[kubatyszko]

The caveat: You'll be doing a clean install of the same version of IRIX that you already have running. I don't think this will work for different architectures or machine types.
You might ask what is the advantage of that over booting the machine and installing from network or other media ?
Well, you get to continue using your machine while it's installing the OS, no need for single user etc.
No need to use xfsdump|xfsrestore combo. Also, it's useful if you want a clean install that doesn't carry baggage of whatever you have on your current system (which xfsdump/xfsrestore would retain)

Note, the device paths here are from Octane, your system might use different paths, or look at robespierre's response and try the portable paths (which I haven't tested here).

Step one, partition the new drive, standard process:  

Code:

fx , prtvtoc, dvhtool (copy over sash, ide depending on the machine type), mkfs etc.

(In my case, it was disk3)

Code:

mount /dev/dsk/dks0d3s0 onto /x

inst -t /x

Add all the sources you need, at least you're going to need 3 x Overlays , 2 x Foundation, I also recommend apps, complementary apps and nfs.

With this set up you should have very few conflicts, it's ok to ignore.

The "-t /x" ensures that your installation goes onto the new drive

Once inst is done, copy /unix into /x/unix

reboot the machine into PROM

in prom, you can then verify if the new disk is readable: 

Code:

ls dksc(0,3,8)/
^ should work on any machine

ls xio(0)pci(15)scsi(0)disk(3)rdisk(0)partition(8)/
^ specific to octane

boot manually to test the kernel : 

Code:

boot -f disc(0,3,8)/sash
^ should work on any machine
^this will run sash, then you need to run the kernel
OR

boot -f xio(0)pci(15)scsi(0)disk(3)rdisk(0)partition(8)/sash
^ octane specific
^this will run sash, then you need to run the kernel

boot -f dksc(0,3,0)/unix
^ should work on any machine

boot -f xio(0)pci(15)scsi(0)disk(3)rdisk(0)partition(0)/unix
^ octane specific

It will use the "new" kernel, but "old filesystem" on the old disk, that's fine. Boot into IRIX and reboot again into PROM

Now, edit both variables via setenv:

Code:

                                                v
setenv SystemPartition xio(0)pci(15)scsi(0)disk(3)rdisk(0)partition(8)
setenv OSLoadPartition xio(0)pci(15)scsi(0)disk(3)rdisk(0)partition(0)
                                                ^
                                        disk 3 in my case, not disk 0, path specific to Octane

setenv SystemPartition dksc(0,3,8)
setenv OSLoadPartition dksc(0,3,0)
                                                ^
                                        disk 3 in my case, not disk 0, this should work on any machine

Boot irix by typing "auto" and enjoy running IRIX from another drive.
You should now be able to remove all other drives and move the new one to the primary bay,
don't forget to edit both variables in prom back to disk(0)

While you're booting system from disk(3) - note something interesting in IRIX.
Root (/) filesystem is symlinked to /hw/disk/root - which in turn is /hw/dsk/dks03 - something. But note the major/minor number - it's 0,251
If you boot IRIX from disk(0) - the major/minor numbers are the same, 0,251 - so IRIX treats the drives differently than Linux would. In Linux the device node would be respective to the drive, and the major/minor between drive0 and drive3 would be different, regardless of which one is used for root filesystem.

[robespierre]

Those device paths are machine-specific; they will only work on machines whose SCSI controllers are connected to the specific I/O hub chips in that path.

The portable way to choose partitions in the PROM is

Code:

>> setenv SystemPartition dksc(0,3,8)
>> setenv OSLoadPartition dksc(0,3,0)

and when you want to return to the defaults, you can simply unset those variables.

Code:

>> unsetenv SystemPartition
>> unsetenv OSLoadPartition
>> init

There is a typo in your instructions:

boot manually to test the kernel :

Code:

boot -f xio(0)pci(15)scsi(0)disk(3)rdisk(0)partition(8)/unix

That should say boot (no -f) dksc(0,3,0)/unix (it's a 0 not an 8).
The boot command is specified to use the OSLoader (which is normally sash) by default. Sash is able to read files on the XFS partitions, the PROM is not. The -f option is to override the default and choose the loader yourself, which cannot be unix in this scenario, because it is on an XFS partition.

It would also be a better idea to pass initstate=s root=dks0d3s0 swap=dks0d3s1 in the boot command, because otherwise unix could trash your existing disk.

[kubatyszko]

Those device paths are machine-specific; they will only work on machines whose SCSI controllers are connected to the specific I/O hub chips in that path.

The portable way to choose partitions in the PROM is

Code:

>> setenv SystemPartition dksc(0,3,8)
>> setenv OSLoadPartition dksc(0,3,0)

and when you want to return to the defaults, you can simply unset those variables.

Code:

>> unsetenv SystemPartition
>> unsetenv OSLoadPartition
>> init

There is a typo in your instructions:

boot manually to test the kernel :

Code:

boot -f xio(0)pci(15)scsi(0)disk(3)rdisk(0)partition(8)/unix

That should say boot (no -f) dksc(0,3,0)/unix (it's a 0 not an 8).
The boot command is specified to use the OSLoader (which is normally sash) by default. Sash is able to read files on the XFS partitions, the PROM is not. The -f option is to override the default and choose the loader yourself, which cannot be unix in this scenario, because it is on an XFS partition.

It would also be a better idea to pass initstate=s root=dks0d3s0 swap=dks0d3s1 in the boot command, because otherwise unix could trash your existing disk.

Right, I think I didn't copy/paste from my notes the sash part, which I now remember I definitely did.
With having to explicitly load sash and then unix, I think that boot -f is what I did and it worked just fine.