Unable to set hostname through DHCP

[vincentbernat]

Hey!

Sending host-name option through DHCP is mostly ignored due to how hostname.sh works:

1. OpenBMC boots
2. dhclient gets its DHCP lease containing a host-name option
3. dhclient-script sets the hostname using the hostname command
4. hostname.sh overrides the hostname with either bmc-oob or with hostname stored in /mnt/data/hostname and store the result in /mnt/data/hostname.

Also, if there is no network connectivity on boot:

1. OpenBMC boots
2. dhclient is unable to get a lease and will go on background
3. hostname.sh will sets and store it in /mnt/data/hostname
4. network connectivity comes back
5. dhclient gets a lease and host-name
6. dhclient-script won't update the hostname as one is already set

In case systemd is used, this is the same logic in networkd, except the hostname seems to be set even when a hostname already is set (I didn't test).

I would suggest to not change hostname if one already exists (as per hostname command). This wouldn't solve the second case, except with systemd.