Updating VPS from CentOS 6 to 7. Best line of action with least downtime or possible errors?

[BBM]

I seem to be running into issues with (some) domains not loading on ipv6 and (possibly therefore cause) missing certificates errors.
Of those domains, the website loads fine when viewed from a ipv4-connection, but cause a "This IP is being shared among many domains."-Errorpage on an ipv6-connection.

Last night I tried to go over the ipv6 implementation in DA and noticed I had never actually 'linked' ip4 with ip6. Did that now and expected sites to starts loading again properly but it didn't.

 

[Driesp]

I have done countless DA migrations using rsync with minimal downtime and no data loss ofc. (15 minutes downtime is very possible)
You need a temporary DA (test) license (and temporary IP), when completing the migration move the IP's to the new server.

I would certainly recommend to migrate to rocky (or alma) 8.
I don't know if Rocky 9 is supported by DA already.

If you need help with that, feel free to contact me to do the migration for you.

 

[BBM]

Thanks Dries.
I have 2 VPS servers with DA licenses coupled to them, running at TransIP.
Also have 1 external nameserver which is running DirectSlave.

But I think there are things wrong in the nameserver-records somewhere still. But I find it funny some domains will load over an ip6-connection, and some won't.
If I can't get this sorted in the little time I have I will hire someone to look into my setup and go over everything.