25.10 Installer: Missing Support For DM Devices / Cannot Re-use Its Own Partioning Scheme

[Maddes]

Tested Ubuntu 25.10, but when reinstalling than the installer cannot reuse its own previous partioning scheme in manual installation.

#1 Initial setup of Ubuntu 25.10:
* UEFI with Secure Boot enabled
* Booting Ubuntu 25.10 ISO via Ventoy 1.1.7
* Installation via "Erase disk and install Ubuntu"
* Choosing "Encrypt with a passphrase" (LVM on LUKS)

Created GPT partition scheme:
1. EFI Systen Partition (ESP), 1 GiB, EF00, VFAT, /boot/efi
2. Boot Partition, 2 GiB, 8300, ext4, /boot
3. LUKS Partition, Rest of NVM disk, /dev/mapper/dm_crypt-0
   > LVM, VG ubuntu-vg
     > Root Partition, LV ubuntu-lv, ALL of VG!, ext4, /

Boots and works well.

#2 Re-installation
* Boot same as above
* Installation via "Manual Installation"
* Installer Issues:
  * Installer cannot open LUKS partition
  * Even when manually opening the LUKS partition, LVM got detected automatically and restarting the installer, then the LV still is not listed during "Manual Installation"

Installer does not detect available DM devices, and therefore cannot handle them.

Conclusion:
Ubuntu installer does not support common devices under "Manual Installation". Rendering it useless for most cases.

Expectation:
Support at least the DM devices under "Manual Installation" that are created via "Erase disk and install Ubuntu".
Possible workaround, provide a target directory where the user can mount his wanted devices, then install under target, and allow user to do the last fine-tuning (chroot, apt install, config files)

ProblemType: Bug
DistroRelease: Ubuntu 25.10
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 6.17.0-5.5-generic 6.17.0-rc7
Uname: Linux 6.17.0-5-generic x86_64
NonfreeKernelModules: zfs
ApportVersion: 2.33.1-0ubuntu3
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 25.10.2
CloudArchitecture: x86_64
CloudID: nocloud
CloudName: unknown
CloudPlatform: nocloud
CloudSubPlatform: seed-dir (/var/lib/cloud/seed/nocloud)
CurrentDesktop: ubuntu:GNOME
Date: Fri Nov 28 17:56:15 2025
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz --- quiet splash
LiveMediaBuild: Ubuntu 25.10 "Questing Quokka" - Release amd64 (20251007)
ProcEnviron:
 LANG=C.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
SourcePackage: ubiquity
Symptom: installer
UpgradeStatus: No upgrade log present (probably fresh install)

[mickse (mickse5566)]

This looks like a clear installer limitation with Ubuntu 25.10, especially concerning LUKS + LVM setups during manual installation. Since the installer isn’t recognizing previously created DM/LUKS devices, it can’t properly reuse encrypted partitions—something that definitely should be supported. Until Ubuntu updates the installer, the only real workaround is manually unlocking LUKS, activating LVM, and doing a custom chroot-based install, which isn’t ideal for most users.

Hopefully the devs address this soon, because it affects anyone reinstalling with encryption.

And on a lighter note, if you need a break from debugging, Morgan Wallen Gainesville is trending as a must-see event! https://morganwalentickets.com/morgan-wallen-gainesville-fl/