Using the mkinitcpio net hook confuses netcfg

Question

Hello everybody.
I am currently trying to build a headless Linux home server, and I decided to try out Arch.
The server has an encrypted root file system by means of having a plain-text /boot 1st partition and having the / file system on a 2nd LUKS partition.
For starters I used the mkinitcpio hooks "keymap keyboard encrypt", with the appropriate "cryptdevice=..." and "root=..." kernel parameters to make the server prompt me for the pass phrase in early user space, which works nicely.
As this thing is supposed to become a headless system I then tried to set it up in a way that enables me to open an SSH connection into the early user space and supply the pass phrase from there, using dropbear_initrd_encrypt. And it works! This is great stuff.
Unfortunately doing this broke the then-running server's network connection.
I have a static IP address netcfg profile that is loaded from systemd on server start-up (systemctl enable netcfg; the profile is set in the "NETWORKS=..." variable in "/etc/conf.d/netcfg").
The ethernet device is called "enp2s0".
This worked flawlessly until I started using the "net" mkinitcpio hook to get a network connection in early user space for the remote unlocking.
The net hook's corresponding kernel parameter looks like "ip=<ip>:::<netmask>:::none"
When I use this hook, the system boots up without having the "enp2s0" ethernet device, causing netcfg to bail out.
It does however gain the same network device as "eth0" instead, which is apparently how early user space calls it. This "eth0" ethernet device appears to retain the settings it has been set up with by the net hook.
Unfortunately the net hook does not supply things like a default gateway or DNS servers, so while the server technically is reachable from the local network, it cannot access the internet, which it definitely needs to be able to do.
After tracking this down I figured "Whatever. I can live with the ethernet device being called eth0."
So I made a second identical netcfg profile, exchanging "enp2s0" for "eth0", and set the server to load that one instead when booting.
That unfortunately did not work either, because netcfg is cautious and aborts when it is told to set up a network adapter that is already active in some way unknown to netcfg.
What also didn't help was specifying the "enp2s0" ethernet device name in the "ip=..." kernel parameter for the net hook, because indeed the early user space only knows the device as "eth0".
So for now I'm stumped. Anyone experienced this issue and managed to solve it?
A solution might be another "disablenet" mkinitcpio hook that deconfigures the network adapters configured by "net", so that the renaming from "eth0" to "enp2s0" during boot, which I assume fails on account of "eth0" being active, works again.
Thanks for any help,
eomanis
Edit: Changed "netctl" to "netcfg" in the thread subject
Last edited by eomanis (2013-04-18 08:45:21)

Answer 1

tomk wrote:You could try including the appropriate command to bring down your interface in your profile's PRE_UP field.
Okay, I tried that.
I put both netcfg profiles into the "NETWORKS=..." variable in "/etc/conf.d/netcfg", and added this to both of them:
# Clear leftover state from mkinitcpio net hook
PRE_UP="ip link set <device> down || true"
where <device> is eth0 or enp2s0, respectively.
After a reboot with remote decryption the server's network was down completely. Looks like the "ip link set ... down" command worked all right, but the rest didn't go as planned.
Here's what systemctl says about that:
[root@hserver autologin]# systemctl status netcfg
netcfg.service - Netcfg multi-profile daemon
Loaded: loaded (/usr/lib/systemd/system/netcfg.service; enabled)
Active: failed (Result: exit-code) since Thu 2013-04-18 22:35:38 CEST; 26min ago
Process: 340 ExecStart=/usr/bin/netcfg-daemon start (code=exited, status=1/FAILURE)
Apr 18 22:35:35 hserver netcfg-daemon[340]: :: static_enp2s0 up Cannot find device "enp2s0"
Apr 18 22:35:35 hserver netcfg-daemon[340]: Interface enp2s0 does not exist
Apr 18 22:35:35 hserver netcfg-daemon[340]: [fail]
Apr 18 22:35:38 hserver netcfg-daemon[340]: :: static_eth0 up RTNETLINK answers: File exists
Apr 18 22:35:38 hserver netcfg-daemon[340]: Could not configure interface
Apr 18 22:35:38 hserver netcfg-daemon[340]: [fail]
Apr 18 22:35:38 hserver systemd[1]: netcfg.service: main process exited, code=exited, status=1/FAILURE
Apr 18 22:35:38 hserver systemd[1]: Failed to start Netcfg multi-profile daemon.
Apr 18 22:35:38 hserver systemd[1]: Unit netcfg.service entered failed state
As before, device "enp2s0" is missing, but "eth0" doesn't come up either, even after being downed manually beforehand :-(
Strangely enough, if I do "netcfg -u static_eth0" after that, eth0 does come up. What?!
@falconindy: Applying a udev rule in early user space would require to make a custom initcpio hook, wouldn't it?
In that case I'd rather try to figure out what the "net" hook does and undo it, seeing that I have to write a custom hook anyway and that "eth0" doesn't come up no matter what.
Having an "enp2s0" ethernet device that doesn't come up either isn't going to do me much good ;-)
Thanks for the suggestions,
eomanis