/etc/hosts ::1 line should additionally include 'localhost'

[Jon Grimm]

RFC 6761 6.3 requires that "localhost" (and variations) resolve to 127.0.0.1 or ::1 for IPv4 and IPv6, respectively.

In instances that are installed with D-I (such as the server ISO), I see:

::1 localhost ip6-localhost ip6-loopback

However, in our cloud-images (or derivatives such as LXD), OR in Ubiquity installations, I see:

::1 ip6-localhost ip6-loopback

My examples are from Xenial.

The latter examples, should be fixed up to include localhost for IPv6 per RFC guidance.

Opening bug here per IRC conversation with Steve Langasek.

[Dan Watkins (oddbloke)]

Confirmed in trusty, xenial and zesty. ({t,x,z}-ipv6 are just containers launched from the latest images)

$ lxc exec t-ipv6 cat /etc/hosts
127.0.0.1 localhost

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

$ lxc exec x-ipv6 cat /etc/hosts
127.0.0.1 localhost

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

$ lxc exec z-ipv6 cat /etc/hosts
127.0.0.1 localhost

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

[Dan Watkins (oddbloke)]

The relevant file is http://bazaar.launchpad.net/~ubuntu-core-dev/livecd-rootfs/trunk/view/head:/live-build/ubuntu-cpc/includes.chroot/etc/hosts. This is included wholesale in the images (because it's in includes.chroot).