I expected gpgconf --homedir $x --kill keyboxd to terminate a running keyboxd daemon.
This does not appear to work with 2.4.7:
0 dkg@bob:~$ mkdir -m 0700 /tmp/gg 0 dkg@bob:~$ echo use-keyboxd > /tmp/gg/common.conf 0 dkg@bob:~$ gpg --homedir /tmp/gg --list-keys gpg: /tmp/gg/trustdb.gpg: trustdb created 0 dkg@bob:~$ find /tmp/gg/ /tmp/gg/ /tmp/gg/public-keys.d /tmp/gg/public-keys.d/pubring.db /tmp/gg/public-keys.d/pubring.db.lock /tmp/gg/public-keys.d/.#lk0x00007f1fc8002290.bob.1154303 /tmp/gg/trustdb.gpg /tmp/gg/common.conf 0 dkg@bob:~$ lsof /tmp/gg/public-keys.d/* COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME keyboxd 1154303 dkg 7u REG 0,34 65536 984130 /tmp/gg/public-keys.d/pubring.db 1 dkg@bob:~$ gpgconf --homedir /tmp/gg --kill keyboxd 0 dkg@bob:~$ lsof /tmp/gg/public-keys.d/* COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME keyboxd 1154303 dkg 7u REG 0,34 65536 984130 /tmp/gg/public-keys.d/pubring.db 1 dkg@bob:~$