kexec-iso-init: improve hybrid ISO detection and boot param handling by tlaurion · Pull Request #2083 · linuxboot/heads

tlaurion · 2026-04-12T16:59:54Z

Summary

Fixes #2008 - boot hybrid ISOs (PureOS, Ubuntu, Tails, NixOS, Kicksecure, etc.) directly from ISO file on USB without needing to dd the ISO to a raw USB device.

Changes

Tested (works in QEMU/Heads):

kexec-parse-boot.sh: Fix boot entries not appearing for hybrid ISOs
- check_path() no longer fails on ISO-mounted files (FUSE-visible but not kernel-level)
- TAB-indented GRUB configs now parsed correctly
- Leading whitespace stripped before extracting cmd/val
- case $trimcmd → case $cmd in syslinux_entry
- GRUB --- bootloader marker stripped from append params
- syslinux_end handles initrd= via ${param#initrd=}
- set -e exits on normal conditions fixed (grep -q, blkid, etc.)
kexec-parse-bls.sh: Same TAB/whitespace/trim fixes
functions.sh: Skip EFI boot configs (irrelevant on coreboot)
unpack_initramfs.sh: Handle set -e exits
kexec-boot.sh: Fix cmdadd append ordering
kexec-select-boot.sh: Fix initrd path detection

Untested (needs QEMU/hardware boot test):

kexec-iso-init: Inject casper-premount script into ISO initrd
- mounts ISO as loopback at /run/initramfs/iso_mount/ before casper runs
- fixes subshell isolation via /run/initramfs/livemedia.env
- patches casper to source livemedia.env after premount scripts
- creates casper-premount/ORDER so run_scripts executes the script
- passes live-media=$MOUNTED_ISO_PATH (ISO file path)
- passes iso-scan/auto=true

Testing

Parser test harness at tests/iso-parser-test.sh validates all 13 ISOs parse correctly.

Live boot test pending: PureOS 10.3 GNOME on QEMU/Heads — verify these logs:

DEBUG: Successfully injected casper-premount/iso_mount into initrd
Running /scripts/casper-premount → iso_mount script
Should get past "Unable to find a live file system" panic

Copilot

Pull request overview

Adds ISO-on-USB boot compatibility detection and improved UX/logging around kexec-based booting, including documentation of supported ISO behaviors.

Changes:

Add initrd/GRUB scanning and USB filesystem compatibility checks for ISO-file boot, with user warnings on likely failures.
Improve boot option selection UX and display of applied kernel parameter add/remove operations.
Log the final kernel command line in debug output and document the ISO boot flow + compatibility matrix.

Reviewed changes

Copilot reviewed 1 out of 4 changed files in this pull request and generated no comments.

File	Description
initrd/bin/kexec-select-boot.sh	Simplifies menu display and improves confirmation/add/remove parameter UX.
initrd/bin/kexec-iso-init.sh	Adds ISO boot-method detection, USB FS probing, initrd capability heuristics, and broader distro parameter support.
initrd/bin/kexec-boot.sh	Refactors option parsing and adds debug logging of the final kernel cmdline.
doc/boot-process.md	Documents “Stage 2b” ISO-on-USB boot flow and known compatibility results.

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

- Add check_hybrid_iso() using MBR signature at offset 510 (0x55AA) - Add detect_iso_boot_method() to extract boot params from initrd via strings - Add inspect_iso_boot_config() to extract boot params from GRUB configs - Simplify header to document Dracut vs Anaconda boot methods - Use DEBUG level for NOTE/WARN/STATUS spam per logging.md - Change terminal prompts to [Y,d] style with Enter defaulting to yes - Remove Anaconda blocking - let user attempt boot (Qubes R4.3 works) - Keep combined boot params approach (let ISO initrd pick what it needs) Tested with Qubes R4.3 on Q35 QEMU (works). Ref: linuxboot#2083, linuxboot#2008

Add resolve_grub_vars() to substitute GRUB variables like ${iso_path} and ${isofile} with the actual ISO path when extracting boot params from GRUB configs. Fixes boot failure where iso-scan/filename=${iso_path} wasn't being resolved to the actual ISO path. Ref: linuxboot#2083

Add TRACE/DEBUG to understand how boot parameters flow through kexec-boot.sh, especially the cmdline and cmdadd parameters. Ref: linuxboot#2083

- Add check_hybrid_iso() using MBR signature at offset 510 (0x55AA) - Add detect_iso_boot_method() to extract boot params from initrd via strings - Add inspect_iso_boot_config() to extract boot params from GRUB configs - Simplify header to document Dracut vs Anaconda boot methods - Use DEBUG level for NOTE/WARN/STATUS spam per logging.md - Change terminal prompts to [Y,d] style with Enter defaulting to yes - Remove Anaconda blocking - let user attempt boot (Qubes R4.3 works) - Keep combined boot params approach (let ISO initrd pick what it needs) Tested with Qubes R4.3 on Q35 QEMU (works). Ref: linuxboot#2083, linuxboot#2008 Signed-off-by: Thierry Laurion <insurgo@riseup.net>

