Configure DNS name for network-address without stop/start

[huguesb]

Description

I need a colima machine to have its own IP so I can reach exposed ports from the host. I am using --network-address for that.

I want to map this IP to a custom domain name. I can easily do that by adding an entry to /etc/hosts on my host machine. I wrote a small script to automatically detect the IP addres used by colima and update /etc/hosts as needed (using colima status --json | jq -r .ip_address and comparing with the output of dscacheutil). So far so good.

Now, I also need this custom domain name to be resolvable to the same IP within docker containers on the colima machine, and this is where I'm a little frustrated.

The networking stack inside the colima VM does not seem to pick up the change to /etc/hosts on the macOS host. I can make edits to /etc/hosts on the VM but those are not picked up by docker containers.

I very much do not want to have to manually pass extra host entries to every container I start, and have to update those if the IP ever changed upon a VM restart.

As far as I can tell, the only way to achieve my goal is to follow this sequence:

colima start --network-address
ip=$(colima status --json | jq -r .ip_address)
colima stop
colima start --dns-host "my.custom.domain=$ip"

and hope the IP of the machine will not change on restart (is that a safe assumption? I have no idea...)

In general, I would like to have a way to update DNS config without stopping the machine. Ideally, it would be nice if the internal resolver for the bridge interface honored the hosts' /etc/hosts by default.

As a special case, for a short-term workaround, I would be okay if the auto-assigned machine IP was resolved to a fixed domain by the internal DNS, so I can easily alias my custom name to that immediately when first creating the machine.

[abiosoft]

and hope the IP of the machine will not change on restart (is that a safe assumption? I have no idea...)

It is a safe assumption. The IP address is generated using the mac address of the virtual network interface. As long as the VM has not been destroyed and re-created, the IP address would remain.

The networking stack inside the colima VM does not seem to pick up the change to /etc/hosts on the macOS host. I can make edits to /etc/hosts on the VM but those are not picked up by docker containers.

I actually assume that this should work, probably a bug.

The docker containers can definitely reach the VM via the (fixed) IP address. Maybe it makes sense to add (as an in-built feature) a dns entry that resolves to the VM's IP address. Considring the macOS host is available via host.docker.internal.