Public bug reported: SUMMARY
According to the documentation [1], to set a GRUB parameter in Ubuntu 26.04, use this format: sudo snap set system system.kernel.dangerous-cmdline- append="[parameter]" However, this parameter is ignored. PURPOSE Due to certain firmware or hardware limitations, some computers have to use unusual GRUB parameters. A common one is setting acpi_backlight, something that I've had to do in the past. Currently, on my laptop, I have to set intel_iommu=off for the operating system to be able to access the TPM2 chip. I have to set this if I'm to use TPM-backed FDE in Ubuntu 26.04, which I very much wish to do. If the GRUB parameter is ignored, a number of people won't be able to use Ubuntu once 24.04 reaches end-of-life. I won't be able to use TPM- backed FDE. WHAT SHOULD HAPPEN GRUB should use the parameter in "set system system.kernel.dangerous- cmdline-append" when booting. WHAT DOES HAPPEN GRUB ignores the parameter in "set system system.kernel.dangerous- cmdline-append" when booting. DETAILS When booting the Live USB for Ubuntu 26.04, it's easy to press "e" to edit GRUB, add the required parameter, and continue to boot. This works correctly. It's also possible to interrupt the newly-installed system in the same way. But, it's impossible to set this parameter permanently — there's no way to do this in Ubuntu 26.04 with TPM-backed FDE. • Running update-grub (after modifying /etc/default/grub or for any other reason) results in a borked system (bug #2157702). • Using "set system system.kernel.dangerous-cmdline-append" (as described above) does nothing. Even though set, the parameter is ignored when rebooting. The following commands after rebooting show this: $ sudo snap get system system.kernel.dangerous-cmdline-append intel_iommu=off $ cat /proc/cmdline snapd_recovery_mode=run console=ttyS0,115200n8 console=tty1 panic=-1 quiet splash snapd.xkb="gb,pc105,," [1] https://snapcraft.io/docs/reference/administration/system-options/#system-system-kernel-dangerous-cmdline-append ProblemType: Bug DistroRelease: Ubuntu 26.04 Package: snap (not installed) ProcVersionSignature: Ubuntu 7.0.0-27.27-generic 7.0.6 Uname: Linux 7.0.0-27-generic x86_64 ApportVersion: 2.34.0-0ubuntu2 Architecture: amd64 CasperMD5CheckResult: unknown CurrentDesktop: ubuntu:GNOME Date: Mon Jul 13 14:57:15 2026 ProcEnviron: LANG=en_US.UTF-8 PATH=(custom, no user) SHELL=/bin/bash TERM=xterm-256color XDG_RUNTIME_DIR=<set> SourcePackage: snap UpgradeStatus: No upgrade log present (probably fresh install) ** Affects: snap (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug resolute wayland-session -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2160537 Title: Extra GRUB parameters are ignored when booting Ubuntu 26.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/snap/+bug/2160537/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