Add resolve_grub_vars() to substitute GRUB variables like ${iso_path} and ${isofile} with the actual ISO path when extracting boot params from GRUB configs. Fixes boot failure where iso-scan/filename=${iso_path} wasn't being resolved to the actual ISO path. Ref: linuxboot#2083 Signed-off-by: Thierry Laurion <insurgo@riseup.net>

Add TRACE/DEBUG to understand how boot parameters flow through kexec-boot.sh, especially the cmdline and cmdadd parameters. Ref: linuxboot#2083 Signed-off-by: Thierry Laurion <insurgo@riseup.net>

- Add check_hybrid_iso() using MBR signature at offset 510 (0x55AA) - Add detect_iso_boot_method() to extract boot params from initrd via strings - Add inspect_iso_boot_config() to extract boot params from GRUB configs - Simplify header to document Dracut vs Anaconda boot methods - Use DEBUG level for NOTE/WARN/STATUS spam per logging.md - Change terminal prompts to [Y,d] style with Enter defaulting to yes - Remove Anaconda blocking - let user attempt boot (Qubes R4.3 works) - Keep combined boot params approach (let ISO initrd pick what it needs) Tested with Qubes R4.3 on Q35 QEMU (works). Ref: linuxboot#2083, linuxboot#2008 Signed-off-by: Thierry Laurion <insurgo@riseup.net>

Add resolve_grub_vars() to substitute GRUB variables like ${iso_path} and ${isofile} with the actual ISO path when extracting boot params from GRUB configs. Fixes boot failure where iso-scan/filename=${iso_path} wasn't being resolved to the actual ISO path. Ref: linuxboot#2083 Signed-off-by: Thierry Laurion <insurgo@riseup.net>

Add TRACE/DEBUG to understand how boot parameters flow through kexec-boot.sh, especially the cmdline and cmdadd parameters. Ref: linuxboot#2083 Signed-off-by: Thierry Laurion <insurgo@riseup.net>

Fixes linuxboot#2008 - boot hybrid ISOs (PureOS, Ubuntu, Tails, NixOS, Kicksecure, etc.) directly from ISO file on USB without needing to dd the ISO to a raw USB device. Key fixes (TESTED): - kexec-parse-boot: check_path() no longer fails on ISO-mounted files (which exist via FUSE but not at kernel level during initrd execution) - kexec-parse-boot: fix TAB-indented GRUB configs and leading whitespace stripping (sed 's/^[[:space:]]*//' before extracting cmd/val) - kexec-parse-boot: fix case \$trimcmd -> case \$cmd in syslinux_entry (trimcmd includes full line; cmd is just the command word) - kexec-parse-boot: strip GRUB '---' bootloader marker from append params - kexec-parse-boot: syslinux_end handles initrd= via \${param#initrd=} - kexec-parse-boot: fix set -e exits on normal conditions (grep -q, etc.) - kexec-parse-bls.sh: same TAB/whitespace/trim fixes - functions.sh: skip EFI boot configs (irrelevant on coreboot platforms) - unpack_initramfs.sh: handle set -e exits from grep/blkid - kexec-boot.sh: fix cmdadd append ordering in adjust_cmd_line() - kexec-select-boot.sh: fix initrd path detection Key fixes (UNTESTED - needs QEMU/hardware boot test): - kexec-iso-init: inject casper-premount script into ISO initrd (mounts ISO as loopback at /run/initramfs/iso_mount/ before casper runs) - kexec-iso-init: fix subshell isolation via /run/initramfs/livemedia.env (casper's run_scripts runs scripts in subshells; export doesn't propagate) - kexec-iso-init: patch casper to source livemedia.env after premount - kexec-iso-init: create casper-premount/ORDER so run_scripts executes script - kexec-iso-init: pass live-media=\$MOUNTED_ISO_PATH (ISO file path) - kexec-iso-init: pass iso-scan/auto=true Signed-off-by: Thierry Laurion <insurgo@riseup.net>

…m support - Add scan_initramfs() to detect filesystem drivers (ext4, vfat, exfat, etc.) and boot methods (iso-scan, live-media, boot=live, boot=casper, etc.) - Add detect_initrd_boot_support() to scan initrds from parsed boot entries - Add extract_boot_params_from_cfg() to scan *.cfg files for boot params - Warn if USB filesystem is not supported by ISO initramfs - Warn if no boot method detected, offer to try anyway - Keep ADD params matching origin/master (fromiso=/dev/disk/by-uuid/...) Signed-off-by: Thierry Laurion <insurgo@riseup.net>

