Focal Testing of Kubuntu 20.04 LTS

[jlittle]

That problem in the screen shot affected the *buntu isos back at the end of October. It was an error in some casper scripts. It's been fixed for a while now; I tried to track down when it was fixed, because I thought I reported it somewhere, but I can't find it now.

[GreyGeek]

GG. might this be a grub vs. btrfs issue? .....
I'm wondering if putting the ISO in the root of @ might allow it to boot?

Interesting! I'll try that and see what happens.
Thanks!

[oshunluvr]

That's pretty much what jlittle was talking about when he referred to grub incantations. Following his lead I found an Ubuntu web page discussing how to do that, which I linked above. I saved the focal iso to /mnt/iso and I then modified an example entry for 40_custom under /etc/grub.d as follows:

menuentry "focal-desktop-amd64 iso - live-only" {
   set isofile="/@/mnt/iso/focal-desktop-amd64.iso"
   loopback loop (hd0,1)$isofile
   linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile noprompt noeject
   initrd (loop)/casper/initrd
}


menuentry "focal-desktop-amd64 iso - persistent" {
   set isofile="/@/mnt/iso/focal-desktop-amd64.iso"
   loopback loop (hd0,1)$isofile
   linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile persistent noprompt noeject
   initrd (loop)/casper/initrd
}

Then I ran "sudo update-grub".

When I tried to fire the "live-only" menu entry it gave me:
[ATTACH=CONFIG]8354[/ATTACH]

When I added "/@/dev/" to the loop reference, "/@/dev/loop", it reported that it couldn't find the kernel.
I can't connect "/@" to initramfs in the menuentry.
I'm at a catch-22.

GG. might this be a grub vs. btrfs issue? Not sure, but when I boot to ISOs from my grub which lives in it's own subvolume, my stanzas look like:

menuentry 'Kubuntu 18.04 ISO' --class iso {
set isofile="/@grub/kubuntu-18.04-desktop-amd64.iso"
loopback loop (hd0,3)$isofile
linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile noprompt noeject
initrd (loop)/casper/initrd.lz
}

Almost exactly the same. I'm wondering if putting the ISO in the root of @ might allow it to boot?

[Radcliff]

Ryzen 2700U

Pretty nice testing pattern. Thanks for sharing!

env DRI_PRIME=1 glmark2 
=======================================================
 glmark2 2014.03+git20150611.fa71af2d
=======================================================
 OpenGL Information
 GL_VENDOR:     X.Org
 GL_RENDERER:   AMD RAVEN (DRM 3.35.0, 5.4.1-050401-generic, LLVM 9.0.0)
 GL_VERSION:    4.5 (Compatibility Profile) Mesa 19.2.4
=======================================================
[build] use-vbo=false: FPS: 3825 FrameTime: 0.261 ms
[build] use-vbo=true: FPS: 4451 FrameTime: 0.225 ms
[texture] texture-filter=nearest: FPS: 3706 FrameTime: 0.270 ms
[texture] texture-filter=linear: FPS: 3716 FrameTime: 0.269 ms
[texture] texture-filter=mipmap: FPS: 3428 FrameTime: 0.292 ms
[shading] shading=gouraud: FPS: 3289 FrameTime: 0.304 ms
[shading] shading=blinn-phong-inf: FPS: 3143 FrameTime: 0.318 ms
[shading] shading=phong: FPS: 3147 FrameTime: 0.318 ms
[shading] shading=cel: FPS: 2917 FrameTime: 0.343 ms
[bump] bump-render=high-poly: FPS: 2273 FrameTime: 0.440 ms
[bump] bump-render=normals: FPS: 4455 FrameTime: 0.224 ms
[bump] bump-render=height: FPS: 4653 FrameTime: 0.215 ms
[effect2d] kernel=0,1,0;1,-4,1;0,1,0;: FPS: 2948 FrameTime: 0.339 ms
[effect2d] kernel=1,1,1,1,1;1,1,1,1,1;1,1,1,1,1;: FPS: 2175 FrameTime: 0.460 ms
[pulsar] light=false:quads=5:texture=false: FPS: 3634 FrameTime: 0.275 ms
[desktop] blur-radius=5:effect=blur:passes=1:separable=true:windows=4: FPS: 1714 FrameTime: 0.583 ms
[desktop] effect=shadow:windows=4: FPS: 2433 FrameTime: 0.411 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 855 FrameTime: 1.170 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=subdata: FPS: 1146 FrameTime: 0.873 ms
[buffer] columns=200:interleave=true:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 808 FrameTime: 1.238 ms
[ideas] speed=duration: FPS: 2380 FrameTime: 0.420 ms
[jellyfish] <default>: FPS: 2156 FrameTime: 0.464 ms
[terrain] <default>: FPS: 217 FrameTime: 4.608 ms
[shadow] <default>: FPS: 2497 FrameTime: 0.400 ms
[refract] <default>: FPS: 322 FrameTime: 3.106 ms
[conditionals] fragment-steps=0:vertex-steps=0: FPS: 3479 FrameTime: 0.287 ms
[conditionals] fragment-steps=5:vertex-steps=0: FPS: 3362 FrameTime: 0.297 ms
[conditionals] fragment-steps=0:vertex-steps=5: FPS: 3498 FrameTime: 0.286 ms
[function] fragment-complexity=low:fragment-steps=5: FPS: 3299 FrameTime: 0.303 ms
[function] fragment-complexity=medium:fragment-steps=5: FPS: 3340 FrameTime: 0.299 ms
[loop] fragment-loop=false:fragment-steps=5:vertex-steps=5: FPS: 3356 FrameTime: 0.298 ms
[loop] fragment-steps=5:fragment-uniform=false:vertex-steps=5: FPS: 3298 FrameTime: 0.303 ms
[loop] fragment-steps=5:fragment-uniform=true:vertex-steps=5: FPS: 3293 FrameTime: 0.304 ms
=======================================================
                               glmark2 Score: 2824

