Please add loopback.cfg

[probonopd]

Issue/Bug Description:

Please add a loopback.cfg like Ubuntu ISOs do. This will allow one to boot the ISO from hard disk in an easy way.

Other Notes:

https://www.supergrubdisk.org/wiki/Loopback.cfg

[probonopd]

Ran into this again today. Please add loopback.cfg. I had to use an entire USB drive today just to boot Pop!OS, whereas I'd have loved to just add it to GRUB like shown above.

[queeup]

No loopback on 20.04 either. 😞

[space88man]

Pop_OS! ISO Casper doesn't containing parsing for iso-scan/filename=.

# on Pop_OS! initrd.gz
$ grep -r 'iso-scan' init scripts/
$

# on Ubuntu Desktop initrd.gz
$ grep -r 'iso-scan' init scripts/
scripts/casper-premount/20iso_scan:        iso-scan/filename=*)
scripts/casper-premount/20iso_scan:            iso_path=${x#iso-scan/filename=}

[probonopd]

Thanks for checking @space88man. Then it should be brought over from Ubuntu. It's in the package https://packages.ubuntu.com/eoan/lupin-casper.

[space88man]

TL;DR you need a slightly modified initrd.gz to run in ISO-on-HDD mode by adding casper's iso-scan scripts.

Tested - I extracted initrd.gz and add /scripts/casper-premount/* and /scripts/lupin-helpers from the Ubuntu desktop ISO then rebuilt initrd.gz.

Instead of using GRUB's loopback, I pulled vmlinuz and the new initrd.gz to the HDD and referenced them in the GRUB menu entry in place of (loop)/casper/vmlinuz etc. Now

... boot=casper iso-scan/filename=/pop-os_20.04_amd64_intel_13.iso uuid=2020-08-31-22-41-10-00 ...

works and Pop_OS! is able to run in ISO-on-HDD mode. I add the uuid= to be doubly sure, since my HDD has partitions with extracted ISOs for Ubuntu, KDE Neon, etc — didn't want casper to choose the wrong live image.

Off-topic: How did Pop_OS! 20.04 run on my Renoir APU when KDE Neon (latest 5.4.0) wouldn't and required nomodeset?

[jrudolph]

TL;DR you need a slightly modified initrd.gz to run in ISO-on-HDD mode by adding casper's iso-scan scripts.

That works indeed. After adding 20isoscan to scripts/casper-premount, I also had to add an entry to the scripts/casper-premount/ORDER file.

[probonopd]

So, can a loopback.cfg be added to the official ISOs please?

[Oifan]

I highly doubt Pop!_OS will have a working loopback.cfg this year.

[jackpot51]

This seems like something any one of you could help fix with a PR. Add lupin-casper to the LIVE_PKGS in each config/pop-os file and create loopback.cfg in mk/iso.mk

[VPraharsha03]

TL;DR you need a slightly modified initrd.gz to run in ISO-on-HDD mode by adding casper's iso-scan scripts.

Tested - I extracted initrd.gz and add /scripts/casper-premount/* and /scripts/lupin-helpers from the Ubuntu desktop ISO then rebuilt initrd.gz.

Instead of using GRUB's loopback, I pulled vmlinuz and the new initrd.gz to the HDD and referenced them in the GRUB menu entry in place of (loop)/casper/vmlinuz etc. Now

... boot=casper iso-scan/filename=/pop-os_20.04_amd64_intel_13.iso uuid=2020-08-31-22-41-10-00 ...

works and Pop_OS! is able to run in ISO-on-HDD mode. I add the uuid= to be doubly sure, since my HDD has partitions with extracted ISOs for Ubuntu, KDE Neon, etc — didn't want casper to choose the wrong live image.

Off-topic: How did Pop_OS! 20.04 run on my Renoir APU when KDE Neon (latest 5.4.0) wouldn't and required nomodeset?

@space88man @jrudolph can you share the full list of commands you used to extract & re-compress the gz because i'm missing some of the files when decompressing and on re-compressing; they aren't identical on comparing (i'm doing it for pop os 19.04)

[Oifan]

Following commands assume the content of initrd.gz is (will be) in the current directory (taken from Slackware + kernel.org):

• extract: gzip -cd /tmp/initrd.gz | cpio -imd
• compress: find . | cpio -o -H newc | gzip -9c > /tmp/initrd-new.gz

[VPraharsha03]

Following commands assume the content of initrd.gz is (will be) in the current directory (taken from Slackware + kernel.org):

• extract: gzip -cd /tmp/initrd.gz | cpio -imd
• compress: find . | cpio -o -H newc | gzip -9c > /tmp/initrd-new.gz

@Oifan Extraction follows a different sequence of cpio and gzip commands, but this can be avoided and directly unmkinitramfs can be used to extract everything in a go easily....

problem is some of the files do not get extracted (i've tried on different filesystems - NTFS & ext3 but they don't extract) - these files are from lib\firmware\radeon\

not sure if others have faced this issue or not

[space88man]

For reference Pop_OS! 21.04 build 10; build initrd with iso-scan capability:

# figure out the sizes of microcode for skip=NNNN and count=NNNN needed later
dd if=SRC/initrd.gz | cpio -it # will show size of microcode 1, say 62
.
kernel
kernel/x86
kernel/x86/microcode
kernel/x86/microcode/AuthenticAMD.bin
62 blocks

dd if=SRC/initrd.gz skip=62 | cpio -it # will show size of microcode 2, say 9004
kernel
kernel/x86
kernel/x86/microcode
kernel/x86/microcode/.enuineIntel.align.0123456789abc
kernel/x86/microcode/GenuineIntel.bin
9004 blocks

In the following comands we assume 9066 blocks for prepended microcode.

# extract initrd, need to skip AMD(62 blocks)/Intel microcode(9004 blocks)
# YMMV as the block sizes will change
dd if=SRC/initrd.gz skip=9066 | cpio -imd

# now fixup scripts/casper-premount/{20iso_scan,ORDER} scripts/lupin-helpers
# from ubuntu 21.10 (has an extra unneeded 30* script so adjust ORDER accordingly)

# reconstruct a initrd with microcode prepended
dd if=SRC/initrd.gz count=9066 > DEST/initrd-new.gz
find . | cpio -o -H newc | lz4 -l -c >> DEST/initrd-new.gz

The /scripts/casper/pre-mount/ORDER file:

/scripts/casper-premount/10driver_updates "$@"
[ -e /conf/param.conf ] && . /conf/param.conf
/scripts/casper-premount/20iso_scan "$@"
[ -e /conf/param.conf ] && . /conf/param.conf

Files after copying stuff from the Ubuntu 21.10 initrd:

$ ls   scripts/lupin-helpers scripts/casper-premount/
scripts/lupin-helpers

scripts/casper-premount/:
10driver_updates  20iso_scan  ORDER