On Sun, 10 Jun 2018 08:55:55 -0400
Haines Brown <haines@???> wrote:

> On Sun, Jun 10, 2018 at 10:05:48AM +0200, Didier Kryn wrote:
> > Le 10/06/2018 à 04:01, Haines Brown a écrit :
> > >On Sat, Jun 09, 2018 at 10:36:46PM +0100, Simon Hobson wrote:
> > >>Haines Brown <haines@???> wrote:
> > >>
> > >>>In the partitioning scheme, sda is HD ST1000DX002-2DV1. It has a
> > >>>primary partition that is bootable and the mount point /.
> > >>You probably want to set this partition to unused (or whatever
> > >>it's
> > > called, it's a looong time since I last did this) so that it
> > > doesn't appear in the mount point table (eventually in fstab of
> > > the new install). I think what you are telling it is that you
> > > want sda1 to mounted as / IN THIS INSTALLATION and that then
> > > clashes with your new / (on sdc) that you're trying to install to.
>
> >     In the partitionner (which is not only a partitionner, but
> > generates the fstab and the filesystems), you should select "dont
> > use the partition" on every partition which is not in sdc. Click on
> > "use partition  as"  and select  "dont use the partition".
>
> Didier, that seems to have done the trick. I apologize for having been
> too hasty. Where the partitioner asks what to use a partition as,
> because the top options were simply file systems, I interpreted it to
> be merely for selecting file system and did not notice the "don't
> use" option at the bottom. When I marked sda partitions not to be
> used, I was able to save the sdc partition table and proceed with the
> installation.
>
> Now that installation of ascii 2.0 on sdc is underway and before going
> further I must figure out how to recover a use of partitions on sda. I
> assume that were I to use the menu to revert to partitioning and
> restore usage of sda partitions I'll just end up with the same
> problem of a competition of sda and sdc for use of /.
>
> When I execute a shell toward the end of installation, can I use it to
> run the command "parted /dev/sda set 1 boot on" both to enable sda1
> and to make it bootable at the same time? Would the command
> "parted /dev/sda set 2 on" simply re-enable the second partition? I
> found the parted manual unclear on this point.
>

I am fairly sure you will need to set up grub2 to do this, try reading
this:

https://unix.stackexchange.com/questions/252936/grub2-boot-to-a-second-another-hard-disk

Or failing that, google for the answer ;-)

Rowland