How do you manage multiple distros with grub2?

xaos52 · 2012-01-05 15:26:37

I think sometimes you can learn more from one concrete example than from an entire book, so here is how I manage things with grub2.

Following is the output of the 'fdisk -lu' command for /dev/sda ( 80GB HDD )

/dev/sda1   *        2048    39064547    19531250   83  Linux
/dev/sda2        78129150   156301311    39086081    5  Extended
/dev/sda3        39065600    78127103    19530752   83  Linux
/dev/sda5       155258880   156301311      521216   82  Linux swap / Solaris
/dev/sda6        78129152   107423743    14647296   83  Linux
/dev/sda7       107425792   130861055    11717632   83  Linux
/dev/sda8       130863104   155252735    12194816   83  Linux

used as follows:

sda1: my 'main' linux system: #! february upgraded to sid
sda3: #! february upgraded to aptosid
sda5: common swap file
sda6: #! february upgraded to testing
sda7: #! november
sda8: #! november

The differences between similar installs are customizations/installed packages.

I manage the grub2 menu from /dev/sda1.

/sudo:root@crunchie:/media/sda1/etc/grub.d:
total 76
drwxr-xr-x   2 root root  4096 Jan  4 13:34 .
drwxr-xr-x 152 root root 12288 Jan  4 13:39 ..
-rwxr-xr-x   1 root root  6711 Aug  9 02:46 00_header
-rwxr-xr-x   1 root root  5407 Jan 18  2011 05_debian_theme
-rwxr-xr-x   1 root root  5947 Aug  9 02:46 10_linux
-rw-r--r--   1 root root  6344 Aug  9 02:46 20_linux_xen
-rw-r--r--   1 root root  5975 Aug  9 02:46 30_os-prober
-rwxr-xr-x   1 root root  3122 Jan  4 13:34 40_custom
-rwxr-xr-x   1 root root    95 Aug  9 02:46 41_custom
-rwxr-xr-x   1 root root  2155 Dec 23 00:36 60_grub-imageboot
-rw-r--r--   1 root root   483 Aug  9 02:46 README

30_os-prober is not executable.
The rest of the files is standard, except for 40_custom, where I put the grub2 menu items for all partitions, except for /dev/sda1.

40_custom:

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
menuentry "Aptosid, with Linux 2.6.39-3.slh.1-aptosid-686 (on /dev/sda3)" --class gnu-linux --class gnu --class os {
    insmod part_msdos
    insmod ext2
    set root='(hd0,msdos3)'
    search --no-floppy --fs-uuid --set=root 8054743d-4ba9-43c2-94d9-1d94972495f7
    linux /boot/vmlinuz-2.6.39-3.slh.1-aptosid-686 root=UUID=8054743d-4ba9-43c2-94d9-1d94972495f7 ro vga=793 quiet nomodeset
    initrd /boot/initrd.img-2.6.39-3.slh.1-aptosid-686
}
menuentry "Crunchbang 20111125 upgraded to testing, with Linux 3.1.0-1-686-pae (on /dev/sda6)" --class gnu-linux --class gnu --class os {
    insmod part_msdos
    insmod ext2
    set root='(hd0,msdos6)'
    search --no-floppy --fs-uuid --set=root 74a0c02a-40a8-4345-b051-a6fe7b449cbb
    linux /boot/vmlinuz-3.1.0-1-686-pae root=UUID=74a0c02a-40a8-4345-b051-a6fe7b449cbb ro quiet nomodeset vga=793
    initrd /boot/initrd.img-3.1.0-1-686-pae
}
menuentry "Crunchbang 20111125 upgraded to testing, with Linux 2.6.39-bpo.2-686-pae (on /dev/sda6)" --class gnu-linux --class gnu --class os {
    insmod part_msdos
    insmod ext2
    set root='(hd0,msdos6)'
    search --no-floppy --fs-uuid --set=root 74a0c02a-40a8-4345-b051-a6fe7b449cbb
    linux /boot/vmlinuz-2.6.39-bpo.2-686-pae root=UUID=74a0c02a-40a8-4345-b051-a6fe7b449cbb ro quiet nomodeset vga=793
    initrd /boot/initrd.img-2.6.39-bpo.2-686-pae
}
menuentry 'CrunchBang 20111125-fresh, with Linux 2.6.39-bpo.2-686 (on /dev/sda7)' --class debian --class gnu-linux --class gnu --class os {
    insmod part_msdos
    insmod ext2
    set root='(hd0,msdos7)'
    search --no-floppy --fs-uuid --set 2987b1e7-7b8b-47f3-9f0e-093a179f71ff
    linux    /boot/vmlinuz-2.6.39-bpo.2-686 root=UUID=2987b1e7-7b8b-47f3-9f0e-093a179f71ff ro  quiet splash nomodeset vga=793
    initrd    /boot/initrd.img-2.6.39-bpo.2-686
}
menuentry 'CrunchBang 20111125-fresh, with Linux 2.6.39-bpo.2-486 (on /dev/sda7)' --class debian --class gnu-linux --class gnu --class os {
    insmod part_msdos
    insmod ext2
    set root='(hd0,msdos7)'
    search --no-floppy --fs-uuid --set 2987b1e7-7b8b-47f3-9f0e-093a179f71ff
    linux    /boot/vmlinuz-2.6.39-bpo.2-486 root=UUID=2987b1e7-7b8b-47f3-9f0e-093a179f71ff ro  quiet splash nomodeset vga=793
    initrd    /boot/initrd.img-2.6.39-bpo.2-486
}
menuentry 'CrunchBang 20111125-fresh, with Linux 2.6.39-bpo.2-486 (on /dev/sda8)' --class debian --class gnu-linux --class gnu --class os {
    insmod part_msdos
    insmod ext2
    set root='(hd0,msdos8)'
    search --no-floppy --fs-uuid --set 39de84dd-b68a-43e2-99ed-4b25abcf409e
    linux    /boot/vmlinuz-2.6.39-bpo.2-486 root=UUID=39de84dd-b68a-43e2-99ed-4b25abcf409e ro  quiet splash nomodeset vga=793
    initrd    /boot/initrd.img-2.6.39-bpo.2-486
}

