### Bug Description The `Base` class can accept an optional [`compatibility_tag`](https://github.com/canonical/craft-providers/blob/03704c107b3d88132a33453302c79da1dc9619c5/craft_providers/base.py#L107). If a `compatibility_tag` is not provided and craft-providers launches LXD instances for 2 different projects, LXD will fail because the two base instances have identical names. Source: https://github.com/canonical/craft-application/issues/139 ### Quick fix craft-providers should log a warning if a compatibility tag is not provided: ``` Warning: Compatibilty tag not provided. This may cause a name collision when launching LXD instances. ``` ### Long term fix As part of a major release, the `compatibility_tag` should be easier to use. It should be required and prepended to the base's compatibility tag. This simply the usage from: ```python from craft_providers import bases base = bases.BuilddBase(compatibility_tag=f"testcraft-{bases.BuildBase.compatibility_tag}", ...) ``` to: ```python from craft_providers import bases base = bases.BuilddBase(compatibility_tag="testcraft", ...) ``` ### To Reproduce ```python #! /usr/bin/env python3 from pathlib import Path import logging from craft_providers import bases, lxd logging.basicConfig(level="DEBUG") provider_a = lxd.LXDProvider(lxd_project="project1") provider_a.ensure_provider_is_available() alias = bases.BuilddBaseAlias.JAMMY my_base = bases.BuilddBase(alias=alias) with provider_a.launched_environment( project_name = "hello-world", project_path = Path().absolute(), base_configuration=my_base, build_base=alias.value, instance_name = "test-instance", ) as instance: instance.execute_run(["ls"]) provider_b = lxd.LXDProvider(lxd_project="project2") provider_b.ensure_provider_is_available() alias = bases.BuilddBaseAlias.JAMMY my_base = bases.BuilddBase(alias=alias) with provider_b.launched_environment( project_name = "hello-world", project_path = Path().absolute(), base_configuration=my_base, build_base=alias.value, instance_name = "test-instance", ) as instance: instance.execute_run(["ls"]) ``` ### part yaml _No response_ ### Relevant log output ```shell * Command standard error output: b'Error: Failed start validation for device "eth0": Instance DNS name "base-instance-buildd-base-v3-craft-comub-523148486bd0c6cc722c" already used on network\nTry `lxc info --show-log local:base-instance-buildd-base-v3-craft-comub-523148486bd0c6cc722c` for more info\n' ```