[Nottingham] Dual booting (rearranging existing partitions!)

[Martin]

Nigel,

Good to see you online. Hope you are all keeping well over there?


On 02/11/2020 20:22, NIGEL Black via Nottingham wrote:
[---]
> I've considered removing the initial system in order to do so.  It
> raises the question of whether fiddling with sda1 and sda2 (see
> attachment) to make room for the new system automatically renumbers the
> remaining partitions and whether that has any operational consequences.

As always... That 'depends' ;-)

I've never used the graphical GParted for anything other than a 'bare
metal' new install. So I can't comment upon the intricacies of exactly
what GParted will do. Best is to give it a try and to look very
carefully /before/ committing to write the partition table. (It allows a
quit without saving/writing any changes if you don't like the looks of
the results.)

Whether the physical partition numbers matter depends upon how your boot
loader and OS finds the partitions.

For myself, I always avoid using absolute partition numbering as far as
is possible.

I always use labels or UUIDs for identifying the partitions and the file
systems. That way, there are no problems if the disk order changes or
even if partitions are rearranged.

Aside: Where appropriate, I do not use partitions or MBRs at all! Using
such as btrfs, an entire physical disk can be used as the filesystem
(and then use subvolumes). However, you still need a boot disk/device
somewhere...

The only 'fixed' aspect for old-style BIOSes is to tell the BIOS where
the boot record is.


Commenting for your example:

*Firstly* *Make a full backup*

Assume that you may well lose everything on that disk.

> I would like to replace the existing sda1 and sda2 with three partitions
> for the new system, swap and home; delete sda4 and resize sda7 into the
> empty space. (ie keep and expand the extended sda3).
> 
> What are the pitfalls? Should any partition be left untouched?

Just to state the complete obvious:

That will eradicate the Windows system and leave you bootless until you
install a new system.


So...

Yes, you can delete partitions sda1, sda2, sda4.

Create new partitions sda1 and sda2 to fill the space up to the
beginning of sda3. Note that sda3 is an 'extended partition' that
contains sda5, sda6 and sda7. Keep sda3, sda5, sda6, sda7 in place.

GParted /should/ be intelligent enough to allow you to extend sda7 to
fill the remaining space on the disk (sda3 should also automatically
adjust for that, or you might need to increase the size of sda3 first).

You can reuse sda6, unchanged, for your swap space.

Leaving sda5 and sda7 untouched means that data will safely remain there.

You may well need to manually select/initiate a resize for the ext4 for
sda7. That can be another maillist posting if you wish.

When installing your new linux system, ensure that you select to use a
custom install so that you can select to use the partitions as you have
already set up with GParted.

I'd suggest a generous 512MBytes for your boot partition (sda1). With
mainstream distros, I've seen 128MBytes and 256MBytes boots fill up too
easily!


> How are the virtual group meetings working out?  I look forward to
> 'real' sessions again.

Hopefully, we're all looking forward to clean freedom again!

Yes, the meets work well and are going steady. Jitsi works well. And the
group meets work well enough even with the constrains of the
videoconferencing format.


However:

Great shame we miss the chance for hands-on demos and being Human
sociable. However, until we get a vaccine against COVID-19, we're stuck
with exploring 'high tech' socialising.

Shame we can't educate the rest of the unclean of the UK to be more
conscientious so that we all could enjoy having already eradicated the
Coronavirus-SARS2 silliness!


Good luck and good patience for your new install!

Hope to see you on the next video meet?

Cheers,
Martin