feature request: automatic detection of root device

[sewnie]

would this be possible?

also:
since root device can be automatically detected, so can the file system module for it.

this could allow for configuration-less tinyramfs.

[illiliti]

It is possible, but that would be unreliable.

root device autodetection implies that we have to iterate over disk devices, mount them and then check /sbin/init. if it exist - switch_root into it, if not - continue.

It is unreliable because mount can fail due to fs module not being loaded. mount can also fail because disk device could be encrypted, so have to implement fs type checking. There're also more complex file systems like zfs or btrfs, which may have nested file systems/partitions/pools...

This is pretty hard to do properly. I'd rather have only static configuration defined by user. This is more reliable than being too smart and autodetect everything.

since root device can be automatically detected, so can the file system module for it.

Tinyramfs already autodetects filesystem module for rootfs:

tinyramfs/tinyramfs

Lines 112 to 120 in 6b9f73d

	if [ "$root_type" ]; then
	copy_kmod "$root_type"
	else
	while read -r _ _dir _type _; do
	[ "$_dir" = / ] && break
	done < /proc/mounts || panic 'unable to detect rootfs module'
	copy_kmod "$_type"
	fi

But again, it is unreliable. It might be removed in the future because it doesn't work in live usb environment and environment where /proc isn't mounted.

[sewnie]

not exactly what i meant, what i meant was that at configuring time when tinyramfs is building the initramfs. i wouldn't think this is that hard because it can simply check what device is /.