Posts

Posted on

Adiós self-hosted mail server

As the title suggests, I will be retiring my self-hosted mail server (mx1.staticsafe.ca) soon, most likely by next month.

It has been a lot of fun and an excellent learning experience but I simply cannot devote the time and/or effort into active maintenance of the server.

I am moving all of the mailing lists that I used this server for to the extremely competent folks over at Fastmail.

The retirement will be done in a few stages as follows:

  1. Stage 1 – Personal mailing list subscription move (completed)
  2. Stage 2 – Change of MX, SPF records for staticsafe.ca to Fastmail’s servers and add a wildcard alias there.
  3. Stage 3 – Discontinuation of relay/non-personal services on mx1.staticsafe.ca. One person is using this server as a submission relay for their server. I will be asking them to move to my new MSA only server. Services for caffeine-linux.org will also have to be discontinued.
  4. Stage 4 – Stop all relevant daemons. Postfix, Dovecot, amavisd-new.

My Thanks

A lot of people and/or companies have provided direct and/or indirect support for this learning experience.

  • Linode Library for providing initial inspiration for the current configuration of the server
  • The folks in the Postfix and Dovecot communities. (#postfix, postfix-users, #dovecot, Wietse for the wonderful software)
  • purrdeta for telling me mail servers are a lot of fun

Addendum

I have put my server configuration files on Github if anyone is interested, you can see them here.

Posted on

Ubuntu 14.04 Server and IPv6 Temporary Addresses

So, as we all know Ubuntu 14.04 was released today. I downloaded the server ISO to test in VirtualBox.

Let us see what we have here:

ss@trusty-testing:~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04 LTS"

ss@trusty-testing:~$ ip -6 addr show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
 inet6 2001:470:1d:96b:70bb:7393:2071:faa2/64 scope global temporary dynamic
 valid_lft 597675sec preferred_lft 78675sec

Wait what? Am I going blind or is that an IPv6 temporary address [0] on a supposedly server image?

Investigating further:

ss@trusty-testing:~$ sudo sysctl -a | grep tempaddr
net.ipv6.conf.all.use_tempaddr = 2
net.ipv6.conf.default.use_tempaddr = 2
net.ipv6.conf.eth0.use_tempaddr = 2
net.ipv6.conf.lo.use_tempaddr = 2

What the hell? Not only did they leave temporary addresses turned on, they set the sysctl value at 2 which means that the system will prefer temporary addresses over standard ones for making connections. [1]

I asked around and apparently this is the case on Ubuntu 12.04 server as well.

ss@ubuntu-testing:~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu 12.04.4 LTS"

ss@ubuntu-testing:~$ sudo sysctl -a | grep tempaddr
net.ipv6.conf.all.use_tempaddr = 2
net.ipv6.conf.default.use_tempaddr = 2
net.ipv6.conf.eth0.use_tempaddr = 2
net.ipv6.conf.lo.use_tempaddr = 2

So that is two LTS server releases with IPv6 temporary addresses turned on and set to 2.

Why are temporary addresses bad on a server?

Unpredictability – anything depending on source address validation. Even SLAAC addresses are more predictable because they can be calculated given the MAC address of the NIC.

Ideally, you should be configuring your server’s addresses statically. Leaving temporary addresses turned on on a server image is just a bad default.

References:
[0] – https://tools.ietf.org/html/rfc4941
[1] – http://ipv6int.net/systems/linux-ipv6.html#privacy

Posted on

The Path to DNS Independence (Part 2)

To quote from Wikipedia:

An authoritative name server is a name server that gives answers that have been configured by an original source, for example, the domain administrator or by dynamic DNS methods, in contrast to answers that were obtained via a regular DNS query to another name server. An authoritative-only name server only returns answers to queries about domain names that have been specifically configured by the administrator.

Continuing on from my theme of DNS independence, I’d like to explore the advantages and disadvantages of hosting your own authoritative name servers.

Let us take a look at my own setup for authoritative name servers.

Continue reading “The Path to DNS Independence (Part 2)”