.ssh directory and private key permissions

The ~/.ssh folder needs 700 and ~/.ssh/id_* (the private key) needs 600.

You can accomplish this with:

mkdir -p ~/.ssh
cp $SSH_KEY_LOCATION ~/.ssh/
chmod 700 ~/.ssh && chmod 600 ~/.ssh/id_*
ls -la ~/.ssh # to verify

Thank you to https://superuser.com/a/215506 who I have literally referenced tens of times for this and keep forgetting.