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Francis
Asked: 2020-10-23 08:12:26 +0800 CST

How to drop dhcp ip assignated when using clevis/tang on Ubuntu 20.04

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I unlock my drive with clevis/tang on an Ubuntu server (NBDE). It works fine, but even if my server is configured to use a static ip in /etc/netplan/01-netcfg.yaml, my network interface also listen on two dhcp ip attributed on the boot process. How to drop it after boot is completed?

I enabled clevis with the following commands:

sudo apt install clevis clevis-systemd clevis-initramfs clevis-luks
sudo clevis luks bind -d /dev/sda3 sss '{"t": 1, "pins": {"tang": [{"url": "http://10.1.1.1:8888"},{"url": "http://10.2.2.2:8888"}]}}' 
sudo update-initramfs -u -k 'all'

After rebooting my server, the network interface got 3 ips! My static ip configured in /etc/netplan and two dhcp ips. One of the dhcp ip is used by the clevis process (I see a trace on my tang server). The other seem to be assigned after the clevis process is completed.

I was able to make clevis to drop the dhcp ip it use. I noticed that the script at /usr/share/initramfs-tools/scripts/local-bottom/clevis was different than the one in the clevis git repository. I added the line iface=$(basename "$iface") after if [ -e "$iface" ]; then.

But I'm still stuck with one useless dhcp ip on my interface. When I do a netplan apply, systemd-networkd even refresh the dhcp lease as you can the in the following log extract:

Oct 22 12:04:56 testserver systemd[1]: Reloading.
Oct 22 12:04:56 testserver systemd[1]: /lib/systemd/system/dbus.socket:5: ListenStream= references a path below legacy directory /var/run/, updating /var/run/dbus/system_bus_socket → /run/dbus/system_bus_socket; please update the unit file accordingly.
Oct 22 12:04:56 testserver systemd[1]: systemd-networkd-wait-online.service: Succeeded.
Oct 22 12:04:56 testserver systemd[1]: Stopped Wait for Network to be Configured.
Oct 22 12:04:56 testserver systemd[1]: Stopping Network Service...
Oct 22 12:04:57 testserver systemd[1]: systemd-networkd.service: Succeeded.
Oct 22 12:04:57 testserver systemd[1]: Stopped Network Service.
Oct 22 12:04:57 testserver systemd[1]: Condition check resulted in OpenVSwitch configuration for cleanup being skipped.
Oct 22 12:04:57 testserver systemd[1]: Starting Network Service...
Oct 22 12:04:57 testserver systemd[1]: Condition check resulted in OpenVSwitch configuration for cleanup being skipped.
Oct 22 12:04:57 testserver systemd-networkd[1711]: eno3: Gained IPv6LL
Oct 22 12:04:57 testserver systemd-networkd[1711]: Enumeration completed
Oct 22 12:04:57 testserver systemd[1]: Started Network Service.
Oct 22 12:04:57 testserver systemd-networkd[1711]: eno3: IPv6 successfully enabled
Oct 22 12:04:57 testserver systemd-networkd[1711]: eno3: DHCPv4 address 10.1.1.71/21 via 10.1.0.1

But I don't use dhcp at all in my netplan configuration!

# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network:
  version: 2
  #renderer: networkd
  ethernets:
    eno3:
      dhcp4: no
      addresses:
      - 10.1.0.99/21
      gateway4: 10.1.0.1
      nameservers:
        addresses:
        - 10.1.0.3
        - 10.1.0.33

When I launch netplan --debug apply, I see that dhcp4 become enabled when the config is merged!? But merged with what? Can be from /run/netplan/eno3.yaml? In that file, I see a dynamic network configuration with dhcp enabled. What does generate that file?

ubuntu ubuntu-20.04 netplan systemd-networkd

1 Answers

  1. Best Answer

    Seem like there is a bug in a clevis script. Edit /usr/share/initramfs-tools/scripts/local-bottom/clevis.

    Search:

    for iface in /sys/class/net/*; do
    if [ -e "$iface" ]; then
        ip link  set   dev "$iface" down
        ip addr  flush dev "$iface"
        ip route flush dev "$iface"
    fi
done

    Replace with:

    for iface in /sys/class/net/*; do
    if [ -e "$iface" ]; then
        iface=$(basename "$iface")
        ip link  set   dev "$iface" down
        ip addr  flush dev "$iface"
        ip route flush dev "$iface"

        if [ -f "/run/netplan/${iface}.yaml" ]; then
            rm "/run/netplan/${iface}.yaml"
        fi
    fi
done

    Regenerate initramfs with the following command: update-initramfs -u -k 'all' then reboot.

    The file /run/netplan/eno3.yaml is gone and all the stall dhcp addresses are also gone from the interface!

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