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Deploy a Program

Developers can deploy on-chain programs (often called smart contracts elsewhere) with the Velas tools.

To learn about developing and executing programs on Velas, start with the overview and then dig into the details of on-chain programs.

To deploy a program, use the Velas tools to interact with the on-chain loader to:

  • Initialize a program account
  • Upload the program's shared object to the program account's data buffer
  • Verify the uploaded program
  • Finalize the program by marking the program account executable.
  • Once deployed, anyone can execute the program by sending transactions that reference it to the cluster.


Deploy a program

To deploy a program, you will need the location of the program's shared object (the program binary .so)

velas program deploy <PROGRAM_FILEPATH>

Successful deployment will return the program id of the deployed program, for example:

Program Id: 3KS2k14CmtnuVv2fvYcvdrNgC94Y11WETBpMUGgXyWZL

Specify the keypair in the deploy command to deploy to a specific program id:

velas program deploy --program-id <KEYPAIR_FILEPATH> <PROGRAM_FILEPATH>

If the program id is not specified on the command line the tools will first look for a keypair file matching the <PROGRAM_FILEPATH>, or internally generate a new keypair.

A matching program keypair file is in the same directory as the program's shared object, and named <PROGRAM_NAME>-keypair.json. Matching program keypairs are generated automatically by the program build tools:


Showing a program account

To get information about a deployed program:

velas program show <ACCOUNT_ADDRESS>

An example output looks like:

Program Id: 3KS2k14CmtnuVv2fvYcvdrNgC94Y11WETBpMUGgXyWZL
Owner: BPFLoaderUpgradeab1e11111111111111111111111
ProgramData Address: EHsACWBhgmw8iq5dmUZzTA1esRqcTognhKNHUkPi4q4g
Authority: FwoGJNUaJN2zfVEex9BB11Dqb3NJKy3e9oY3KTh9XzCU
Last Deployed In Slot: 63890568
Data Length: 5216 (0x1460) bytes
  • Program Id is the address that can be referenced in an instruction's program_id field when invoking a program.
  • Owner: The loader this program was deployed with.
  • ProgramData Address is the account associated with the program account that holds the program's data (shared object).
  • Authority is the program's upgrade authority.
  • Last Deployed In Slot is the slot in which the program was last deployed.
  • Data Length is the size of the space reserved for deployments. The actual space used by the currently deployed program may be less.

Redeploy a program

A program can be redeployed to the same address to facilitate rapid development, bug fixes, or upgrades. Matching keypair files are generated once so that redeployments will be to the same program address.

The command looks the same as the deployment command:

velas program deploy <PROGRAM_FILEPATH>

By default, programs are deployed to accounts that are twice the size of the original deployment. Doing so leaves room for program growth in future redeployments. But, if the initially deployed program is very small (like a simple helloworld program) and then later grows substantially, the redeployment may fail. To avoid this, specify a max_len that is at least the size (in bytes) that the program is expected to become (plus some wiggle room).

velas program deploy --max-len 200000 <PROGRAM_FILEPATH>

Note that program accounts are required to be rent-exempt, and the max-len is fixed after initial deployment, so any VLX in the program accounts is locked up permanently.

Resuming a failed deploy

If program deployment fails, there will be a hanging intermediate buffer account that contains a non-zero balance. In order to recoup that balance you may resume a failed deployment by providing the same intermediate buffer to a new call to deploy.

Deployment failures will print an error message specifying the seed phrase needed to recover the generated intermediate buffer's keypair:

Recover the intermediate account's ephemeral keypair file with
`velas-keygen recover` and the following 12-word seed phrase:
valley flat great hockey share token excess clever benefit traffic avocado athlete
To resume a deploy, pass the recovered keypair as
the [PROGRAM_ADDRESS_SIGNER] argument to `velas deploy` or
as the [BUFFER_SIGNER] to `velas program deploy` or `velas write-buffer'.
Or to recover the account's lamports, pass it as the
[BUFFER_ACCOUNT_ADDRESS] argument to `velas program drain`.

