Notes on running a personal Mastodon instance

mastodon-notes.md

Personal Mastodon instance

Effective total cost: $3–4/mo

Setup

Decide on an EC2 instance type:

1. At AWS Console → EC2 → Instance Types, filter for ≥1 GB RAM and sort by price.
   • t3a.micro is lowest.
2. Look up what t3a.micro means:
   • t: general-purpose with a burstable CPU quota
   • 3: the current generation
   • a: AMD
   • micro: the second lowest configuration
3. Calculate cost:
   • $6.89/mo when paying hourly
   • $4.00/mo when paying annually
   • $2.59/mo when paying every 3 years

Prepare your AWS account:

• Set up an alarm for your estimated monthly bill so you're notified early of any unanticipated expenses.
• Import your SSH public key. (EC2 → us-west-2 → Key pairs)

Have ready:

• a domain name and DNS host
• an outgoing mail server
  • I use AWS SES since it's easy (decent reputation, automatic DKIM, etc.) and inexpensive ($0.01/mo), but any SMTP provider will do, and you could also set up a traditional mail server on the EC2 instance.
• static file storage/hosting
  • I use AWS S3 ($0.10/mo), but a variety of providers offer "S3-compatible" service, and you could also just use the filesystem on the EC2 instance. My storage has been growing linearly at 0.65 GB/mo ($0.02/mo²).

Start an EC2 instance:

1. Launch an instance (EC2 → us-west-2 → Instances) with:
   • Image: Ubuntu Server 18.04 LTS (HVM), SSD Volume Type (64-bit x86)
   • Type: t3a.micro
   • Enable termination protection: Yes
   • T2/T3 Unlimited: No
   • Storage: 8 GiB standard (HDD, $0.40/mo)
   • Tags:
     • Name: Mastodon
   • Security Group:
     • Name: mastodon
     • SSH from anywhere
     • HTTP from anywhere
     • HTTPS from anywhere
2. Set up a static IP address and publish an A record at your preferred DNS host.

Prepare the host:

1. SSH in as ubuntu.
2. Add 1 GB of swap:
   1. Make a swap file at /swapfile.
   2. Add a swap entry in /etc/fstab.
   3. Set vm.swappiness=10 in /etc/sysctl.conf.
3. Tune for memory exhaustion:
   1. Set nvm.vfs_cache_pressure=200 in /etc/sysctl.conf.
4. Enable swap compression:
   1. Append zswap.enabled=1 to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub.d/50-cloudimg-settings.cfg.
   2. Run sudo update-grub.
5. Update/upgrade apt packages.
   • If it prompts you to reinstall GRUB, skip that; it has no effect in EC2.
6. Reboot.

Install Mastodon:

1. Follow Mastodon's instructions.
   • To tune PostgreSQL, set:
     • effective_cache_size = 512MB
   • When editing .env.production, pay particular attention to:
     • LOCAL_DOMAIN
     • SINGLE_USER_MODE
     • SMTP…
     • S3… and AWS…
   • When registering services, set:
     • mastodon-sidekiq: --concurrency 1
     • mastodon-streaming: STREAMING_CLUSTER_NUM=1
     • mastodon-web: MAX_THREADS=2 and WEB_CONCURRENCY=1
2. Reboot.
3. Sign in to the web interface and review/configure admin settings.

Try out the setup for a few days/weeks, then commit to a longer payment term:

1. At EC2 → Reserved Instances → Purchase, filter for t3a.micro, sort by effective rate, and purchase a reservation.
2. Wait a few hours for payment processing to complete.
3. At EC2 → Reserved Instances, confirm that the reservation is active.

Backups

borgmatic configuration:

location:
  repositories:
    - …
  atime: false
  source_directories:
    - /home/mastodon/live
  patterns:
    - "+ /home/mastodon/live/.env.production"
    - "! /home/mastodon/live/*"
retention:
  keep_daily: 7
  keep_monthly: 12
hooks:
  postgresql_databases:
    - name: mastodon_production
      username: postgres