Hi, > On August 9, 2018 at 9:45 AM Giorgio Dal Molin <giorgio.nicole@xxxxxxxx> wrote: > > > Hi, > > > On August 8, 2018 at 9:52 AM Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> wrote: > > > > > > On Tue, Jul 31, 2018 at 01:20:12PM +0200, Giorgio Dal Molin wrote: > > > Hi all, > > > > > > I'm trying to find out the best method to define the root= > > > parameter when booting the linux kernel from barebox. > > > > > > My system boots from an sd card partitioned with a GPT. > > > The sd card has two independent set of partitions with > > > the following labels: > > > > > > 1) boot_1 + rootfs_1 > > > 2) boot_2 + rootfs_2 > > > > > > for redondance in case one set gets damaged while updating. > > > > > > 'boot_1' is formatted with ext4 and contains the kernel + dtb images > > > for the userland in 'rootfs_1'; and the same for 'boot_2' and 'rootfs_2'. > > > > > > Currently I hardcode the 'root' parameter to '/dev/mmcblk0p3' or > > > '/dev/mmcblk0p4' corresponding to the kernel in 'boot_1' or > > > 'boot_2' and it actually works but is there a better way to do > > > this ? > > > > You could use bootloader spec. That would at least allow you to store a > > suitable root= parameter in the config files in the boot_1 and boot_2 > > partitions. > > > > Not sure if that's what you are looking for though. > > > > Sascha > > > > as I already wrote to Uwe Kleine-Koenig I wanted to keep the kernel > image and the dtb in a separate partition because these are the files > the bootloader *must* be able to read to boot the system. Having the > userland in a separate partition lets me choose an image format for it > independently from what barebox supports; as an example I could pack > my userland in a btrfs image. Moreover I can be more selective when > updating the firmware: I can update only the kernel+dtb or only the > userland image. > > What I would like to have is an automatic way to set the root= kernel > command line parameter similar to what barebox does with the 'bootm.appendroot' > but a bit more flexible. > Looking at the kernel function name_to_dev_t() in the source init/do_mounts.c, > it accepts also the format 'PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF': > my idea was to somehow tell barebox 'use the partition with label "rootfs_1" > for the "root" parameter' and barebox should be able to match my label with > the partition UUID and automatically generate the root= value. > > giorgio grepping a bit through the barebox sources I've found that what I need is actually already implemented! I know that at least one of 'rootfs_1' and 'rootfs_2' must contain a valid userland image (a squashfs image); now, in my 'init' I try to 'mount -t squashfs' rootfs_1: if it works I found that barebox defines a global variable '$squashfs0.linux.bootargs' with exactly the content I need (root=PARTUUID=...). I just have to use this var. to define my global linux.bootarg: global linux.bootargs.root=$squashfs0.linux.bootargs giorgio _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
