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adam
Asked: 2017-10-01 15:28:48 +0800 CST

Google Cloud Compute keeps changing my /etc/hosts file after restart

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I have been playing around with 3 google cloud compute instances using webmin/virtualmin (web hosting and email), Vestacp (hosting only), and ISPconfig (hosting only) control panels.

The ISPConfig instance has a static external ip address, however the other 2 at this stage are dhcp.

All 3 instances are using a dynamically assigned internal ip addresses, although i have not yet seen any of those ip addresses change in 6 months of testing and restarting and deleting and re-deploying. Whenever i delete an instance, the same internal ip sequence is used (ie whatever is the next lowest unassigned available number is re-added as internal ip address).

I am having some problems with forcing google cloud to bloodywell stop changing my hostname -f configuration in my /etc/hosts file.

It should read

127.0.0.1 localhost.localdomain localhost
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
10.x.x.x server1.foo.com.au server1

(where x is my internal ip address, "foo" is my domain name)

However, on any 3 of my instances, as soon as i reboot the instance, google cloud adds its own code back in again on next restart. ie by default google cloud keeps changing the file to read the same 2 "# added by Google" lines as shown below

127.0.0.1 localhost.localdomain localhost
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
10.x.x.x server1.foo.com.au server1
10.x.x.x server1.c.bar.internal server1 # Added by Google
169.254.169.254 metadata.google.internal # Added by Google

(where x is my internal ip address, "foo" is my actual domain name, and "bar" is my google cloud project ID)

This is really causing me problems and i have no idea on which is the best way around it.

-Do i do it from within google cloud DNS API? -setup a static internal ip address in google cloud network settings? -setup a script that continues to check for a change to this file and immediately replace any changes google cloud attempts to make? -or do i need to change the metadata information on the last line of my hosts file so it does not have "...metadata.google.internal # Added by Google" line?

At present option 1 above is not working. As soon as i enable the DNS API then try to enter it i get a "failed to load" error from within my google cloud console. This is a flaming pain in the ass!!! (i have sent a support request to google...who knows how long it will take for an answer)

hostname

2 Answers

  1. Best Answer

    Ghetto option that may not work: sudo chattr +i /etc/hosts

    Do man chattr for details, but this makes the file "(i)mmutable", which means even root can't change it (unless root does chattr -i /etc/hosts first, of course).

    As above, you can undo this with sudo chattr -i /etc/hosts

    Why it happens: I'm guessing you have a process (perhaps dhcpcd or something) that obtains host information from some source, and then updates various files including /etc/hosts (and probably /etc/resolv.conf, which was why I ended up using chattr). The right way to fix things is figure out what process is doing this and configure it do the right thing. You could also do "cp /etc/hosts.correct /etc/hosts" after the process is done mangling your file, but you have to do this late enough in the bootup process that it happens after the process is done mangling.

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  2. On GCP/Ubuntu (Xenial at least), /etc/hosts is manipulated and hostname is being via a DHCP (client) exit hook:

    /etc/dhcp/dhclient-exit-hooks.d/google_set_hostname

    which is installed by the package gce-compute-image-packages which is default on GCE images.

    You can hack it (exit 0) or remove it; make sure to take care when the package is upgraded, it can overwrite the hook again depending on apt/dpkg settings.

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