まずは現在の鍵の情報を確認。一番上にあるユーザIDがprimaryということ。
$ gpg --list-key XXXXXXXX pub 4096R/XXXXXXXX 2012-02-10 uid AYANOKOUZI, Ryuunosuke <i38w7i3@yahoo.co.jp> uid AYANOKOUZI, Ryuunosuke sub 4096R/YYYYYYYY 2012-02-10
この鍵からprimary ユーザID(uid)を変更。途中でこの鍵のパスフレーズを聞かれる。
$ gpg --edit-key YYYYYYYY
gpg (GnuPG) 1.4.10; Copyright (C) 2008 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Secret key is available.
gpg: checking the trustdb
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0 valid: 2 signed: 0 trust: 0-, 0q, 0n, 0m, 0f, 2u
pub 4096R/XXXXXXXX created: 2012-02-10 expires: never usage: SC
trust: ultimate validity: ultimate
sub 4096R/YYYYYYYY created: 2012-02-10 expires: never usage: E
[ultimate] (1). AYANOKOUZI, Ryuunosuke <i38w7i3@yahoo.co.jp>
[ultimate] (2) AYANOKOUZI, Ryuunosuke
gpg> uid 2
pub 4096R/XXXXXXXX created: 2012-02-10 expires: never usage: SC
trust: ultimate validity: ultimate
sub 4096R/YYYYYYYY created: 2012-02-10 expires: never usage: E
[ultimate] (1). AYANOKOUZI, Ryuunosuke <i38w7i3@yahoo.co.jp>
[ultimate] (2)* AYANOKOUZI, Ryuunosuke
gpg> primary
You need a passphrase to unlock the secret key for
user: "AYANOKOUZI, Ryuunosuke <i38w7i3@yahoo.co.jp>"
4096-bit RSA key, ID XXXXXXXX, created 2012-02-10
pub 4096R/XXXXXXXX created: 2012-02-10 expires: never usage: SC
trust: ultimate validity: ultimate
sub 4096R/YYYYYYYY created: 2012-02-10 expires: never usage: E
[ultimate] (1) AYANOKOUZI, Ryuunosuke <i38w7i3@yahoo.co.jp>
[ultimate] (2)* AYANOKOUZI, Ryuunosuke
gpg> quit
Save changes? (y/N) y
最後に変更内容の確認。uidの順番が変わり、primaryユーザIDが変更されたことがわかる。
$ gpg --list-key XXXXXXXX pub 4096R/XXXXXXXX 2012-02-10 uid AYANOKOUZI, Ryuunosuke uid AYANOKOUZI, Ryuunosuke <i38w7i3@yahoo.co.jp> sub 4096R/YYYYYYYY 2012-02-10