To recover the keypair:

velas-keygen recover -o <KEYPAIR_PATH>

When asked, enter the 12-word seed phrase.

Then issue a new deploy command and specify the buffer:

velas program deploy --buffer <KEYPAIR_PATH> <PROGRAM_FILEPATH>

Closing buffer accounts and reclaiming their lamports

If deployment fails there will be a left over buffer account that holds lamports. The buffer account can either be used to resume a deploy or closed. When closed, the full balance of the buffer account will be transferred to the recipient's account.

The buffer account's authority must be present to close a buffer account, to list all the open buffer accounts that match the default authority:

velas program show --buffers

To specify a different authority:

velas program show --buffers --buffer-authority <AURTHORITY_ADRESS>

To close a single account:

velas program close <BUFFER_ADDRESS>

To close a single account and specify a different authority than the default:

velas program close <BUFFER_ADDRESS> --buffer-authority <KEYPAIR_FILEPATH>

To close a single account and specify a different recipient than the default:

velas program close <BUFFER_ADDRESS> --recipient <RECIPIENT_ADDRESS>

To close all the buffer accounts associated with the current authority:

velas program close --buffers

To show all buffer accounts regardless of the authority

velas program show --buffers --all

Set a program's upgrade authority

The program's upgrade authority must to be present to deploy a program. If no authority is specified during program deployment, the default keypair is used as the authority. This is why redeploying a program in the steps above didn't require an authority to be explicitly specified.

The authority can be specified during deployment:

velas program deploy --upgrade-authority <UPGRADE_AUTHORITY_SIGNER> <PROGRAM_FILEPATH>

Or after deployment and using the default keypair as the current authority:

velas program set-upgrade-authority <PROGRAM_ADDRESS> --new-upgrade-authority <NEW_UPGRADE_AUTHORITY>

Or after deployment and specifying the current authority:

velas program set-upgrade-authority <PROGRAM_ADDRESS> --upgrade-authority <UPGRADE_AUTHORITY_SIGNER> --new-upgrade-authority <NEW_UPGRADE_AUTHORITY>

Immutable programs

A program can be marked immutable, which prevents all further redeployments, by specifying the --final flag during deployment:

velas program deploy <PROGRAM_FILEPATH> --final

Or anytime after:

velas program set-upgrade-authority <PROGRAM_ADDRESS> --final

velas program deploy ... utilizes Velas' upgradeable loader, but there is another way to deploy immutable programs using the original on-chain loader:

velas deploy <PROGRAM_FILEPATH>

Programs deployed with velas deploy ... are not redeployable and are not compatible with the velas program ... commands.

Dumping a program to a file

The deployed program may be dumped back to a local file:


The dumped file will be in the same as what was deployed, so in the case of a shared object, the dumped file will be a fully functional shared object. Note that the dump command dumps the entire data space, which means the output file will have trailing zeros after the shared object's data up to max_len. Sometimes it is useful to dump and compare a program to ensure it matches a known program binary. The original program file can be zero-extended, hashed, and compared to the hash of the dumped file.

$ velas dump <ACCOUNT_ADDRESS>
$ cp
$ truncate -r
$ sha256sum

Using an intermediary Buffer account

Instead of deploying directly to the program account, the program can be written to an intermediary buffer account. Intermediary accounts can useful for things like multi-entity governed programs where the governing members fist verify the intermediary buffer contents and then vote to allow an upgrade using it.

velas program write-buffer <PROGRAM_FILEPATH>

Buffer accounts support authorities like program accounts:

velas program set-buffer-authority <BUFFER_ADDRESS> --new-upgrade-authority <NEW_UPGRADE_AUTHORITY>

One exception is that buffer accounts cannot be marked immutable like program accounts can, so they don't support --final.

The buffer account, once entirely written, can be passed to deploy to deploy the program:

velas program deploy --program-id <PROGRAM_ADDRESS> --buffer <BUFFER_ADDRESS>

Note, the buffer's authority must match the program's upgrade authority.

Buffers also support show and dump just like programs do.