The Goal:

Deploying a Relay Chain with Custom Validator Keys, that a Parachain can start collation successfully.

The Issue:

Using the key subcommand in the Relay, I wasn't able to properly insert the Session Keys to the Relay nodes' keystore.

The Relay with 2 validators was working fine, producing and finalizing blocks, but when I deployed a Parachain it outputted a WARN: collation wasn't advertised to any validator.

And it started to output the WARN for 5 minutes +- until it started to output an error. Finally I haven't found any mention whatsoever in how to do so.

  • 1
    I read your comment about using --alice, I think something could be wrong in the chain-spec. Can you trying with zombienet (github.com/paritytech/zombienet) ?
    – pepoviola
    Commented Oct 18, 2022 at 13:14
  • 1
    Deleting the question text makes the post not that valuable :/ please do update or delete yge post completely?
    – Nuke
    Commented Oct 20, 2022 at 22:46
  • 1
    Would you mind providing the solution anytime soon? We have the same issue, asked here: substrate.stackexchange.com/questions/5696/… Commented Nov 4, 2022 at 14:49
  • 1
    I've submitted the solution, soon they'll review and approve so you can solve your problem as well. Commented Nov 7, 2022 at 16:11
  • 1
    Thanks @AlexandreRibeiro 😻
    – Nuke
    Commented Nov 7, 2022 at 17:32

2 Answers 2


The Solution:

After trying a lot of things, I've found from an RPC call that there's 7 keys needed for each Validator node. Those are, gran babe imon para asgn audi beef. And for each key-type there's a scheme, there's a table to reference.

Key-Type Scheme
gran ed25519
babe sr25519
imon sr25519
para sr25519
asgn sr25519
audi sr25519
beef ecdsa

Insert them like this,

./target/release/polkadot key insert \
--base-path <path for this validator> \
--chain <raw relay chainSpec> \
--scheme <see table> \
--suri "<mnemonic of this validator>" \
--key-type <see table>

Pay attention to the base-path you're choosing, you need separate paths for different validators. And to each path, you insert 7 keys using the same validators' private seed.

Parachain Session Keys:

In the Para, run the node and specify a RPC port to make a call later on.

./target/release/<parachain binary> --collator \
--force-authoring \
--chain <raw parachainSpec> \
--base-path /tmp/<para>/<path> \
--port 40333 \
--ws-port 8844 \
--rpc-port 9022 \
--unsafe-ws-external \
--rpc-methods=unsafe \
--rpc-external \
--rpc-cors=all \
-- \
--execution wasm \
--chain relay-raw.json \
--port 30343 \
--ws-port 9977 \
--bootnodes /ip4/<relay bootnode ip>/tcp/30333/p2p/<bootnode peerId>

Using this command as an example, the port open for RPC was 9022 so the insert key call should be:

curl -vH 'Content-Type: application/json' --data '{ "jsonrpc":"2.0", "method":"author_insertKey", "params":["aura", "<private seed in hex>", "<public key in hex>"],"id":1 }'

The private and public key here should be the collator keys. And it's for aura. So it is using the sr25519 scheme.

And it's output:

* Connection #0 to host left intact

I think this warning is not related to the session keys. Try add more validators to the relaychain.

And if you are using --alice or something like that. You don't need to insert the key manually. These are well-known keys.

And if you want to insert your custom keys, check the runtime session keys configurations.


Let's take parachain-template as an example. As you can see from the link, you only need to insert the Aura key.

  • When I used the --alice flag on the parachain, I didn't insert the keys manually. I'm saying that, something must be wrong on the Relay Chain side (on the session keys probably?) because I got the same error Collation wasn't advertised to any validator. Commented Oct 18, 2022 at 12:03
  • Did you try adding more validators to the relaychain. If the validators count too low, it won't assign validators to the parachain.
    – AurevoirXavier
    Commented Oct 18, 2022 at 14:02
  • Yes, I have tried with 3 validators on the Relay Chain but got the same error. Should I need to insert on the Relay validator nodes any kind/type of keys from my Collator? Commented Oct 18, 2022 at 14:20
  • 1
    No, you don't need to do that.
    – AurevoirXavier
    Commented Oct 18, 2022 at 15:02
  • Could you share your relaychain and parachain code?
    – AurevoirXavier
    Commented Oct 18, 2022 at 15:03

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