Purging unused Mastodon accounts

I run my own Mastodon instance at isaacsu.com. (Not anymore) Over time, it accumulates avatar and header files of accounts that I do not care about in the live/public/system/accounts directory, and it gets quite large.

Here’s a Rails console script that I use to purge them every now and again. There’s one method unused_accounts that tries to assemble a whitelist of account_ids that I’ve ever interacted with and returns a list of accounts that are not them.

1. Start by booting up Rails console for mastodon

cd ~/live
RAILS_ENV=production bundle exec rails console

2. Define the unused_accounts method

Paste this code block into Rails console.

def unused_accounts
  favourites = Favourite.all
      .map{ |f| f.account_id }
  favourite_statuses = Favourite.all
      .map{ |f| [f.status.account_id, f.status.in_reply_to_account_id] }
  follows = Follow.all
      .map{ |f| [f.account_id, f.target_account_id] }
  notifications = Notification.all
      .map{ |n| [n.account_id, n.from_account_id] }
  poll_votes = PollVote.all
      .map{ |p| p.poll.account_id }

  activities = (favourites + favourite_statuses + follows + notifications + poll_votes)

  replied = Status.where(account_id: activities, reply: true)
      .map{ |s| s.in_reply_to_account_id }

  reblogged = Status.where(account_id: (activities+replied).reject(&:nil?), reply: true)
      .reject{ |s| s.reblog_of_id.nil? }
      .map{ |s| Status.find(s.reblog_of_id).account_id }

  all = (activities + replied + reblogged).reject(&:nil?).uniq

  Account.where.not(id: all)

3. Suspend them

Paste this code block into Rails console.

unused_accounts.each do |account|
  puts "#{account.username} #{account.domain}"
  SuspendAccountService.new.call(account, destroy: true)

A most recent run freed up 4GB of disk space. bin/tootctl media remove --days=5 helped reclaim another ~3GB on top of that.

Hope someone else finds this useful. I should note that this worked on Mastodon v2.9.2. There’s no guarantee that it will work in future or past versions.