We also adopt Focal as our production machine, but we switch occasionally to TW to see the differences. KDE 5.17.4 is in the pre-release channel since at least yesterday.

Kernel 5.5 is in the oven, should be ready by Sunday night.

lsb_release -a && uname -r
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu Focal Fossa (development branch)
Release:        20.04
Codename:       focal
5.4.1-050401-generic

mokutil  --sb-state
SecureBoot enabled
SecureBoot validation is disabled in shim

inxi -C
CPU:       Topology: Quad Core model: AMD Ryzen 7 2700U with Radeon Vega Mobile Gfx bits: 64 type: MT MCP L2 cache: 2048 KiB 
         Speed: 1368 MHz min/max: 1600/2200 MHz Core speeds (MHz): 1: 1368 2: 1367 3: 1367 4: 1368 5: 1435 6: 1590 7: 1368 
         8: 1367

[NoWorries]

It is now 5 months to the release of Focal.

So far my system has not missed a beat and I use it as my production system. I do not hesitate to use it in meetings and I have used LibreOffice for projection and done many video editing sessions with Kdenlive.

As I use the Pre-release updates with additional repositories for the latest kernel and plasma, I get:

KDE Plasma Version	5.17.3
KDE Frameworks Version	5.64.0
QT Version	5.12.5
Kernel Version	5.4.0-6-generic

As you can see I am very happy with the progress being made and I also have a fallback capability to an earlier version of Kubuntu if Focal lets me down - that has yet to happen.

[NoWorries]

Certainly a very impressive result GG. So glad to see that you have the Nvidia driver installed.

I have now installed Focal on my HP Laptop which has an AMD Radeon RX Vega M GL / 870 graphics card as well as an Intel HD Graphics 630. At the moment the Intel driver is faster than the AMD Vegam which I have installed.

What I get from glmark2 for these two dirvers is shown below:

