The process is "clamscan", not "clamd".
- clamd is a daemon and amavisd talks to it via a unix socket. It loads files under /var/lib/clamav/ when it starts, then scan emails with loaded files.
- clamscan is a one-shot command, it loads all files under /var/lib/clamav/ each time it launches, so it takes long time and causes high CPU usage.
Try this:
- stop amavisd and clamd@amavisd services first
- wait for clamscan to finish (or kill them if you don't want to wait)
- start clamd@amavisd. Make sure clamd socket path exists.
- start amavisd service.
btw, how much RAM does this server have?