Swap is force-recreated every ~2 hours by DAppNode host scripts

[daferna]

Swap is force-recreated every ~2 hours by DAppNode host scripts, which breaks validator block proposals.

Setup: DAppNode host, 32 GB RAM, Besu + Nimbus + Web3Signer, 7 mainnet keys.

I missed a proposal because the host was swapping (~5 GB of 16 GB /swapfile in use) while Besu was importing a heavy block and Nimbus timed out signing a blinded builder block (Unable to sign blinded block proposal using remote signer reason="Operation timed out"). Besu docs explicitly say to disable swap on a validator.

I then:

• Commented swap out of /etc/fstab
• swapoff /swapfile
• systemctl mask swapfile.swap (/etc/systemd/system/swapfile.swap -> /dev/null)

None of that sticks. /swapfile is recreated and swapon’d about every 2 hours:

• 2026-09-01 21:12:20 UTC — kernel: Adding 16777212k swap on /swapfile
• 2026-09-01 23:12:11 UTC — file born; 23:12:19 — swapon again
  stat: Size 17179869184, mode 0600, root:root

swapfile.swap then shows as masked + active, because systemd sees the file in /proc/swaps. The mask is doing its job. Something else calls swapon(2) on the host.

That something is your own scripts:

/usr/src/dappnode/scripts/dappnode_install.sh
  fallocate -l ${SWAP}k /swapfile
  mkswap /swapfile
  swapon /swapfile
  echo '/swapfile none swap defaults 0 0' >> /etc/fstab

/usr/src/dappnode/DNCORE/scripts/upgrade/add_swap.sh
  dd if=/dev/zero of=/swapfile bs=1M count=$mb
  mkswap /swapfile
  swapon /swapfile
  echo "/swapfile swap swap defaults 0 0" >> /etc/fstab

add_swap.sh is clearly “if swapon --show is empty, build a 16G file and enable it.” There is no timer named swap in systemctl list-timers, no crontab, and no DNCORE compose volumes: for /swapfile. A short-lived privileged --rm container (not listed in docker ps -a) is almost certainly how dappmanager/core invokes this on the host. Wifi is the only core compose with privileged: true; it does not mention swap.

This is a bad default for a staking box:

1. You fight the operator. Mask + fstab is the documented way to disable swap. You overwrite it.
2. You append another fstab line every successful run.
3. On 32 GB + Besu/RocksDB, swap turns a 200ms import into multi-second stalls and misses proposals. I had a clean proposal the next day after heap/governor fixes and swap off — until you turned swap back on.
4. There is no UI toggle, no env var, no “I am a validator, do not touch swap.”

Ask:

• Stop auto-creating /swapfile when the operator has masked swapfile.swap or removed it from fstab.
• Expose an explicit setting: DAPPNODE_ENABLE_SWAP=false (or host UI) that add_swap.sh honors.
• Do not >> /etc/fstab on every run.
• Document that staking nodes should run without swap.

I have stubbed add_swap.sh to exit 0 and replaced /swapfile with an immutable directory so the next 2-hour job fails closed. I should not have to vandalize your upgrade scripts to keep a validator safe.

Happy to provide full journal slices and stat output.