gpg --list-secret-keys --keyid-format LONG
Example output:
pub 4096R/ABC12345 2020-01-01 [expires: 2025-12-31] uid Your Name <user@example.com> sub 4096R/DEF67890 2020-01-01 [expires: 2025-12-31]
Remember the ID of your key (second column, after the slash, e.g. “ABC12345”). If you have a “sub” entry, you can ignore it.
Run this command to export your key:
gpg --export-secret-keys YOUR_ID_HERE > private.key
Run this command to import your key:
gpg --import private.key