Fixing rust cross "Permission denied (os error 13)"

Today I spent 1 hour trying to solve this error:

error: failed to open: /target/debug/.cargo-lock

Caused by:
  Permission denied (os error 13)

after trying to run cross build --target=x86_64-unknown-linux-musl

Putting my detective hat on, we can guess that it has to do something with file permissions, so lets just 777 that bad boy and get it over and done with? No!

This problem happens because the user within the docker container that cross runs has the permissions uid=0, gid=0, and our folder is 1000:1000!

After digging into the cross changelog, we can find a pull request that can help us out:

CROSS_CONTAINER_UID=0 CROSS_CONTAINER_GID=0 cross build --target=x86_64-unknown-linux-musl

or more simply:

sudo chown -R 0:0 target/

Sometimes it’s good to know how file permissions work in linux.