~$ env DRI_PRIME=0 glmark2               
=======================================================
  glmark2 2014.03+git20150611.fa71af2d
=======================================================
  OpenGL Information
  GL_VENDOR:     Intel Open Source Technology Center
  GL_RENDERER:   Mesa DRI Intel(R) HD Graphics 630 (Kaby Lake GT2) 
  GL_VERSION:    3.0 Mesa 19.2.1
=======================================================
[build] use-vbo=false: FPS: 3785 FrameTime: 0.264 ms
[build] use-vbo=true: FPS: 4098 FrameTime: 0.244 ms
[texture] texture-filter=nearest: FPS: 3647 FrameTime: 0.274 ms
[texture] texture-filter=linear: FPS: 3497 FrameTime: 0.286 ms
[texture] texture-filter=mipmap: FPS: 3722 FrameTime: 0.269 ms
[shading] shading=gouraud: FPS: 2983 FrameTime: 0.335 ms
[shading] shading=blinn-phong-inf: FPS: 3317 FrameTime: 0.301 ms
[shading] shading=phong: FPS: 3062 FrameTime: 0.327 ms
[shading] shading=cel: FPS: 3030 FrameTime: 0.330 ms
[bump] bump-render=high-poly: FPS: 2212 FrameTime: 0.452 ms
[bump] bump-render=normals: FPS: 3858 FrameTime: 0.259 ms
[bump] bump-render=height: FPS: 3731 FrameTime: 0.268 ms
[effect2d] kernel=0,1,0;1,-4,1;0,1,0;: FPS: 2203 FrameTime: 0.454 ms
[effect2d] kernel=1,1,1,1,1;1,1,1,1,1;1,1,1,1,1;: FPS: 1233 FrameTime: 0.811 ms
[pulsar] light=false:quads=5:texture=false: FPS: 3254 FrameTime: 0.307 ms
[desktop] blur-radius=5:effect=blur:passes=1:separable=true:windows=4: FPS: 1183 FrameTime: 0.845 ms
[desktop] effect=shadow:windows=4: FPS: 2142 FrameTime: 0.467 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 1221 FrameTime: 0.819 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=subdata: FPS: 970 FrameTime: 1.031 ms
[buffer] columns=200:interleave=true:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 1192 FrameTime: 0.839 ms
[ideas] speed=duration: FPS: 2565 FrameTime: 0.390 ms
[jellyfish] <default>: FPS: 2127 FrameTime: 0.470 ms
[terrain] <default>: FPS: 255 FrameTime: 3.922 ms
[shadow] <default>: FPS: 2258 FrameTime: 0.443 ms
[refract] <default>: FPS: 608 FrameTime: 1.645 ms
[conditionals] fragment-steps=0:vertex-steps=0: FPS: 3010 FrameTime: 0.332 ms
[conditionals] fragment-steps=5:vertex-steps=0: FPS: 3059 FrameTime: 0.327 ms
[conditionals] fragment-steps=0:vertex-steps=5: FPS: 2955 FrameTime: 0.338 ms
[function] fragment-complexity=low:fragment-steps=5: FPS: 3035 FrameTime: 0.329 ms
[function] fragment-complexity=medium:fragment-steps=5: FPS: 3065 FrameTime: 0.326 ms
[loop] fragment-loop=false:fragment-steps=5:vertex-steps=5: FPS: 2991 FrameTime: 0.334 ms
[loop] fragment-steps=5:fragment-uniform=false:vertex-steps=5: FPS: 3043 FrameTime: 0.329 ms
[loop] fragment-steps=5:fragment-uniform=true:vertex-steps=5: FPS: 2976 FrameTime: 0.336 ms
=======================================================
                                glmark2 Score: 2614 
=======================================================
