sysroot: Support /boot on / for syslinux and uboot #215

cgwalters · 2016-03-22T02:08:34Z

People making smaller operating systems, particularly things like
cloud images, don't need to have /boot as a separate partition.

Build on the code that recently landed to detect whether /boot
is a mountpoint at runtime (for read-only purposes) here in order
to influence bootloader config generation.

Basically if /boot is not a partition, prepend /boot to generated
syslinux/uboot config.

NOTE: not tested in a real world scenario for either syslinux or
uboot, but I did extend the test suite to cover this.

https://bugzilla.gnome.org/show_bug.cgi?id=751666

cgwalters · 2016-03-30T17:47:49Z

Or, would it work to just drop the leading /? Hmm...I guess not in general if someone installs extlinux to /boot/extlinux.

cgwalters · 2016-03-31T19:12:13Z

bot, retest this please

cgwalters · 2016-04-02T15:46:42Z

I finally got around to testing this a bit by converting a CentOS Atomic Host image from grub2->extlinux using libguestfs. (That was a fun process and I hit https://bugzilla.redhat.com/show_bug.cgi?id=1099237 again...what was really broken is libguestfs claimed to support turning off 64 bit but didn't actually do it 😭 ).

Anyways, when things booted I immediately noticed /boot is a bind mount, and then I remembered about https://bugzilla.gnome.org/show_bug.cgi?id=756267

So...this leads me to believe that somehow u-boot has been working without this patch. John, does u-boot do something like search in /boot automatically as well?

cgwalters · 2016-04-02T15:50:30Z

To complete the picture here more sanely, since we already detect on bootup whether we're in a single partition approach, maybe ostree-prepare-root could touch /run/ostree/sharedboot, or maybe instead we detect whether /sysroot/boot is the same as /boot?

I think we still need an environment variable for OS builders that are doing cross builds, or alternatively/in addition a command line switch to ostree admin deploy (and that gets passed to the API)?

gatispaeglis · 2016-04-04T15:01:43Z

So...this leads me to believe that somehow u-boot has been working without this patch. John, does u-boot do something like search in /boot automatically as well?

I don't think so. U-boot sources uEnv.txt and then does something like:
load mmc ${bootpart} ${loadaddr} ${kernel_image}

Where kernel_image=/ostree/qt-os-590db09c66551670019a487992f4dae9cb2067e241f7c7fefd6b3d35af55895b/vmlinuz

So to make this work on a single partition system one would need to add the "boot" prefix:
bootdir="/boot".
loaduimage=load mmc ${bootpart} ${loadaddr} ${bootdir}${kernel_image}

I think we still need an environment variable for OS builders that are doing cross builds, or alternatively/in addition a command line switch to ostree admin deploy (and that gets passed to the API)?

Having OSTree to provide a full path is just a convenience in my opinion. Otherwise system builders can take care of this, as partition layout is static and the necessary prefix needs to be configured only once - when bringing up the system.

wmanley · 2016-08-02T21:28:49Z

So...this leads me to believe that somehow u-boot has been working without this patch. John, does u-boot do something like search in /boot automatically as well?

u-boot on the Tegra TK-1 does this at least. Here's a simplified excerpt that I've formatted for clarity:

boot_prefixes=
    /
    /boot/

scan_dev_for_boot=
    echo Scanning ${devtype} ${devnum}...;
    for prefix in ${boot_prefixes};
    do
        run scan_dev_for_extlinux;
    done

scan_dev_for_extlinux=
    if test -e ${devtype} ${devnum}:${bootpart} ${prefix}extlinux/extlinux.conf;
    then
        echo Found ${prefix}extlinux/extlinux.conf;
        run boot_extlinux;
        echo SCRIPT FAILED:
        continuing...;
    fi

boot_extlinux=
    sysboot ${devtype} ${devnum}:${bootpart} any ${scriptaddr} ${prefix}extlinux/extlinux.conf

The full set of u-boot environment looks like this:

# env print
arch=arm
baudrate=115200
board=jetson-tk1
board_name=jetson-tk1
boot_a_script=load ${devtype} ${devnum}:${bootpart} ${scriptaddr} ${prefix}${script}; source ${scriptaddr}
boot_extlinux=sysboot ${devtype} ${devnum}:${bootpart} any ${scriptaddr} ${prefix}extlinux/extlinux.conf
boot_prefixes=/ /boot/
boot_scripts=boot.scr.uimg boot.scr
boot_targets=mmc1 mmc0 usb0 pxe dhcp 
bootcmd=setenv usb_need_init; for target in ${boot_targets}; do run bootcmd_${target}; done
bootcmd_dhcp=run usb_init; if dhcp ${scriptaddr} boot.scr.uimg; then source ${scriptaddr}; fi
bootcmd_mmc0=setenv devnum 0; run mmc_boot
bootcmd_mmc1=setenv devnum 1; run mmc_boot
bootcmd_pxe=run usb_init; dhcp; if pxe get; then pxe boot; fi
bootcmd_usb0=setenv devnum 0; run usb_boot
bootdelay=2
bootpart=1
cpu=armv7
ethact=RTL8169#0
ethaddr=00:04:4b:5a:f1:d3
fdt_addr_r=0x82000000
fdt_high=ffffffff
initrd_high=ffffffff
kernel_addr_r=0x81000000
loadaddr=0x80408000
mmc_boot=if mmc dev ${devnum}; then setenv devtype mmc; run scan_dev_for_boot; fi
pxefile_addr_r=0x90100000
ramdisk_addr_r=0x82100000
scan_dev_for_boot=echo Scanning ${devtype} ${devnum}...; for prefix in ${boot_prefixes}; do run scan_dev_for_extlinux; run scan_dev_for_scripts; done
scan_dev_for_extlinux=if test -e ${devtype} ${devnum}:${bootpart} ${prefix}extlinux/extlinux.conf; then echo Found ${prefix}extlinux/extlinux.conf; run boot_extlinux; echo SCRIPT FAILED: continuing...; fi
scan_dev_for_scripts=for script in ${boot_scripts}; do if test -e ${devtype} ${devnum}:${bootpart} ${prefix}${script}; then echo Found U-Boot script ${prefix}${script}; run boot_a_script; echo SCRIPT FAILED: continuing...; fi; done
scriptaddr=0x90000000
soc=tegra124
stderr=serial
stdin=serial
stdout=serial
usb_boot=run usb_init; if usb dev ${devnum}; then setenv devtype usb; run scan_dev_for_boot; fi
usb_init=if ${usb_need_init}; then setenv usb_need_init false; usb start 0; fi
vendor=nvidia

