Bitcoin Core disk full on Umbrel OS — 1TB SSD not enough anymore?

I was running a Bitcoin Core node on Umbrel OS on a 1TB SSD and ran into a disk space issue near the end of the initial sync. The node was already at around height 952,967 (~99.9% synced) when it suddenly stopped with a “No space left on device” error while writing to the txindex database. After checking disk usage with df -h, I found the main partition /dev/sda1 mounted at /mnt/data was completely full (938GB total, 891GB used, 0GB available), which caused Bitcoin Core to shut down to avoid corrupting the LevelDB database.

To investigate further, I checked the Bitcoin data directory using du -sh, which showed that most of the space was consumed by the blockchain itself: blocks was ~792GB, chainstate ~12GB, and indexes ~78GB (including a ~66GB txindex and ~13GB block filters). I also confirmed that Docker usage was minimal (docker system df showed only ~3.8GB total), so the issue was clearly the Bitcoin data size combined with the filesystem reserve. I then checked the ext4 reserved space using tune2fs -l /dev/sda1 | grep 'Reserved block count', which showed a 5% reservation (~47GB), further limiting usable space for the node during sync operations.

The solution I applied was reducing the ext4 reserved space from 5% to 1% using the command sudo tune2fs -m 1 /dev/sda1. After applying this change, I verified the disk again with df -h /mnt/data, which now showed about 39GB of available space (938GB total, 891GB used, 39GB available, 96% usage). This gave the system enough breathing room to continue operating. The node could then proceed without immediately hitting disk full errors again. The root cause is that a full archival Bitcoin node with txindex enabled on a 1TB SSD in 2026 leaves almost no operational buffer, especially during final sync stages where LevelDB needs extra temporary space to write and reorganize data.

I would recommend anyone using a 1TB drive to store the Bitcoin blockchain to regularly check whether their node is still able to sync properly and whether there is enough free disk space for ongoing operations.