Google Compute Engine: how to set hostname permanently?

Question

How do I set the hostname of an instance in GCE permanently? I can set it via hostname,but after reboot it is gone again.

I tried to feed in metadata (hostname:f.q.d.n), but that did not do the job. But it should work via metadata (https://github.com/GoogleCloudPlatform/compute-image-packages/tree/master/google-startup-scripts).

Anybody an idea?

score 20 · Accepted Answer · answered Aug 28 '14 at 15:41

20

The most simple way to achieve it is creating a simple script and that's what I have done.

I have stored the hostname in the instance metadata and then I retrieve it every time the system restarts in order to set the hostname using a cron job.

$ gcloud compute instances add-metadata <instance> --metadata hostname=<new_hostname> 
$ sudo crontab -e

And this is the line that must be appended in crontab

@reboot hostname $(curl --silent "http://metadata.google.internal/computeMetadata/v1/instance/attributes/hostname" -H "Metadata-Flavor: Google")

After these steps, every time you restart your instance it will have the hostname <new_hostname>. You can check it in the prompt or with the command: hostname

answered Aug 28 '14 at 15:41

Adrián

2,876
17
22

Appears to be a viable solution. But I settled with the advice not to change the hostname, because it is not necessary. All outside appearing hostnames can/should be set in the respective applications. – Michael Schmidt Aug 29 '14 at 13:42
2

Nice solution @Adrián, thanks! But doesn't work for me. It seems that google sets the hostname after the startup pf the cron daemon... – Andrei Boyanov Oct 08 '15 at 07:27
1

Inspired by this solution, I wrote a patch that preserves your hostname from overwriting from Google. http://stackoverflow.com/a/38344684/1325832 – tacke Jul 13 '16 at 07:12
2

This did not work for me - another solution here did: https://stackoverflow.com/a/53607475/8177355 – Matthew Rideout Feb 02 '19 at 21:19

score 14 · Answer 2 · edited Feb 05 '23 at 15:34

14

You need to remove the file /etc/dhcp/dhclient.d/google_hostname.sh

rm -rf /etc/dhcp/dhclient.d/google_hostname.sh
rm -rf /etc/dhcp/dhclient-exit-hooks.d/google_set_hostname

It's worth noting that this script is needed in order to run gcloud beta compute instances create with the --hostname flag. If this script is absent on a base image, new VM instances will preserve the source hostname/FQDN!

edited Feb 05 '23 at 15:34

N W

47
7

answered Jan 10 '18 at 15:43

Sergey Safarov

436
4
11

This simply fix the problem – rafalefighter Nov 16 '18 at 03:06
Exactly what I was looking for. – Samit Jul 14 '19 at 12:42

score 12 · Answer 3 · answered May 26 '15 at 21:28

12

Edit rc.local

sudo nano /etc/rc.local

Add your line under the rest:

hostname *your.hostname.com*

Make sure to run the following after for the script to be executed

chmod +x /etc/rc.d/rc.local

Reboot, and profit.

answered May 26 '15 at 21:28

Oorweeg

121
1
3

This does not work - the hostname is not resolvable outside of that one machine. – kliew Nov 27 '16 at 21:33
Setting the hostname is intended to be local only; changing DNS is a different question. – Dan Pritts Feb 05 '19 at 16:28

score 5 · Answer 4 · edited May 23 '17 at 12:24

5

That isn't possible. Please take a look at this answer. The following article explains that the "hostname" is part of the default metadata entries and it is not possible to manually edit any of the default metadata pairs. As such, you would need to use a script or something else to change the hostname every time the system restarts, otherwise it will automatically get re-synced with the metadata server on every reboot.