Environment size: 1997/8188 bytes

copumpkin · 2016-08-15T18:34:10Z

What's left to do? This seems pretty appealing to me. Is it worth trying out (as a comparative "end user") in the current state?

People making smaller operating systems, particularly things like cloud images, don't need to have /boot as a separate partition. Build on the code that recently landed to detect whether /boot is a mountpoint at runtime (for read-only purposes) here in order to influence bootloader config generation. Basically if /boot is not a partition, prepend `/boot` to generated syslinux/uboot config. NOTE: *not* tested in a real world scenario for either syslinux or uboot, but I did extend the test suite to cover this. https://bugzilla.gnome.org/show_bug.cgi?id=751666

cgwalters · 2016-12-09T22:59:17Z

Rebased for testing 🔬

vtolstov · 2016-12-15T21:55:37Z

gentle ping...

vtolstov · 2016-12-20T09:49:43Z

I'm test this pr and don't see that /boot prepended i think this is becasue /boot on / not dedicated partiono , but /boot/efi is the partition. I can delete move all stuff to efi partition but in this case (as i remember) fedora installer complain about that /boot/efi needs to be separate partition.

vtolstov · 2017-01-12T19:48:33Z

@cgwalters gentle ping... as of user that does not have separate /boot =)

cgwalters · 2017-01-18T22:59:53Z

Right, this code basically needs to be aware of /boot/efi on Fedora and probably other systems. This gets into a vague area of system dependency. Simplest is likely a build-time option.

cgwalters · 2017-01-18T23:01:24Z

Sort of related to this...one thing on the back of my mind here is that it'd be safer if we created a container with a new mount namespace, and just mounted read-write there. That way /boot wouldn't be transiently writable by other processes too.

vtolstov · 2017-03-02T20:14:45Z

does it possible to finish and merge this pr ?

cgwalters · 2017-03-03T02:35:04Z

This blocks on redoing the grub2 backend, see #706

rh-atomic-bot · 2017-03-24T22:27:27Z

☔ The latest upstream changes (presumably 455cc5e) made this pull request unmergeable. Please resolve the merge conflicts.

cgwalters · 2018-01-10T14:06:47Z

Obsoleted by #1404

This introduces a new config value "sysroot.boot_path_on_disk": > Tell ostree where the bootloader will be looking for the kernel. This is > the location of `/boot` relative to the root of the boot partition. > > This allows explicitly telling ostree that the boot partition is or is > not separate from the root partition. If `/boot` is on root set this to > `/boot`. If it's on seperate partition this should be set to `/`. > > This must be either an absolute path (starting with `/`) or `auto`. > Defaults to `auto`. > > This setting currently only respected by the u-boot and syslinux > bootloaders. This commit is based on an original by Colin Walters (ostreedev#215), but takes a different tack. ostreedev#215 attempts to determine automatically whether `/boot` is on root or not, but there are always situations where this isn't possible so I'm adding a config option here so the user can make it explicit. Future commits can add the automatic detection in, but this means that we don't need to be completely general with the auto-detection.

cgwalters mentioned this pull request Mar 30, 2016

[merged] Introducing ostree-grub-generator #228

Closed

cgwalters force-pushed the bootloader-no-boot-partition branch from de000be to f870614 Compare March 31, 2016 19:11

cgwalters added the WIP label Apr 19, 2016

cgwalters mentioned this pull request Jul 22, 2016

[merged] ostree-prepare-root as init #403

Closed

4 tasks

cgwalters force-pushed the bootloader-no-boot-partition branch from f870614 to a995ffd Compare December 9, 2016 22:59

This was referenced Jan 9, 2018

Support for booting without initramfs (rebased) #1401

Closed

sysroot: Support /boot on / for syslinux and uboot #1404

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cgwalters closed this Jan 10, 2018

wmanley mentioned this pull request Jul 8, 2020

sysroot: Support customising /boot on root for syslinux and u-boot #2145

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sysroot: Support /boot on / for syslinux and uboot #215

sysroot: Support /boot on / for syslinux and uboot #215

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sysroot: Support /boot on / for syslinux and uboot #215

sysroot: Support /boot on / for syslinux and uboot #215

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cgwalters commented Mar 22, 2016

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