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EC2 cloud-init overwrites 127.0.1.1 in /etc/hosts on every reboot #2221

Closed ubuntu-server-builder closed 1 year ago

ubuntu-server-builder commented 1 year ago

This bug was originally filed in Launchpad as LP: #890501

Launchpad details 
affected_projects = ['cloud-init (Ubuntu)']
assignee = smoser
assignee_name = Scott Moser
date_closed = 2012-04-11T04:09:34.951522+00:00
date_created = 2011-11-15T01:13:27.417628+00:00
date_fix_committed = 2011-12-20T03:51:12.684320+00:00
date_fix_released = 2012-04-11T04:09:34.951522+00:00
id = 890501
importance = medium
is_complete = True
lp_url = https://bugs.launchpad.net/cloud-init/+bug/890501
milestone = None
owner = smoser
owner_name = Scott Moser
private = False
status = fix_released
submitter = esh
submitter_name = Eric Hammond
tags = ['apport-bug', 'ec2-images', 'i386', 'oneiric']
duplicates = []

Launchpad user Eric Hammond(esh) wrote on 2011-11-15T01:13:27.417628+00:00

When running an EC2 instance of Ubuntu 11.10 Oneiric, cloud-init sets up /etc/hosts with a default value for 127.0.1.1 looking something like:

    127.0.1.1 ip-10-202-61-233.ec2.internal ip-10-202-61-233

I edit /etc/hosts to change this value to something that makes more sense to my internal software (e.g., Apache). For example:

    127.0.1.1 myhost.example.com myhost

BUG: Whenever I reboot the EC2 instance, cloud-init overwrites my important settings of this value back to the old default. This breaks the startup of my applications on the server as they expect to be able to resolve the names I want set in the /etc/hosts file. My web server never comes up after a simple reboot.

Once the user edits the value for 127.0.1.1 in the /etc/hosts file, it should never be overwritten. Not on a reboot. Not on a stop/start (which assigns new IP addresses). Not even when an AMI is built out of this instance and a new instance is run.

The user changed that value to something they cared about with reasons we can't assume to trump. It should be left alone.

If /etc/hosts does not exist or if 127.0.1.1 is still the same value that cloud-init last set it to, then it might be acceptable to overwrite it with a value based on a change in the private IP address, HOWEVER, this might still break the application if software configured itself using the old value.

Either never change the value if it exists, or store elsewhere the value that was initially set and only change it if it is still the same.

See also bug #371936 where a similar bug was fixed back in 2009. Figure out if there is some reason that this part of the system is fragile and prone to breaking.

ProblemType: Bug DistroRelease: Ubuntu 11.10 Package: cloud-init 0.6.1-0ubuntu22 ProcVersionSignature: User Name 3.0.0-12.20-virtual 3.0.4 Uname: Linux 3.0.0-12-virtual i686 ApportVersion: 1.23-0ubuntu3 Architecture: i386 Date: Tue Nov 15 00:17:46 2011 Ec2AMI: ami-a7f539ce Ec2AMIManifest: (unknown) Ec2AvailabilityZone: us-east-1d Ec2InstanceType: t1.micro Ec2Kernel: aki-805ea7e9 Ec2Ramdisk: unavailable PackageArchitecture: all ProcEnviron:  LANG=en_US.UTF-8  SHELL=/bin/bash SourcePackage: cloud-init UpgradeStatus: No upgrade log present (probably fresh install)

related bugs:

ubuntu-server-builder commented 1 year ago

Launchpad user Eric Hammond(esh) wrote on 2011-11-15T01:13:27.417628+00:00

Launchpad attachments: Dependencies.txt

ubuntu-server-builder commented 1 year ago

Launchpad user Scott Moser(smoser) wrote on 2011-11-15T03:28:33.222448+00:00

Thanks for the bug report. I believe that you should be able to simply add an entry above the one labeled 'cloud-init'

$ grep -v :: /etc/hosts 127.0.0.1 localhost 127.0.1.2 superman.brickies.net superman

The following lines are desirable for IPv6 capable hosts

Added by cloud-init

127.0.1.1 ip-10-212-231-182.ec2.internal ip-10-212-231-182 $ cat /etc/hostname superman $ hostname -f superman.brickies.net $ ping -c 1 superman.brickies.net -q PING superman.brickies.net (127.0.1.2) 56(84) bytes of data.

--- superman.brickies.net ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.028/0.028/0.028/0.000 ms

ubuntu-server-builder commented 1 year ago

Launchpad user Eric Hammond(esh) wrote on 2011-11-15T05:34:36.875647+00:00

Scott: Learn something new every day. I will give this a try.

ubuntu-server-builder commented 1 year ago

Launchpad user Eric Hammond(esh) wrote on 2011-11-15T05:57:16.198734+00:00

Scott: Your suggested approach works for me even though I can't find any documentation on how this is supposed to work. Everything I read says that 127.0.1.1 should be the canonical hostname of the instance. Do you happen to have any pointers to the information you are alluding to with IPv6 and 127.0.1.2?

ubuntu-server-builder commented 1 year ago

Launchpad user Scott Moser(smoser) wrote on 2011-11-15T13:23:42+00:00

On Tue, 15 Nov 2011, Eric Hammond wrote:

Scott: Your suggested approach works for me even though I can't find any documentation on how this is supposed to work. Everything I read says that 127.0.1.1 should be the canonical hostname of the instance. Do you happen to have any pointers to the information you are alluding to with IPv6 and 127.0.1.2?

No. I actually tried just adding a 127.0.1.1 at the top, and cloud-init still found it (i was hoping that it would only update the one preceeded by it's comment, which would have been nicer). I tried that, it didn't work. I don't think this should be "invalid" as I do think we've made things a bit worse. We were addressing the issue that we saw on openstack where the ec2metadata's local-hostname did not have a domain portion (bug 854614).

Some other fallout of this change has been in services that try to bind to the response to hostname -f. The service will then end up binding to localhost only and not be available on a real address. Mark Mimms has raised this issue, but I'm not certain which services in particular, and I don't think that is a great solution itself, and those services would have issues with the mechanism that you're using above for /etc/hosts, but previously we were not writing a fqdn to /etc/hosts, which would allow a dns-lookup to get the local-ipv4 address.

I'll talk with some of the people on the foundations team and see if we can't come up with a final solution for this. I really should have done some more research before putting this in. Hopefully we can get it right for 12.04, and possibly SRU for 11.10.

ubuntu-server-builder commented 1 year ago

Launchpad user Scott Moser(smoser) wrote on 2011-12-20T03:51:11.574144+00:00

This is fix-commited in cloud-init in revision 491 (http://bazaar.launchpad.net/~cloud-init-dev/cloud-init/trunk/revision/491). See the commit message there for more information.

ubuntu-server-builder commented 1 year ago

Launchpad user Launchpad Janitor(janitor) wrote on 2011-12-22T09:10:13.291010+00:00

This bug was fixed in the package cloud-init - 0.6.3~bzr497-0ubuntu1

cloud-init (0.6.3~bzr497-0ubuntu1) precise; urgency=low