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Re: Debian 8 and Debian 9 Dual Boot

On 11/16/2017 02:27 PM, Joe wrote:
On Thu, 16 Nov 2017 13:34:52 -0500
Dan Norton <dnorton@mindspring.com> wrote:

On 11/13/2017 09:52 PM, Felix Miata wrote:
Dan Norton composed on 2017-11-13 21:38 (UTC-0500):
How do you set up LVM so that install does not clobber one of the
siblings? During installation, for partitioning, do you pick
"Manual" or "Guided -*" ?
I don't think I've ever used Debian's, or any Debian derivative's,
"guided". I can't remember the last time I didn't pick manual,
after *fully* preparing in advance to my specifications.

Manual will list what partitions and volumes exist, so if you've
fully prepared logical volumes in advance, all that should need to
be done within manual is select mount points and mount options for
those you wish used. If volumes exist but are not formatted, then
formatting would be a third selection using manual.
A better description of what I want is "multiboot", instead of "dual
boot" in this thread. I can see having up to 4 systems installed, all
Debians, on one disk drive. There is an item in [1] which I see that

    6. Disable LVM support

which is puzzling. Can multiboot be set up within LVM on one disk
drive? Or, is it necessary to disable  LVM, define multiple logical
partitions with fdisk or parted for example, install in these
partitions, and then set up LVM separately on each system?
I see the date of the page is 2015, but to be honest, a lot of this
page is completely obsolete, even more so if you're not using DOS, OS/2
or early Windows. I would not even swear that item 6, LVM, even refers
to the Linux system. There's certainly no problem about mixing multiple
booting with lvm.

Glad to hear it!

A volume group would normally be declared within a single old-style IBM
partition, but doesn't have to be. Think of multiple hard drives, each
containing multiple old-style partitions, then think of multiple lvm
volume groups, each with multiple volumes, roughly overlaid on the
drives and partitions but not physically matching them. A volume group
can consist of multiple complete partitions on different drives, and
the volumes it contains need not bear any relationship to the
underlying partitions.

Multiple OSes will still use one overall bootloader, which may or may
not redirect to other bootloaders. It is common, therefore, to use a
single physical partition for /boot, common to all *nix OSes, but by no
means necessary. /boot can be an LVM volume if you wish, but a booting
problem is slightly easier to deal with if the kernel and grub stuff is
in a standard partition, you don't need to worry about looking up the
lvm commands in addition to the grub set.

My workstation, for example, has a 1GB primary partition for /boot, and
the rest of the drive is a second primary partition which maps exactly
to a volume group. The volume group is then divided into volumes, which
mostly act like old-style partitions, at least as far as mounting goes.
You can have a lot of them.
Apparently there are many ways to do multiboot in LVM. Is it practical to, on one fairly large (1TB) disk, [I can hear the snickers when someone reads this when 1TB is puny in a year or two] do the following:

1. Enlarge the volume group to span the entire disk (it's currently 40G).
2. Define a number of additional logical volumes, say 3.
3. Install stable in one of the lv's and have install treat it like a standard *partition* (logical) and have within it separate root, swap, /var, /tmp, and /home?

 - Dan

I have two drives set up the same, as I migrated from one to a newer
one. After adjustment, the grub installation of the new drive handles
the boot, and the kernel used by the old system lives in the /boot
partition of the old drive. All of this could have been integrated into
one volume group, but it's two because that's how the system evolved. I
could pull the old drive, which I hardly ever touch now, plonk it into
another PC and boot it with minimal fiddling about.

So you have a common grub, basically from the latest installation
unless you tell the installer otherwise, and before the installation is
finished it should have detected any other bootable OSes anywhere in
the hardware. You've been advised not to share other partitions, even
/home, but several /homes can live in differently-named lvm volumes in
the same volume group. Or not, by your preference. You can, for the
most part, treat volumes as partitions, and not worry about whether
they are primary or logical.

You should probably track down a few tutorials on multiboot and lvm,
read through them to get a feel for what needs doing. It's always
difficult reading a manual for something and working out from that what
steps you need to take to do something. Things like UEFI boot and disc
encryption complicate things, so probably best to avoid them on your
first attempt(s) if the hardware allows. If you're starting with a bare
drive and your BIOS allows old-style IBM partitioning, that's the way
to go to get the hang of this.

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