Crash during manual partitioning: ValueError: Mountpoint is not specified due to leftover BTRFS subvolumes with None paths.

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
linux, python
Domain
cli, operating-systems

Research direction

Start by tracing the _mount_btrfs_subvol path used by manual partitioning and the handling of existing BTRFS subvolumes whose paths are None. Reproduce the failure with a leftover BTRFS partition and Wipe: True, then verify that invalid subvolumes no longer cause the installer to raise ValueError before wiping or formatting the partition.

Written by the indexing model from the issue text.

Description

Which ISO version are you using?

2026-02-26

The installation log
-
describe the problem

When attempting to install Arch Linux using archinstall on a disk that contains a leftover BTRFS partition from a previous failed installation, the installer crashes with a ValueError: Mountpoint is not specified in _mount_btrfs_subvol.
​This crash occurs even if Wipe: True is explicitly selected for that partition in the manual partitioning menu. It appears that the installer attempts to read and parse the existing broken BTRFS subvolumes (which show up with None as their path/mountpoint in the menu) before performing the actual wipe/format operation. Since it doesn't know how to mount a subvolume with a None path, it throws an exception and aborts the installation entirely

Exiting archinstall and manually running wipefs -a /dev/nvme0n1pX on the problematic partition completely removes the leftover subvolumes. After doing this, running archinstall again and configuring the partition works perfectly. The installer should ideally ignore or wipe these invalid subvolumes automatically when Wipe: True is flagged.

​Hardware / Environment:
​Device: Laptop
​CPU: AMD Ryzen 5 4600H
​GPU: NVIDIA GTX 1650
​RAM: 16GB DDR4 3200MHz
​Setup: Dual boot with Windows on a single NVMe drive.Exiting archinstall and manually running wipefs -a /dev/nvme0n1pX on the problematic partition completely removes the leftover subvolumes. After doing this, running archinstall again and configuring the partition works perfectly. The installer should ideally ignore or wipe these invalid subvolumes automatically when Wipe: True is flagged.

​Hardware / Environment:
​Device: Laptop
​CPU: AMD Ryzen 5 4600H
​GPU: NVIDIA GTX 1650
​RAM: 16GB DDR4 3200MHz
​Setup: Dual boot with Windows on a single NVMe drive.

Dominant language
Python
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