REVISITING - More BTRFS fun Multibooting to subvolumes - FIXING GRUB

[steve7233]

Slight boot problem. 'You need to boot the kernel first.' After that it went to the boot menu. I selected advanced options and the top kernel. Kubuntu booted properly after that.
Snippit from grub.cfg

menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-27a9a212-d177-4665-b6bc-bf304e8c1f3e' {
	recordfail
	load_video
	gfxmode $linux_gfx_mode
	insmod gzio
	if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
	insmod part_msdos
	insmod btrfs
	set root='hd0,msdos5'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos5 --hint-efi=hd0,msdos5 --hint-baremetal=ahci0,msdos5  27a9a212-d177-4665-b6bc-bf304e8c1f3e
	else
	  search --no-floppy --fs-uuid --set=root 27a9a212-d177-4665-b6bc-bf304e8c1f3e
	fi
       linux	/@Kubuntu1704/boot/vmlinuz-4.10.0-35-generic root=UUID=27a9a212-d177-4665-b6bc-bf304e8c1f3e ro rootflags=subvol=@Kubuntu1704  quiet splash $vt_handoff
	initrd	/@Kubuntu1704/boot/initrd.img-4.10.0-35-generic
}

It doesn't seem to be loading the new volumes. Why not?

[oshunluvr]

I'm not clear on what you mean by "It doesn't seem to be loading the new volumes. Why not?" because you don't say why you believe that to be the case. Assuming the above is from your grub.cfg, it looks normal to me.

What's the output of "mount" once you've booted?
Did you edit @Kubuntu1704/etc/fstab to show the new subvolume names?

If you managed to get it to boot and you've edited the correct fstab and the mounts are correct - then run "sudo update-grub" and it will "fix" grub.cfg for you and you should be good to go.

[steve7233]

I'm not clear on what you mean by "It doesn't seem to be loading the new volumes. Why not?" because you don't say why you believe that to be the case. Assuming the above is from your grub.cfg, it looks normal to me.

What's the output of "mount" once you've booted?
Did you edit @Kubuntu1704/etc/fstab to show the new subvolume names?

If you managed to get it to boot and you've edited the correct fstab and the mounts are correct - then run "sudo update-grub" and it will "fix" grub.cfg for you and you should be good to go.

steve7233@steve7233-HP-dv6-US:~$ mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
udev on /dev type devtmpfs (rw,nosuid,relatime,size=1964336k,nr_inodes=491084,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,noexec,relatime,size=397444k,mode=755)
/dev/sda5 on / type btrfs (rw,relatime,space_cache,subvolid=257,subvol=/@)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=30,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=13020)
mqueue on /dev/mqueue type mqueue (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
/dev/sda5 on /home type btrfs (rw,relatime,space_cache,subvolid=258,subvol=/@home)
tmpfs on /run/user/119 type tmpfs (rw,nosuid,nodev,relatime,size=397440k,mode=700,uid=119,gid=127)
tmpfs on /run/user/1000 type tmpfs (rw,nosuid,nodev,relatime,size=397440k,mode=700,uid=1000,gid=1000)

[steve7233]

Yes I edited fstab. They changes appear not have taken effect. I specifically selected save from the file menu. Is there a bug in Kate or something? When I edited grub I clicked on the close button in the title bar and selected save. Maybe the menu is bugged, but closing via the title bar button and selecting save works.

[vinnywright]

from your "mount" output it dose not appear that you did rename the subvolumes ,,,,if you had their would be no @ to mount .

your grub config looks good for the FIRST boot ,,,,,,but since you booted from the "advanced options " at the boot screen you were in a different part of the grub menu than that that you edited.

the grub should be good,,,,,you got the "You need to boot the kernel first." because you did not rename the subvolumes and grub was looking for the renamed names (@Kubuntu1704) and could not find it .

make sure the /etc/fstab is edited as well ,,,,,,,I do not thik it is @now ,,,,,,,or you would not have been able to boot on the advanced options either as the system would be trying to mount @Kubuntu1704 ,,,and their is none .

VINNY

[steve7233]

@Vinney apparently you missed the part where I said that kate failed to save the changes even thought kate said it was saving them.

[vinnywright]

@Vinney apparently you missed the part where I said that kate failed to save the changes even thought kate said it was saving them.

no I did not miss it ,,,,I was just telling how I new from your info what was what .

did you do the edits from a live system (the installation media) or the running system ?