• How do I install a new distro?

Lets say I want to install a fresh #! on /dev/sda8 (overwriting what is currently there)
I install from CD-ROM (my old laptop does not support booting from USB).
I always perform a non-graphic, custom install, only touching data on sda8 and the swap file on sda5 ,which
- overwrites the sda8 data
- creates a new filesystem on sda8
- installs / on sda8 -> all installs have their own root directory, no separate /home partitions
- at the end you are asked where to install grub2:
now the #! install allows you to go on, leaving the device where grub has to come blank.
- install finishes and wants you to reboot.
- when you reboot, you will be presented with the old grub menu, because the grub on the MBR is not changed by the new install.
- to be able to boot into your new system, boot into the main system first (sda1)
find out what the kernel-name and initrd-name of your newly installed system are:

sudo geany /etc/grub.d/40_custom

remove the entry/entries for sda8

    sudo mount /dev/sda8 /media/sda8
    sudo geany /media/sda8/boot/grub/grub.cfg

copy the entries for sda8 to the clipboard
paste into the geany window containing 40_custom
save 40_custom

    sudo update-grub -u -k all

reboot your system
you should have a grub menu that includes the new distro on sda8
select that entry
enjoy your fresh install.

Remark:
If you are installing a linux distro that does not let you skip the grub2 install, then:
let it install to the MBR
As a new grub2 is being installed to the MBR, the autoprobe will be active
When you reboot you will have a new grub2 menu, with everyting it found and your new distro in first place.
Do not boot into the new system, select sda1 (your main system)
in your main system:

            1. sudo grub-install /dev/sda

this will re-install grub in the MBR, so that it points again to your 'master' distro, not to the new one

            2. sudo update-grub

this will update the grub menu, and include an entry for the new install.
Reboot
You are presented with your old grub menu, and it allows you to boot into the new one.

I consider this as being worth helping out the crunchbang community for a whole week.

Feedback is always welcome. Good and bad.

If it was of some help to you please mention it in this thread.

Last edited by xaos52 (2012-01-06 14:23:53)

2ManyDogs · 2012-01-06 12:57:57

Very helpful. Thanks. I've bookmarked this thread and will return to it as I configure my test machine.

rhowaldt · 2012-01-06 16:03:32

looks good xaos! i'm sure this will prove useful to me in the future.
just a few pointers, stuff that would give me troubles when i'd read this as a complete noob (instead of the advanced noob i am now.. and some stuff i still don't know how to do smile ) :

1. one of the problems i faced when first building a dual-boot is how partitions work. you gloss over your 'Extended' partition, which is the key to having more than 2 (from the top of my head, or was it more?) partitions on the same disk. now i don't expect you to explain that stuff but maybe you could at least devote a small line to it, and have a link to a page that explains this stuff in more detail?
2. what happened to sda4? just wondering...
3. this:

find out what the kernel-name and initrd-name of your newly installed system are:

how do i do that? consider including the actual command you need to type to find out this info. this is where your very clear and precise how-to suddenly becomes blurry.

el_koraco · 2012-01-06 23:21:37

This is exactly the right way to do it, as expected, since it's coming from you. I wish all those guys plugging their ludicrous setups with grub1 on a separate and belonging to no OS /boot partition and similar would come here and take a look.

Last edited by el_koraco (2012-01-06 23:21:56)

AnInkedSoul · 2012-01-07 01:11:25

What I have been doing with grub2 is similar. At least I think it is, you confused me a bit with the 40_custom file.

I pick one partition and anytime I do an install on that partition I let it install grub to the mbr. That is the only time I install grub at all is when I do an install on that one partition. When I install to any other partition I do not install grub at all. I then boot into the one partition that has grub and run update-grub.

If an install does install grub then I boot into my main partition and reinstall grub and run update-grub. Then I boot into the misbehaving system and uninstall/purge grub completely.

Doing so seems to keep everything sane and stops the duplicated entry craziness that can occur.