~$ env DRI_PRIME=1 glmark2
=======================================================
  glmark2 2014.03+git20150611.fa71af2d
=======================================================
  OpenGL Information
  GL_VENDOR:     X.Org
  GL_RENDERER:   AMD VEGAM (DRM 3.35.0, 5.4.0-4-generic, LLVM 9.0.0)
  GL_VERSION:    4.5 (Compatibility Profile) Mesa 19.2.1
=======================================================
[build] use-vbo=false: FPS: 1986 FrameTime: 0.504 ms
[build] use-vbo=true: FPS: 2353 FrameTime: 0.425 ms
[texture] texture-filter=nearest: FPS: 2288 FrameTime: 0.437 ms
[texture] texture-filter=linear: FPS: 2284 FrameTime: 0.438 ms
[texture] texture-filter=mipmap: FPS: 2259 FrameTime: 0.443 ms
[shading] shading=gouraud: FPS: 2236 FrameTime: 0.447 ms
[shading] shading=blinn-phong-inf: FPS: 2215 FrameTime: 0.451 ms
[shading] shading=phong: FPS: 2213 FrameTime: 0.452 ms
[shading] shading=cel: FPS: 2215 FrameTime: 0.451 ms
[bump] bump-render=high-poly: FPS: 2225 FrameTime: 0.449 ms
[bump] bump-render=normals: FPS: 2349 FrameTime: 0.426 ms
[bump] bump-render=height: FPS: 1471 FrameTime: 0.680 ms
[effect2d] kernel=0,1,0;1,-4,1;0,1,0;: FPS: 2145 FrameTime: 0.466 ms
[effect2d] kernel=1,1,1,1,1;1,1,1,1,1;1,1,1,1,1;: FPS: 1789 FrameTime: 0.559 ms
[pulsar] light=false:quads=5:texture=false: FPS: 2268 FrameTime: 0.441 ms
[desktop] blur-radius=5:effect=blur:passes=1:separable=true:windows=4: FPS: 1069 FrameTime: 0.935 ms
[desktop] effect=shadow:windows=4: FPS: 2101 FrameTime: 0.476 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 1204 FrameTime: 0.831 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=subdata: FPS: 1397 FrameTime: 0.716 ms
[buffer] columns=200:interleave=true:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 1275 FrameTime: 0.784 ms
[ideas] speed=duration: FPS: 1263 FrameTime: 0.792 ms
[jellyfish] <default>: FPS: 2135 FrameTime: 0.468 ms
[terrain] <default>: FPS: 790 FrameTime: 1.266 ms
[shadow] <default>: FPS: 2168 FrameTime: 0.461 ms
[refract] <default>: FPS: 1322 FrameTime: 0.756 ms
[conditionals] fragment-steps=0:vertex-steps=0: FPS: 2347 FrameTime: 0.426 ms
[conditionals] fragment-steps=5:vertex-steps=0: FPS: 1408 FrameTime: 0.710 ms
[conditionals] fragment-steps=0:vertex-steps=5: FPS: 2357 FrameTime: 0.424 ms
[function] fragment-complexity=low:fragment-steps=5: FPS: 1358 FrameTime: 0.736 ms
[function] fragment-complexity=medium:fragment-steps=5: FPS: 2103 FrameTime: 0.476 ms
[loop] fragment-loop=false:fragment-steps=5:vertex-steps=5: FPS: 2345 FrameTime: 0.426 ms
[loop] fragment-steps=5:fragment-uniform=false:vertex-steps=5: FPS: 2339 FrameTime: 0.428 ms
[loop] fragment-steps=5:fragment-uniform=true:vertex-steps=5: FPS: 2344 FrameTime: 0.427 ms
=======================================================
                                glmark2 Score: 1927 
=======================================================

