It seems OP wanted to pass the file name to -k, but this parameter takes the password itself and not a filename:
-k password
The password to derive the keyfrom. This isfor compatibility with previous versions of OpenSSL. Superseded by the -pass argument.
So, as I understand, the password would be not the first line of /etc/ssl/private/etcBackup.key, but the string /etc/ssl/private/etcBackup.key itself. It seems that -kfile /etc/ssl/private/etcBackup.key or -pass file:/etc/ssl/private/etcBackup.key is what OP wanted to use.
It seems OP wanted to pass the file name to
-k
, but this parameter takes the password itself and not a filename:-k password The password to derive the key from. This is for compatibility with previous versions of OpenSSL. Superseded by the -pass argument.
So, as I understand, the password would be not the first line of
/etc/ssl/private/etcBackup.key
, but the string/etc/ssl/private/etcBackup.key
itself. It seems that-kfile /etc/ssl/private/etcBackup.key
or-pass file:/etc/ssl/private/etcBackup.key
is what OP wanted to use.