I am working on a test in [metallb-operator](https://github.com/charmed-kubernetes/metallb-operator) and was trying to build the two charms for that in parallel. It worked fine for me locally, but on the GitHub runner (a fresh VM, with a fresh install of both lxd and charmcraft on the default channel / track), I ran into a few errors that appear to be due to race conditions in setting up LXD for the builder. The first one I [ran into](https://github.com/charmed-kubernetes/metallb-operator/pull/18/checks?check_run_id=3693265761#step:6:58) (NB: these build log links will eventually expire) was: ``` Packing charm 'metallb-speaker_ubuntu-20.04-amd64.charm'... charmcraft internal error! LXDError: Failed to add remote 'craft-com.ubuntu.cloud-buildd'. * Command that failed: 'lxc remote add craft-com.ubuntu.cloud-buildd https://cloud-images.ubuntu.com/buildd/releases --protocol=simplestreams' * Command exit code: 1 * Command standard error output: b'Error: Remote craft-com.ubuntu.cloud-buildd exists as <https://cloud-images.ubuntu.com/buildd/releases>\n' (full execution logs in /home/runner/snap/charmcraft/common/charmcraft-log-osa2otki) ``` I tried working around that by running that `lxc` command manually earlier in the Workflow, but then I [ran into](https://github.com/charmed-kubernetes/metallb-operator/pull/18/checks?check_run_id=3700739113#step:7:58): ``` Packing charm 'metallb-controller_ubuntu-20.04-amd64.charm'... charmcraft internal error! LXDError: Failed to create project 'charmcraft'. * Command that failed: 'lxc --project charmcraft project create local:charmcraft' * Command exit code: 1 * Command standard error output: b'Error: Failed creating project "charmcraft": Failed adding database record: This project already exists\n' (full execution logs in /home/runner/snap/charmcraft/common/charmcraft-log-4l5wgu0x) ``` Once again, I added the `lxc` command to the Workflow before the build, and then I [ran into](https://github.com/charmed-kubernetes/metallb-operator/pull/18/checks?check_run_id=3700929568#step:7:59): ``` Packing charm 'metallb-controller_ubuntu-20.04-amd64.charm'... charmcraft internal error! LXDError: Failed to launch instance 'charmcraft-metallb-controller-1058053-0-0-amd64'. * Command that failed: "lxc --project charmcraft launch craft-com.ubuntu.cloud-buildd:20.04 local:charmcraft-metallb-controller-1058053-0-0-amd64 --config 'raw.idmap=both 1001 0' --config security.syscalls.intercept.mknod=true" * Command exit code: 1 * Command output: b'Creating charmcraft-metallb-controller-1058053-0-0-amd64\n' * Command standard error output: b'Error: Failed instance creation: Failed creating instance record: Failed initialising instance: Invalid devices: Failed detecting root disk device: No root device could be found\n' (full execution logs in /home/runner/snap/charmcraft/common/charmcraft-log-jsos__q1) ``` That one has me stumped so I ended up just de-parallelizing the builds and that works, but it is slower and the errors were confusing and not immediately obvious that they were due to the concurrent build conflict.