You can find information on startup scripts for GCE in this article. You can visit this one for info on how to apply the script to an instance.

edited May 23 '17 at 12:24

Community

1
1

answered Aug 20 '14 at 15:51

Boyan

709
4
8

I don't mind to use a script to set the hostname at boot time. BUt don't know, how to fill in metadata to which script. – Michael Schmidt Aug 20 '14 at 17:26
You can visit https://developers.google.com/compute/docs/howtos/startupscript for the article on 'startup scripts'. I will also update my answer to include this information. This way it will run every time at startup. When you're specifying which script to run, you can use local file, a file from Google Cloud Storage or a URL. You can visit https://developers.google.com/compute/docs/metadata#updatinginstancemetadata for information on how to update the metadata for your instance in order to apply a startup script. – Boyan Aug 20 '14 at 18:31

score 4 · Answer 5 · answered Dec 23 '15 at 16:39

You can also create a simple startup-script to do the jobs:

$ gcloud compute instances add-metadata <instance-name> --zone <instance-zone> --metadata startup-script='#! /bin/bash 
hostname <hostname>'

Notice that if you already have a startup-script you need to add to the existing startup-script below command or you will replace all the startup-script:

$ hostname instance-name

score 3 · Answer 6 · answered Jan 08 '18 at 14:03

I was lucky to set hostname at GCE running CentOS. Source: desantolo.com

Click EDIT on your instance
Go to "Custom metadata" section
Add hostname + your.hostname.tld (change "your.hostname.tld" to your actual hostname
run curl --silent "http://metadata.google.internal/computeMetadata/v1/instance/attributes/hostname" -H "Metadata-Flavor: Google"
run sudo env EDITOR=nano crontab -e to edit crontab
add line @reboot hostname $(curl --silent "http://metadata.google.internal/computeMetadata/v1/instance/attributes/hostname" -H "Metadata-Flavor: Google")
On your keyboard Ctrl + X
On your keyboard hit Y
On your keyboard hit Enter
run reboot
after system rebooted, run hostname and see if your changes applied

Good luck!

score 2 · Answer 7 · answered Mar 22 '18 at 01:07

If anyone finds this solution does not work for them on GCS instance. Then I suggest you try using exit hooks as described by Google Support.

In fact, some distributions of Linux like CentOS and Debian use dhclient-script script to configure the network parameters of the machine. This script is invoked from time to time by dhclient which is dynamic host configuration protocol client and provides a means for configuring one or more network interfaces using the DHCP protocol, BOOTP protocol, or if these protocols fail, by statically assigning an address.

The following text is a quote from the man (manual) page of dhclient-script:

After all processing has completed, /usr/sbin/dhclient-script checks for the presence of an executable /etc/dhcp/dhclient-exit-hooks script, which if present is invoked using the ´.´ command. The exit status of dhclient-script will be passed to dhclient-exit-hooks in the exit_status shell variable, and will always be zero if the script succeeded at the task for which it was invoked. The rest of the environment as described previ‐ ously for dhclient-enter-hooks is also present. The /etc/dhcp/dhclient-exit-hooks script can modify the valid of exit_status to change the exit status of dhclient-script.

That being said, by taking a look into the code snippet of dhclient-script, we can see the script checks for the existence of an executable /etc/dhcp/dhclient-up-hooks script and all scripts in /etc/dhcp/dhclient-exit-hooks.d/ directory.
ETCDIR="/etc/dhcp"

193 exit_with_hooks() {
194     exit_status="${1}"
195 
196     if [ -x ${ETCDIR}/dhclient-exit-hooks ]; then
197         . ${ETCDIR}/dhclient-exit-hooks
198     fi
199 
200     if [ -d ${ETCDIR}/dhclient-exit-hooks.d ]; then
201         for f in ${ETCDIR}/dhclient-exit-hooks.d/*.sh ; do
202             if [ -x ${f} ]; then
203                 . ${f}204             fi
205         done
206     fi
207     
208     exit ${exit_status}209 }
Therefore, in order to modify the hostname of your Linux VM you can create a custom script with .sh extension and place it in /etc/dhcp/dhclient-exit-hooks.d/ directory. If this directory does not exist, you can create it. The content of the custom script will be:
hostname YourFQDN.sh