- Use unpack_initramfs.sh to extract initrds - Detect what boot params each ISO's initramfs understands - Show init script name and relevant lines for debugging Signed-off-by: Thierry Laurion <insurgo@riseup.net>

Add live-media=/dev/disk/by-uuid/.../path/to/iso.iso and live-media-path=casper to ADD params. PureOS casper initramfs needs live-media= pointing to the ISO file path, not /boot. This complements existing fromiso=, iso-scan/filename=, img_loop=, and iso= params. Signed-off-by: Thierry Laurion <insurgo@riseup.net>

- Fix duplicate iso-scan/filename parameter injection - Add deduplication to cfg boot method extraction - Add selective parameter injection (boot=live, boot=casper, live-media) - Add header comments to kexec-iso-init.sh, kexec-parse-boot.sh, kexec-boot.sh - Add param injection validation to test suite - Fix Tails boot parameter regression (was injecting boot=casper incorrectly) - Show boot params in boot menu options

tlaurion · 2026-04-22T17:31:31Z

this is way too complex. look at u-root/u-root#3578

- Simplify parameter injection to always inject iso-scan/filename as primary - Add installer ISO detection (warns user to use dd instead) - Remove Ventoy recommendations (not supported by Heads) - Keep USB filesystem check from initrd scanning

- Add ISO boot documentation to development.md - Fix kexec-parse-boot.sh path in sim_iso_menu.sh

Copilot AI review requested due to automatic review settings April 12, 2026 16:59

Copilot started reviewing on behalf of tlaurion April 12, 2026 17:00 View session

Copilot AI reviewed Apr 12, 2026

View reviewed changes

tlaurion force-pushed the iso-boot-detection branch from b4b1383 to cb30626 Compare April 12, 2026 17:04

tlaurion changed the title ~~initrd: add ISO boot detection, USB filesystem validation, and distro kernel params~~ initrd: add ISO boot detection and USB filesystem validation Apr 12, 2026

tlaurion force-pushed the iso-boot-detection branch 2 times, most recently from d810864 to d5b268c Compare April 12, 2026 19:43

tlaurion marked this pull request as draft April 12, 2026 19:43

tlaurion force-pushed the iso-boot-detection branch from 29fb8da to ab2fc17 Compare April 12, 2026 20:14

tlaurion closed this Apr 13, 2026

tlaurion force-pushed the iso-boot-detection branch from ab2fc17 to 8f78967 Compare April 13, 2026 00:32

tlaurion changed the title ~~initrd: add ISO boot detection and USB filesystem validation~~ kexec-iso-init: improve hybrid ISO detection and boot param handling Apr 13, 2026

tlaurion reopened this Apr 13, 2026

tlaurion force-pushed the iso-boot-detection branch from 90f3faf to 16b9805 Compare April 13, 2026 00:44

tlaurion added enhancement / improvement UX Bounty/Donations expected Work could/should be funded by interested stakeholder feature freeze 2026-04 installation labels Apr 13, 2026

This was referenced Apr 13, 2026

"kicksecure iso doesn't boot under Heads #2008

Open

kexec-iso-init: inject casper-premount script to mount ISO as loopback #2084

Closed

tlaurion force-pushed the iso-boot-detection branch from 594c17f to f17cf57 Compare April 15, 2026 18:04

tlaurion added 7 commits April 21, 2026 13:22

kexec-boot.sh: add DEBUG traces for cmdline and cmdadd

9e318a6

Add TRACE/DEBUG to understand how boot parameters flow through kexec-boot.sh, especially the cmdline and cmdadd parameters. Ref: linuxboot#2083 Signed-off-by: Thierry Laurion <insurgo@riseup.net>

tests: enhance iso-parser to detect initramfs boot params

d68ec25

- Use unpack_initramfs.sh to extract initrds - Detect what boot params each ISO's initramfs understands - Show init script name and relevant lines for debugging Signed-off-by: Thierry Laurion <insurgo@riseup.net>

tlaurion force-pushed the iso-boot-detection branch from f17cf57 to ca51e23 Compare April 22, 2026 17:50

WIP: Update docs and sim_iso_menu path fix

a2f9305

- Add ISO boot documentation to development.md - Fix kexec-parse-boot.sh path in sim_iso_menu.sh

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

kexec-iso-init: improve hybrid ISO detection and boot param handling#2083

kexec-iso-init: improve hybrid ISO detection and boot param handling#2083
tlaurion wants to merge 10 commits intolinuxboot:masterfrom
tlaurion:iso-boot-detection

tlaurion commented Apr 12, 2026 •

edited

Loading

Uh oh!

Copilot AI left a comment

Uh oh!

tlaurion commented Apr 22, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Uh oh!

Conversation

tlaurion commented Apr 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

Changes

Tested (works in QEMU/Heads):

Untested (needs QEMU/hardware boot test):

Testing

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

tlaurion commented Apr 22, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

tlaurion commented Apr 12, 2026 •

edited

Loading