3

How do I prevent mist from ever downloading the blockchain?

I have a small HDD and can't afford the disk space.

6

Using parity

You can have parity emulate geth's IPC (ie, pretend to be geth), by running:

parity --light --geth

If you want to be lazy, you can add to your configuration file:

[parity]
light = true
geth = true

Then start mist as:

mist  --syncmode light

If you get a blank screen when mist loads, see here.

5

Usinggeth

Running geth --light will not download the blockchain, but instead query other nodes for any information contained in the blockchain.

It took me quite a bit of investigation to work out how to use mist with geth --light, but the answer is to first start geth:

geth --light

Then start mist, telling it to use the node in light mode:

mist  --syncmode light

You should be able to just run mist --node-light, but this issue is currently preventing it.

As a work-around for linux users, based on @pparent76's script, I came up with:

#!/bin/bash
# Work around for issues:
# https://github.com/ethereum/mist/issues/2254
# https://github.com/ethereum/mist/issues/2372
# https://github.com/ethereum/mist/issues/2999
set -eu # For script robustness
geth=$(which geth)
mist=$(which mist) # Change to explicit path if you call this script "mist"

# Use pidof as procps' pgrep is broken:
# sleep 1& pgrep -ax '^sleep$' should return null
if ! geth_pid=$(pidof geth); then
  echo "Starting $geth."
  "$geth" --syncmode light &
else
  echo "Geth is already running with PID(s): $geth_pid"
fi

if ! mist_pid=$(pidof mist); then
  echo "Starting $mist."
  "$mist" --light-node
else
  echo "Mist is already running with PID(s): $mist_pid"
fi

Call the script "emist" so it doesn't recursively call itself :)


Bonus safety seatbelt:

Since geth doesn't support a startup file, you may want to ensure that geth will not start without using --light.

Ensure geth cannot create a lock file on the blockchain database:

rm -rf ~/.ethereum/geth/chaindata/ && mkdir -m 000 ~/.ethereum/geth/chaindata/

This will remove any already downloaded blockchain data, and recreate the directory without write permissions.

In Windows, you can remove the write permissions for the current user by right-clicking on the chaindata directory, selecting "Properties" then "Permissions" and unticking "write" permissions for the current user.

If I then try to run geth without --light, I get:

Fatal: Error starting protocol stack: open /home/ravi/.ethereum/geth/chaindata/LOCK: permission denied

This is desirable because it:

  • Prevents any blockchain download
  • Reminds me to run geth with --light
  • Ensures that I don't need clean up any partially downloaded blockchain data.

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