# Long-Running Sandboxes
source: https://docs.chalk.ai/docs/sandboxes/long-running-sandboxes

## Run a Chalk sandbox for hours or days with a lifetime and a restart policy.

Sandboxes can run for hours or days. Two independent settings govern how long one
lasts: lifetime bounds its total run time, and restart_policy decides whether
Chalk recreates it when its backing instance goes away.

### Setting a lifetime

Omit lifetime to run until you terminate the sandbox yourself. Set it to bound
the run:

| Value       | Effect                                             |
| ----------- | -------------------------------------------------- |
| omitted     | The sandbox runs until it is terminated explicitly |
| `"86400s"`  | The sandbox is terminated 24 hours after it starts |
| `"604800s"` | The sandbox is terminated 7 days after it starts   |

There is no maximum value. lifetime="0s" raises ValueError rather than
meaning "no limit"; omit the argument for that.

When a lifetime expires, Chalk stops the sandbox immediately without draining
in-flight work, and records the result as succeeded. Write anything you need to
keep to a mounted volume before that point.

### Surviving node drains and preemption

A sandbox running for days outlives the node it started on. By default, the
backing instance terminating ends the sandbox. Set restart_policy to have Chalk
recreate it instead:

```
from chalkcompute import Image, RestartPolicy, Sandbox, Volume

Volume("training-checkpoints")  # created if it does not already exist

sandbox = Sandbox(
    image=Image.debian_slim("3.12").pip_install(["torch"]),
    name="multi-day-training",
    cpu="8",
    memory="32Gi",
    volumes=[("training-checkpoints", "/checkpoints")],
    restart_policy=RestartPolicy.ALWAYS,
).run()
```

Leaving restart_policy unset behaves the same as RestartPolicy.NEVER. A
recreated sandbox starts from its image again with an empty ephemeral filesystem,
so write progress to a mounted Volume and have the
workload resume from it on startup.

To start work that runs for hours and check on it later, see
Running work across sessions.