 -  openssl version > /dev/null 2>&1 || _exiterr "This script requires an openssl binary."
 +  ${OPENSSL} version > /dev/null 2>&1 || _exiterr "This script requires an openssl binary."
    _sed "" < /dev/null > /dev/null 2>&1 || _exiterr "This script requires sed with support for extended (modern) regular expressions."
-   grep -V > /dev/null 2>&1 || _exiterr "This script requires grep."
+   command -v grep > /dev/null 2>&1 || _exiterr "This script requires grep."
    mktemp -u -t XXXXXX > /dev/null 2>&1 || _exiterr "This script requires mktemp."
-@@ -67,7 +74,7 @@
+@@ -65,7 +72,7 @@
    WELLKNOWN=
    PRIVATE_KEY_RENEW="no"
    KEY_ALGO=rsa

         printf "(Longer than %d days). " "${RENEW_DAYS}"
         if [[ "${force_renew}" = "yes" ]]; then
           echo "Ignoring because renew was forced!"
@@ -654,7 +661,7 @@
 
   echo "Revoking ${cert}"
 

   rm -f "${tmp_openssl_cnf}"
 
   crt_path="${BASEDIR}/certs/${domain}/cert-${timestamp}.pem"
@@ -526,9 +533,9 @@
   # Create fullchain.pem
   echo " + Creating fullchain.pem..."
   cat "${crt_path}" > "${BASEDIR}/certs/${domain}/fullchain-${timestamp}.pem"
