How to fix "SSL_connect ... certificate verify failed" on puppet client

After installing the Puppet client, run:

# puppet agent --test

to connect to the Puppet master. If this error appears:

err: Could not retrieve catalog from remote server:
SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B:
certificate verify failed
warning: Not using cache on failed catalog
err: Could not retrieve catalog; skipping run

the causes are:

1. The client and Puppet master clocks differ significantly. Run ntpdate to update the client’s time, for example: # ntpdate NTPSERVER.COM
2. The client certificate does not match the Puppet master. Regenerate the certificate as follows:
   • Remove the client certificate with: # find /var/lib/puppet -type f -print0 |xargs -0r rm
   • Remove the SSL certificate on the Puppet master with: # puppet cert --clean {node_certname}