As you can see the Intel card gives 2614 and the AMD card gives 1927. I certainly hope that the AMD driver improves soon. I am beginning to regret choosing a system with an AMD card instead of the Nvidia card. The reason I took this approach was because I believed that AMD provided the interface details. At the moment it doesn't look very promising.

[GreyGeek]

Glad you are now very satisfied with Focal. I am beginning to wonder if you do not select the multimedia option in the installation as for me the Nvidia drivers were always installed with the system.

I have found a good overall test package called glmark2. This tests many graphic aspects. The score that I have from this package is around 2600.

Interesting and thorough test!
My test result was 2725.
It ranged from 4520 for vbo-true to 238 for terrain.

:~$ glmark2
=======================================================
    glmark2 2014.03+git20150611.fa71af2d
=======================================================
    OpenGL Information
    GL_VENDOR:     NVIDIA Corporation
    GL_RENDERER:   GeForce GT 650M/PCIe/SSE2
    GL_VERSION:    4.6.0 NVIDIA 390.116
=======================================================
[build] use-vbo=false: FPS: 4263 FrameTime: 0.235 ms
[build] use-vbo=true: FPS: 4452 FrameTime: 0.225 ms
[texture] texture-filter=nearest: FPS: 3469 FrameTime: 0.288 ms
[texture] texture-filter=linear: FPS: 3441 FrameTime: 0.291 ms
[texture] texture-filter=mipmap: FPS: 3701 FrameTime: 0.270 ms
[shading] shading=gouraud: FPS: 3246 FrameTime: 0.308 ms
[shading] shading=blinn-phong-inf: FPS: 3228 FrameTime: 0.310 ms
[shading] shading=phong: FPS: 3202 FrameTime: 0.312 ms
[shading] shading=cel: FPS: 3203 FrameTime: 0.312 ms
[bump] bump-render=high-poly: FPS: 1903 FrameTime: 0.525 ms
[bump] bump-render=normals: FPS: 3368 FrameTime: 0.297 ms
[bump] bump-render=height: FPS: 4105 FrameTime: 0.244 ms
[effect2d] kernel=0,1,0;1,-4,1;0,1,0;: FPS: 2518 FrameTime: 0.397 ms
[effect2d] kernel=1,1,1,1,1;1,1,1,1,1;1,1,1,1,1;: FPS: 1774 FrameTime: 0.564 ms
[pulsar] light=false:quads=5:texture=false: FPS: 3741 FrameTime: 0.267 ms
[desktop] blur-radius=5:effect=blur:passes=1:separable=true:windows=4: FPS: 1171 FrameTime: 0.854 ms
[desktop] effect=shadow:windows=4: FPS: 1692 FrameTime: 0.591 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 1015 FrameTime: 0.985 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=subdata: FPS: 1133 FrameTime: 0.883 ms
[buffer] columns=200:interleave=true:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 1095 FrameTime: 0.913 ms
[ideas] speed=duration: FPS: 3227 FrameTime: 0.310 ms
[jellyfish] <default>: FPS: 1874 FrameTime: 0.534 ms
[terrain] <default>: FPS: 238 FrameTime: 4.202 ms
[shadow] <default>: FPS: 2655 FrameTime: 0.377 ms
[refract] <default>: FPS: 512 FrameTime: 1.953 ms
[conditionals] fragment-steps=0:vertex-steps=0: FPS: 3291 FrameTime: 0.304 ms
[conditionals] fragment-steps=5:vertex-steps=0: FPS: 3170 FrameTime: 0.315 ms
[conditionals] fragment-steps=0:vertex-steps=5: FPS: 3302 FrameTime: 0.303 ms
[function] fragment-complexity=low:fragment-steps=5: FPS: 3202 FrameTime: 0.312 ms
[function] fragment-complexity=medium:fragment-steps=5: FPS: 3160 FrameTime: 0.316 ms
[loop] fragment-loop=false:fragment-steps=5:vertex-steps=5: FPS: 3202 FrameTime: 0.312 ms
[loop] fragment-steps=5:fragment-uniform=false:vertex-steps=5: FPS: 3206 FrameTime: 0.312 ms
[loop] fragment-steps=5:fragment-uniform=true:vertex-steps=5: FPS: 3194 FrameTime: 0.313 ms
=======================================================
                                  glmark2 Score: 2725

[GreyGeek]

Focal in VB gives the following:

:~$ systemd-analyze
Startup finished in 2.287s (kernel) + 22.323s (userspace) = 24.611s
graphical.target reached after 22.297s in userspace



I installed KDE Neon in VB for grins and giggles. It gives

:~$ systemd-analyze
Startup finished in 4.527s (kernel) + 1.367s (userspace) = 5.895s
graphical.target reached after 1.357s in userspace



However, adding "mesa-utils" to both and testing glxgears, or checking the FTP setting in Desktop effects gave similar resuts: around 1000-1200 fps for glxgears, and 55-60 fps for the KDE FPS test. So the REAL desktop speed will come when I install the NVidia drivers on the bare metal installation.

Since my goal is to go to the next LTS supported Kubuntu release because of its long term stability and support, it will probably finish out my career of using computers. 2025 is a looooong way away, IF my 2012 Acer Aspire V#-771G can last that long. Either way, when it is done I am done using a computer I can type on with all my fingers, as shaky as they are.

[NoWorries]

Glad you are now very satisfied with Focal. I am beginning to wonder if you do not select the multimedia option in the installation as for me the Nvidia drivers were always installed with the system.

I have found a good overall test package called glmark2. This tests many graphic aspects. The score that I have from this package is around 2600.

[GreyGeek]

I went ahead and installed Focal in VB and it is running fine. Very fast for a VB install without my NVidia GT 650M GPU integration. Getting 900-1200 fps with glxgears and the KDE Desktop FPS effects give 55-60 FPS.

