OK, I futzed around with this for quite some time, and now I finally have the SSD configured the way I want it AND it is booting fast.
I learned a lot along the way... some of which isn't in the GParted manual, I think, but perhaps should be.
The first thing I learned is that I wasn't hallucinating when I recalled that gparted didn't seem to want to allow me to just plain move the extended+logical that contained the Ubuntu linux-swap. If there was note in the manual explaning either (a) that gparted will refuse to move extendeds if they contain anything or (b) the reason for this limitation or (c) how to work around the problem, then I must have just missed all of these things, because I didn't see anything in the manual about any of this.
Fortunately, a bit of googling turn up this, which provided information about both (a) and (c), and provided also wnat amounts to a totally inadequate explanation for (b):
http://askubuntu.com/questions/659797/g … -the-right
So once I read the info/explanation/answer at the link above, even though the proedure described there does seem to be ridiculously "Rube Goldberg", at least I understood what I had to do, i.e. (a) expand the extended, (b) move the contained logical to the right hand end of that, and then finally (c) shrink the extended back down again (moving its start rightwards) so that it would again contain just the logical and would have a lot of free space to the left of it. (Why gparted couldn't be endowed with enough smarts to do these three steps for me in one easy request is beyond me.)
Anyway, I tried to do these thing things and learned about even more possible "gotchas" along the way. In the end, here is the recipie that I followed, which did work, and which did result in a nice fast bootable SSD with my cloned & expanded Ubuntu system on it. (Note that this whole thing seems WAY more complex than it ought to be, given that people may want to do this exact thing very frequently, i.e. migrate an Ubuntu system from one physical volume to a newer bigger physical volume, expanding the root filesystem as they go.
So anyway, here's how I migrated & expanded my "default install" Ubuntu from a 16GB USB3 stick to a 120GB SSB. I post these directions here for the benefit of others who may come here seeking complete instructions for doing this. I believe that the same steps are applicable to _any_ case where it is desired to clone & expand a "default install" Ubuntu from one volume "A" to a bigger one "B". (I stress "default install" because I probably could have avoided a lot of these headaches if I had just asked Ubuntu to use GPT partitions... rather than these funky old MBR ones... back when I did the original Ubuntu install onto the initial USB3 stick.)
If there is a simpler way to do any of this, please let me know.
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1) If the media/device containing the existing Ubuntu system... which we will call "A"... doesn't have gparted installed on it, then download and install that. Also get a recent vintage Clonezilla and put that onto a USB stick.
2) Connect both devices A and B as well as the Clonezilla USB stick. Boot Clonezilla from the USB stick.
3) Use Clonezilla to do a verbatim disk-to-disk copy of the whole A disk to B. Be sure to say "Y" when asked if you want to also clone the boot loader.
4) When finished, poweroff.
5) Remove the Clonezilla USB stick AND disconnect device B.
6) Boot from device A (into Ubuntu).
7) *After* booting is done, connect device B. (If you connect it too soon, things can go haywire while attempting to boot from A.)
8) Run gparted and select device B (/dev/sdb).
9) In gparted, click on (thus highlighting) the Ubuntu EXTENDED partition. Then right click on that, and in the resulting drop down menu, select Move/Resize.
10) Decide where you want your relocated Ubuntu swap partition to end, and then adjust the *SIZE* of the extended partition accordingly. Click apply.
11) After you do this, you will note that both the extended partition and the containing logical partitions now have a little key symbol next to them, because they have both now become "locked". The reason that happened is that the resize of the extended partition (done in step 10 above) had a side-effect of causing the running Ubuntu OS (booted from A) to NOW see that there is a "new" and ADDITIONAL swap partition now available on device B. So the running instance of Ubuntu OS (from A) now greedily decides to start using that (i.e. the B swap partition) ALSO as a swap partition, in addition to the one it is already using on A.
12) You won't be able to move or resize the logical swap partition as long as it is locked, so right click on the key symbol next to it and then, in the resulting drop down menu, click "Swapoff". (Note that this setting for this partition is NOT permanent is any sense, and will go away when... eventually, after completion of all the steps below... you reboot from your fully fixed-up device B.)
13) Select the linux-swap LOGICAL partition on device B by clicking on it to highlight it. Then right click on it and select Move/Resize from the drop down menu.
14) In the resulting pop-up menu, set Free Space Following to zero and then click Apply.
15) Click the green check mark icon in the gparted top bar to apply pending operations and click "OK" to confirm.
16) Find the total number of sectors in the linux-swap LOGICAL partition by right clicking on it and then clicking "information".
17) Drag out your calculator and divide the number of sectors in the LOGICAL swap partition (on B) by 2048. Then add one to that result. The resulting number is the number of mebibytes that you will now shrink the containing EXTENDED swap partition (on B) down to.
18) Right click on the EXTENDED partition and in the drop down menu select Move/Resize.
19) Left lick just to the right of whatever number you see in the SIZE field, and then repeatedly hit the backspace key until all digits of that number are erased.
20) Type in the number you got as the final result of the calculations you did in step 17 above, and then hit enter. (Note that when you do this, the "Space Before" number will be automagically adjusted to a proper value.) Then click "Apply".
21) Click the green check mark icon in the gparted top bar to apply pending operations and click "OK" to confirm.
22) Right click on the root (linux boot) partition and in the drop down menu select "Information". Find the "Total Sectors" number in the resulting pop-up information window and divide that by 2048. This is the CURRENT size (in mebibyte) of the root partition. Write down this number.
23) Right click on the chunk of free/unallocated space that should now immediately follow the root partition. Then, in the resulting drop-down menu, click "Information". Find the "Total Sectors" value and divide it by 2048. Write down the result of that division.
24) Add together the two numbers you wrote down in steps 22 and 23 just above. This is the size (in mebibytes) to which you will now expand the root partition.
25) Right click on the root partition and in the resulting drop down menu select "Move/Resize".
26) Click just to the right of whatever number appears in the SIZE data entry field, and then hit the backspace key until all of the digits of that number have been erased. Then type into the same SIZE data entry field the result you got from step 24 above. Then hit enter. Then click "Apply".
27) Click the green check mark icon in the gparted top bar to apply pending operations and click "OK" to confirm.
28) Shut down / Power Off the system.
29) Remove/disconnect device A.
30) Reboot the system using only device B.
Congratulations, you're done!
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As I said above, if there is a simpler way to clone+expand an existing "default install" ubuntu system, I would appreciate very much being told about that. Otherwise I will continue to assume that yes, it really _is_ necessary to go through all of the above in order to do this one, seemingly simple thing.
(The apparent fact that a lot of the calculations needed to make this all work properly need to be done *manually* is especially disconcerting. I think that gparted could be a bit more helpful in some cases where those results have to be computed.)
P.S. Obviously, the above procedure is substantially different from what I had done before, i.e. first deleting and then recreating from scratch (using gparted) the linux-swap extended & logical partitions in a different location on the SSD. With 20/20 hindsight I can confidently say with certainty that *that* was clearly a Bad Idea. I'm still not at all sure why doing it that way resulted in a system which was at once both (a) still bootable but also (b) REALLY slow. But perhaps that's just one of life's little mysteries that I'll never know the answer to.