What is the least painful way to migrate state of resources from one project (i.e., move a module invocation) to another, particularly when using remote state storage? While refactoring is relatively straightforward within the same state file (i.e., take this resource and move it to a submodule or vice-versa), I don't see an alternative to JSON surgery for refactoring into different state files, particularly if we use remote (S3) state (i.e., take this submodule and move it to another project).
The least painful way I’ve found is to pull both remote states local, move the modules/resources between the two, then push back up. Also remember, if you’re moving a module, don’t move the individual resources; move the whole module.
For example:
cd dirA
terraform state pull > ../dirA.tfstate
cd ../dirB
terraform state pull > ../dirB.tfstate
terraform state mv -state=../dirA.tfstate -state-out=../dirB.tfstate module.foo module.foo
terraform state push ../dirB.tfstate
# verify state was moved
terraform state list | grep foo
cd ../dirA
terraform state push ../dirA.tfstate
Unfortunately, the terraform state mv command doesn’t support specifying two remote backends, so this is the easiest way I’ve found to move state between multiple remotes.