Last edited by AnInkedSoul (2012-01-07 01:12:02)

xaos52 · 2012-01-07 11:07:29

@Rhowald: Thanks for your input.
In fact, I did not mean to publish it yet. It is a draft version really that I posted by accident. smile
When I get to cleaning it up I will try to take your suggestions to heart.

xaos52 · 2012-01-07 11:13:17

@AninkedInSoul:
Using 40_custom like I do allows you to heavily edit the labels for your partitions, and keeps those labels unchanged when you run update-grub. Using os-prober on the other hand destroys your custom edits.

xaos52 · 2012-01-07 11:24:50

Thanks, el_k.

Thorny · 2012-01-07 15:06:02

xaos52,
If you take advantage of the symlinks that are created for vmlinuz and initrd.img that are created when a kernel is upgraded for each of your distros and use those in your custom menu (rather than the long version that includes the version number) then you don't have to worry about the step rowaldt is asking about. Your menu doesn't need to be amended with new kernel version numbers after an upgrade of any of your multi distros because the symlinks are created automagically with the kernel upgrade.

I know since it is you doing this I don't need to spell it out any more than that. Just remember that those symlinks are in the root of each filesystem not in /boot so your menu will have to be set that way.

AnInkedSoul · 2012-01-07 16:54:21

xaos52 wrote:

@AninkedInSoul:
Using 40_custom like I do allows you to heavily edit the labels for your partitions, and keeps those labels unchanged when you run update-grub. Using os-prober on the other hand destroys your custom edits.

I see! Good info. I guess I have gotten lazy anymore as os-prober is fine and dandy as long as I do not let it run for every install and start listing all my installs multiple times. Aggravating!

xaos52 · 2012-01-07 16:58:21

Thank you, Thorny.
I had tried this with manually created symlinks in /boot, but it did not work: grub2 immediately returned to the menu. This was on my todo-list.
I will add this to the howto when I get to update it.

Last edited by xaos52 (2012-01-07 17:00:18)

Thorny · 2012-01-07 17:30:51

xaos52 wrote:

I will add this to the howto when I get to update it.

Using those symlinks is oldschool, something we used to use with grub-legacy too, I imagine that's why their creation was included in the kernel install in the first place. I am not sure that all current distros available include that automagic but all the ones I have tried do and it could be done manually if required but that wouldn't be much different from your first draft.

You expend a lot of energy around here and it is very positive, don't try to do so much that you burn out, this forum would be much less effective without the core of knowledgeable and experienced helpers.

xaos52 · 2012-01-07 17:37:36

OK. Thanks for your concern, Thorny.
I am a retired sysadmin. I have nothing else to do, and I am enjoying it. smile

Thorny · 2012-01-08 10:59:56

xaos52 wrote:

... and I am enjoying it.

That is what matters!

CBizgreat! · 2012-01-14 14:54:29

Thanks for the how to xaos52,

Is bkmarked in case ... Am still too lazy to break away from legacy atm. Adding summin that's kind of related, as you ( others) might like the info. Your PC doesn't support boot from bios ( neither does mine come to think of it and am soooo not going to mess w upgrading bios.) Anyway ... might check out PLop. I've never bothered with it. But looked interesting for folks who want to boot from usb but have bios limitations.

Last edited by CBizgreat! (2012-01-14 14:56:40)

mikhou · 2012-02-14 05:32:57

Just writing in to say thanks for posting this thread. I recently created a small partition for testing new distros, and this was perfect for getting grub2 to act nice with all of my OS's.

mikhou

xaos52 · 2012-02-14 09:04:30

Thanks for the feedback

CrunchBang Linux

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#1 2012-01-05 15:26:37

How do you manage multiple distros with grub2?

#2 2012-01-06 12:57:57

Re: How do you manage multiple distros with grub2?

#3 2012-01-06 16:03:32

Re: How do you manage multiple distros with grub2?

#4 2012-01-06 23:21:37

Re: How do you manage multiple distros with grub2?

#5 2012-01-07 01:11:25

Re: How do you manage multiple distros with grub2?

#6 2012-01-07 11:07:29

Re: How do you manage multiple distros with grub2?

#7 2012-01-07 11:13:17

Re: How do you manage multiple distros with grub2?

#8 2012-01-07 11:24:50

Re: How do you manage multiple distros with grub2?

#9 2012-01-07 15:06:02

Re: How do you manage multiple distros with grub2?

#10 2012-01-07 16:54:21

Re: How do you manage multiple distros with grub2?

#11 2012-01-07 16:58:21

Re: How do you manage multiple distros with grub2?

#12 2012-01-07 17:30:51

Re: How do you manage multiple distros with grub2?

#13 2012-01-07 17:37:36

Re: How do you manage multiple distros with grub2?

#14 2012-01-08 10:59:56

Re: How do you manage multiple distros with grub2?

#15 2012-01-14 14:54:29

Re: How do you manage multiple distros with grub2?

#16 2012-02-14 05:32:57

Re: How do you manage multiple distros with grub2?

#17 2012-02-14 09:04:30

Re: How do you manage multiple distros with grub2?

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