader by means of other options.
disk.img is a disk image, which contains a partition table, itself
describing one partition, formatted ext4, with a Linux root filesystem.
> As of not using "root" privileges, there is the
"syslinux-mtools" (aka
> "mtools/syslinux") installer, but it also depends on what exactly
"disk.img"
> actually is.
> 
> Please see the "Install" wiki page in the Syslinux wiki.
If I understand correctly this page, mtools/syslinux only supports FAT
filesystems (which makes sense since mtools are FAT-related). And
extlinux does require the filesystem to be mounted, which requires root
privileges.

Correct?

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com