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6

ssh'ing to a VM is no different than ssh'ing to any other system on the network. Log into one of the VM's, and type: ssh remote_username@remote_host remote_host should be the hostname of the machine you want to connect to. You could even use simply the ip of the host you want to connect to. This guide is pretty basic if you want to get some more info ...


4

DHCP works via a multicast request for an IP address. Which gets an IP address from the first DHCP server to respond. There is no way that I know of to force the client to get a DHCP address from a specific server. In fact, running two DHCP servers that are not aware of each other is asking for the type of trouble you are running into. You need to get the ...


3

The first answer from jornane is correct so far as it goes, however I do not believe it addresses what the OP is really trying to get at - which is how best to handle migration of email and accounts, rather than how to handle DNS. Ordinarily there are many ways to handle this task, but because we are dealing with only one server which will be going through ...


2

There are other good answers to this, but they're fairly theoretical. I thought it might be useful for you to know that I've done this, on a number of occasions, and it's fine, but on CentOS servers using dovecot and sendmail, and I use mbox as a storage format. I know you're using postfix and Maildir, and I'm sorry I can't shed specific light on that; I ...


2

Your hardware clock should be storing UTC time, but you forgot to use the -u option to tell hwclock this. For example, hwclock -ru Resetting the date and then running hwclock -su will resolve the problem.


2

Short answer is yes. To be absolutely accurate the final command would probably be sendmail -bd -q15m. Assuming a dist based on init scripts you can always have a look at the scripts in /etc/init.d to see what can be set in the sysconfig file and how the commands are built up.


2

A better way now is to use the Match keyword: Match Host myworkstation PermitRootLogin yes or Match Address 192.168.1.100 PermitRootLogin yes That way, you can leave PermitRootLogin set to 'no', but you can still log in as root from your workstation. This can also be used, for example, to allow root to rsync data between two hosts.


2

CentOS 6 default installation sets up Postfix listening on localhost. You can disable it with chkconfig or uninstall it with yum, but you need to provide a replacement as the system needs a way to send mail to an administrator in various situations.


2

The address 2001:41d0:2:XXXX::/64 has an all-zero host part. Try assigning a proper address, eg. 2001:41d0:2:XXXX::YYYY/64. Before you try pinging a host on the Internet like ipv6.google.com, check if you can ping the default gateway by its numeric address 2001:41d0:2:xxff:ff:ff:ff:ff. Also check if XXXX == xxff in the above addresses. Otherwise your ...


2

TL;DR E-mail servers will keep messages in their queue a few days if they can't be delivered. Normally during a migration, you'd have to change DNS records, but since you're staying with the same server (same IP) there's no need for that. You can simply shutdown the server, install the new one, and you're good to go. The only important thing is that you ...


1

You've done this: # Drops all incoming TCP that's not directed to these ports, # Preventing also answers for locally initiated connections! ip6tables -A INPUT -p tcp -m multiport ! --dports 21,22,80,443 -j DROP # Drops all incoming UDP that's not directed to these ports, # Preventing also answers for locally initiated connections! ip6tables -A INPUT -p udp ...


1

As Tilman Schmidt already pointed out, you have an all-zero host part. However, I also had trouble enabling IPv6 in an LXC container. This worked for me on CentOS 7: In /etc/sysconfig/network-scripts/ifcfg-eth0, add: IPV6INIT=yes IPV6_AUTOCONF=yes IPV6_DEFROUTE=yes IPV6_PEERDNS=yes IPV6_PEERROUTES=yes IPV6_FAILURE_FATAL=yes ...


1

Building from source is quite straightforward. Digital Ocean has a nice guide on building Git from source on CentOS 7. Place the resulting binary in /usr/local/bin/ on your CentOS 7 system (which, by default, is included in your $PATH) and you're good to go. Of course you would prefer packages/using the repo, however given your situation I would not ...



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