>

be sure to make this new .sh file executable:
 chmod +x YourFQDN.sh

Source: (https://groups.google.com/d/msg/gce-discussion/olG_nXZ-Jaw/Y9HMl4mlBwAJ)

score 1 · Answer 8 · answered Feb 11 '15 at 01:41

1

Im not sure I understand Adrián's answer. It seems overly complex since you have to run a script each boot why not just use hostname?

vi /etc/rc.local

add:

hostname your_hostname

thats it. tested and working. no need to fiddle with metadata and such.

answered Feb 11 '15 at 01:41

tgwaste

439
3
7

I think Adrián's solution is good when you want to change the hostname by just changing metadata of your instance. You can clone the server, change the metadata and it will work. Otherwise you need to log into the server, edit the file, change the hostname, etc. – dgaviola Sep 29 '15 at 14:50
Perhaps this will help someone; the reason this is not viable is because GCE resets the hostname every reboot, unless one of the solutions described above is used. (script, cron) – Adam John May 17 '18 at 21:48

score 1 · Answer 9 · answered Dec 08 '17 at 16:16

1

Non-cron/metadata/script solution.

Edit /etc/dhclient-(network-interface).conf or create one if it doesn't exist.

Example:

sudo nano /etc/dhclient-eth0.conf

Then add the following line, replacing the desired FQDN between the double quotes:

supersede host-name "hostname.domain-name";

Persists between reboots and hostname and hostname -f works as intended.

answered Dec 08 '17 at 16:16

David Garrana

11
1

In Centos7 working but if added "something.com" then only something is showing on hostname, Period is skipping – Rahul Sharma Dec 28 '17 at 06:06
That's the expected behavior, to display _something.com_, "-f" argument is required to hostname command, as in: `hostname -f` – David Garrana Jan 02 '18 at 12:05

score 1 · Answer 10 · answered Apr 10 '18 at 14:09

Tested on Debian.

The dhclient sets the hostname using DHCP

You can override this by creating a custom hook script in /etc/dhcp/dhclient-exit-hooks.d/custom_set_hostname that would read the hostname from /etc/hostname:

if [ -f "/etc/hostname" ]; then
    new_host_name=$(cat /etc/hostname)
fi

The script must have the execute permission.

It's important to set the new_host_name variable and not calling the hostname command directly as any call to the hostname command will be overriden by another hook or the dhclient-script which uses this variable

score 1 · Answer 11 · answered Nov 09 '18 at 18:49

When creating a VM, you can specify a custom FQDN hostname as an optional parameter. This feature is currently in Beta.

$ gcloud beta compute instances create INSTANCE_NAME --hostname example.hostname

This should work across OSes, and prevent the need for workaround scripts. More info in the docs.

-- Sirui (Product Manager, Google Compute Engine)

score 0 · Answer 12 · answered Feb 08 '18 at 05:11

In my CentOS VMs I found that the script /etc/dhcp/dhclient.d/google_hostname.sh, installed by the google-compute-engine RPM, actually changed the hostname. This happens when the instance gets its IP address during boot.

While it's not the long-term solution I really want, for now I simply deleted this script. The hostname I set with hostnamectl now persists after a reboot.

The script is likely to be in exactly the same place in Debian/Ubuntu VMs, but of course I don't run any of those.

score 0 · Answer 13 · answered Feb 15 '19 at 11:59

There is some hack you can do to achieve this as i did. Just do:

sudo chattr +i /etc/hosts

This command actually 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

Cheer!

score 0 · Answer 14 · edited Dec 08 '20 at 05:06

0

An easy way to fix this is to set up a startup script with custom metadata.

Key :startup-script 
Value: 
#! /bin/bash 
hostname <desired hostname>

edited Dec 08 '20 at 05:06

Kirby

15,127
10
89
104

answered Dec 07 '20 at 19:35

user14782359

1

Google Compute Engine: how to set hostname permanently?

14 Answers14

Linked