VINNY

[steve7233]

Ahh, I Forgot the last part in the name. I'll fix that and reboot. I was watchingSeason 3 of Dark Matter on Netflix on the big monitor and must have got side tracked by the action.
I can see the head lines now: "Dark Matter causes Kubuntu 17.04 boot error!"

[steve7233]

grub.cfg had a couple of typos that everyone kept overlooking. Uppercase K when lower was used in the sub volume name.

[steve7233]

Finally!!!

steve7233@steve7233-HP-dv6-US:~$ mount |grep btrfs
/dev/sda5 on / type btrfs (rw,relatime,space_cache,subvolid=277,subvol=/@kubuntu1704)
/dev/sda5 on /home type btrfs (rw,relatime,space_cache,subvolid=278,subvol=/@kubuntu1704_home)
steve7233@steve7233-HP-dv6-US:~$

I updated grub and rebooted. All is well! By the way I noticed a reboot bug during the last reboot. It seemed to hang about the end of the process. I had to power reset then startx a few times then it corrected itself -No Kwin -. I rebooted again then everything worked. I waited until I was sure it booted properly then run grub-update and rebooted. Now for a break.

[vinnywright]

grub.cfg had a couple of typos that everyone kept overlooking. Uppercase K when lower was used in the sub volume name.

I do not recall ever seeing your subvolume names been shown to us/everyone in any konsole output .

glad you got it sorted however ,,,welcome to the wonderful world of btrfs

and all the headaches yet to come ,,,,,,,,

hears one for you now ,,,,,a headache that is .

for your next install ,,,,do it without grub .

you can use something like this placed in the current install that controls grub now , in /etc/grub.d/40_custom to boot it.

menuentry 'Neon-lts' {
insmod btrfs
set root='(hd0,msdos1)'
linux /@/vmlinuz root=UUID=ff5d66d4-35b6-4c9c-a64e-8dfbe2aa1e31 rootflags=subvol=@ ro quiet splash
initrd /@/initrd.img
}

of course the (hd0,msdos1) would need to be changed if you are using a GPT partition table , and the UUID would need to be the UUID of your btrfs partition but their is the concept for booting an install without it's own grub install .

aspirin anyone

VINNY

[GreyGeek]

Congrats steve72233 !!!
Welcome to the Btrfs club!




Sent from my iPhone using Tapatalk

[steve7233]

I do not recall ever seeing your subvolume names been shown to us/everyone in any konsole output .

glad you got it sorted however ,,,welcome to the wonderful world of btrfs

and all the headaches yet to come ,,,,,,,,

hears one for you now ,,,,,a headache that is .

for your next install ,,,,do it without grub .

you can use something like this placed in the current install that controls grub now , in /etc/grub.d/40_custom to boot it.

menuentry 'Neon-lts' {
insmod btrfs
set root='(hd0,msdos1)'
linux /@/vmlinuz root=UUID=ff5d66d4-35b6-4c9c-a64e-8dfbe2aa1e31 rootflags=subvol=@ ro quiet splash
initrd /@/initrd.img
}

of course the (hd0,msdos1) would need to be changed if you are using a GPT partition table , and the UUID would need to be the UUID of your btrfs partition but their is the concept for booting an install without it's own grub install .

aspirin anyone

VINNY

Couldn't I just install the other distro without grub then boot into Kubuntu17.04 then run grub-update?

[oshunluvr]

Couldn't I just install the other distro without grub then boot into Kubuntu17.04 then run grub-update?

Go back and read the original article: grub, or more correctly, os-prober, will not find other installs because it can't read inside unmounted subvolumes. That was basically the reason for this entire thread.

Short version: Install a new distro, then edit the 40_custom file as I explained. Then, after updating grub, you will be able to select either install from grub.

You can test/practice this using your current setup. Edit your 40_custom file in your current install and add your original subvolume "@" . Something like this:

menuentry 'Original 17.04 install' { 
   insmod part_gpt 
   insmod btrfs 
   search --no-floppy --fs-uuid --set=root [COLOR=#333333]27a9a212-d177-4665-b6bc-bf304e8c1f3e[/COLOR] 
   configfile /@/boot/grub/grub.cfg 
}

[steve7233]

Where is this 40_custom file as I can not find it?