[jlittle]

I think the busybox /cdrom directory's name is a historical vestige, from the ISO9660 format used in the iso. It has nothing to do with the hardware or file systems you might have in the PC; I don't think the boot has even looked at the storage present at that point. I haven't had a cdrom drive for about 5 years. busybox hasn't started the main linux kernel yet (AFAICT; the ubuntu isos changed the kernel file name one or two years ago, and busybox gave errors).

Using the iso boot to install a *buntu on a btrfs has no problem; I have done it many times testing the cosmic, disco and eoan betas. oshunluvr's trick of renaming @ and @home keeps the normal, daily driver install out of harm's way. I've risked the integrity of the btrfs on my SSD with various wacky installs, and it has not missed a beat, except for getting a bit full once. Without btrfs subvolumes I'd be juggling partitions.

[GreyGeek]

....
....
Run the command "mount -o loop /cdrom/casper/filesystem.squashfs /filesystem.squashfs"
...

I don't have a /cdrom device because I replaced it with an HDCaddy that holds a 750GB spinner. So, I would probably have to use
"/@/cdrom/casper/filesyste.squashfs filesystem.squashfs"
because of my BTRFS. For example, should I put "/@" in front of the second term or not? Would the booted ISO be on an EXT4 fs or a BTRFS? Are the internal blobs, binaries or scripts confused, or just broken because it doesn't appear to work in Focal for any FS.

Regardless, I don't plan on pursuing this technique because it doesn't appear BTRFS compatible, and you've established that it is not EXT4 compatible without manual intervention, which I have no desire to do. I can burn an ISO rather quickly and both the grub method and the ISO method requires a reboot, so nothing is really gained. I may try VB and then keep it updated until it reaches gold or gets destroyed by a bad upgrade.

Besides, using this kind of Grub boot for an ISO is such a back-burner I doubt that it will be fixed in any reasonable time, if at all. But, the dev folks have surprised us before!

[jlittle]

From a wider focal fossa testing perspective, I'd like to report the iso boot problem, and the workaround, somewhere, somehow, and I've wasted far too much time searching launchpad to find the right way to create a bug. Launchpad seems very oriented around packages, and I don't know what package is involved.

Can anyone tell me the best way to report a problem with the 20.04 iso?

[jlittle]

I'm sorry, I should have checked out what I was suggesting, before I suggested it. Problems with iso booting in the testing phase seem common; in that the eoan daily isos could not iso boot, due to a casper script mismatch, for a long time.

For the focal iso, I stumbled onto a workaround:

1. When one gets the "can't get info on device" busybox error, press control-d.
2. One then gets a different busybox error.
3. Run the command "mount -o loop /cdrom/casper/filesystem.squashfs /filesystem.squashfs"
4. Press control-d.

I don't understand what goes wrong at all. Possibly there's an improved grub incantation for focal to sort the loop device error, but it's a mystery to me.

[GreyGeek]

I've been testing various prefixes to the iso file so that the system can find them from the menuetry setup. All have failed.

So, I read about the grml-rescueboot option:

To use the grml-rescueboot option:

1. [*=left]Install grml-rescueboot
   
   sudo apt-get install grml-rescueboot
   [*=left]Place bootable ISO files in the /boot/grml folder.
   • [*=left]Since this is a system folder, the operation must be conducted as "root". For example, if the ISO is located in the user's Downloads folder, the command would be:
     [*=left]sudo mv ~/Downloads/<filename.iso> /boot/grml/
   
   
   [*=left]Update GRUB
   [*=left]sudo update-grub

It, too, failed, with the same type of error as the previous attempts. Even the system generated boot process can't find what it needs to successfully boot the iso and bring up the desktop.


The problem is in the requirement to use "/@" as the path prefix. You can do that inside 40_custom, as shown above, but the path prefix doesn't stick when the boot process tries to find the loop devices, which should be /@/dev/loop0", since the only way the grub menu can find the iso is with
"set isofile="/@/mnt/iso/focal-desktop-amd64.iso"

Changing any or all of the "loop" references, regardless of which ones or which order, to "/@/dev/loop0", or similar prefixes, and I tried every prefix I could thing of, does not work.

BTW, the iso check sum was verified and I have a live USB stick made from it that boots successfully.