Update system notes

These are notes on how the Cardano wallet launcher and update system currently work.

Old Design


This is the frontendOnlyScenario from cardano-sl/tools/src/launcher/Main.hs. Do not worry about serverScenario - replace it completely.

The Daedalus install is always configured to run the launcher in frontendOnlyMode. The other code (clientScenario) is dead code. The diagram describes frontendOnlyMode, which goes through the node-ipc system.


Running the update system

The very first thing that cardano-launcher does, before starting the frontend, is check for a previously downloaded update.

If there is a file at updaterPath, it runs the updater, which is a bit wrong.

There are two code paths, depending on whether launcher is running on Windows.

macOS and Linux

To run the updater on non-Windows systems, it will spawn ${updaterPath} ${updaterArgs} ${updateArchive}.

After the update subprocess exits successfully, it hashes the updateArchive file, checks that the wallet database has this hash, then deletes the updateArchive file.


To run the updater on Windows systems, it will create a .bat file then execute it. The temporary .bat file runs the following steps:

  1. Kill the cardano-launcher process with TaskKill /PID

  2. Run the downloaded installer for the new version.

  3. Delete the installer file.

  4. Run cardano-launcher with the same command line arguments that the previous launcher was run with.

  5. Delete the .bat file.

Starting Daedalus

Daedalus is started by running Electron, with the main Javascript file being in a subdirectory (the exact filename is configured by the main key of package.json)

The Daedalus Window title bar is configured using the productName key of package.json.

Daedalus uses a number of variables at runtime.

Variable Description Set by
NETWORK Used to show the user what network Daedalus is Build
connecting to. One of mainnet, staging, testnet.
REPORT_URL The base URL for posting Daedalus automatic bug Build
API_VERSION Used to show the Cardano version in the About box. Build
LAUNCHER_CONFIG Path to a launcher config YAML file. Launcher

The variables listed as being set by “Build” are in fact hard-coded using string substitution at installer build-time, but this need not be the case.

Starting cardano-node

Daedalus spawns the cardano-node process using child_process. The command-line parameters are built from the file specified by LAUNCHER_CONFIG.

After starting the cardano-node process, it then uses the nodejs API to pass “messages” to the subprocess (see cardano-sl/node-ipc/src/Cardano/NodeIPC.hs).

Applying updates

To apply an update, cardano-launcher just loops back to the start, where the update system will immediately run.

Update server

The update server is a S3 bucket managed by devops, accessible by HTTPS. Before proposing an update on the blockchain, the installer files are uploaded to the updates bucket, named with their Blake2b hash.

As an example: the testnet update server

New design

The old design can be simplified and improved on. At the very least, dead code should be removed.


In scope for cardano-shell

  • Handles updating the software when Daedalus user clicks “Yes” to apply a new update (in current design, this means responding when Daedalus exits with status 20).

  • Responds correctly when Daedalus exits with status 21 or 22.

  • Works on Windows. Note the possible portability issues surrounding:

    • Output redirection

    • Exclusive file locking

    • Paths

    • Killing processes

    • Different installation methods

  • Daedalus is able to handle the wallet node crashing. The wallet node is able to restart after crashing.

  • Works well for Daedalus development.

  • Multiple Daedalus instances for different networks can run at the same time. Automatic updates for one network do not interfere with a Daedalus instance running on another network.

New requirements

  • Works on Linux for single-file executable containers such as AppImage or Snap. These executable formats require that the cardano-launcher process be terminated and restarted for updates.

  • All code is the same regardless of network, and the network is selectable as a command line option.

  • No more launcher YAML file.

  • Launcher code has automatic tests which are executed on all target platforms.

Out of scope for cardano-shell

  • Update system for nodes which aren’t running inside Daedalus. For example, exchange wallets and staking nodes. These users will handle updating their node software.

  • Sending node crash reports to report-server. Nobody looks at these. Daedalus has its own crash reporting feature.

  • Running multiple cardano-node backends at the same time within a single instance of Daedalus.

  • Switching between networks at runtime.


  • Is it necessary to have two processes cardano-launcher and cardano-node, or can they be combined?

  • Is there a more “standard” way for electron apps to start their backend servers?