Switch from NetworkManager to dhclient

NetworkManager is a memory hog.  We don't need it to do anything except
renew the DHCP lease when it's time, so let's switch to a more
lightweight alternative.  Unfortunately, Fedora does not include any
systemd units for `dhclient`, so we have to provide our own.

mkrootfs.sh

@@ -18,6 +18,7 @@ echo install_weak_deps=False >> "${destdir}"/etc/dnf/dnf.conf
 
 dnf --installroot "${destdir}" install -y \
     bcm2711-firmware \
+    dhcp-client \
     dracut-network \
     firefox \
     hostname \
@@ -28,7 +29,6 @@ dnf --installroot "${destdir}" install -y \
     openssh-server \
     rsyslog \
     systemd \
-    systemd-resolved \
     xinit \
     xorg-x11-server-Xorg \
     xset \
@@ -59,12 +59,14 @@ if ! grep -qE '^video:.*:.+:.*,?user' "${destdir}"/etc/group; then
     chroot "${destdir}" gpasswd -a user video
 fi
 chroot "${destdir}" systemctl enable \
+    dhclient@eth0 \
     systemd-time-wait-sync \
     systemd-timesyncd \
     xinit@user
 chroot "${destdir}" systemctl disable \
     systemd-homed \
     systemd-userdbd
+ln -sf /run/resolv.conf "${destdir}"/etc/resolv.conf
 
 umask 0022
 mksquashfs "${destdir}" "${destdir}/boot/${dest}" \

overlay/etc/dhcp/dhclient.conf

@@ -0,0 +1,10 @@
+option classless-static-routes code 121 = array of unsigned integer 8;
+
+send dhcp-client-identifier = hardware;
+
+request subnet-mask, broadcast-address, time-offset, routers,
+        domain-name, domain-name-servers, domain-search, host-name,
+        root-path, interface-mtu, classless-static-routes,
+        netbios-name-servers, netbios-scope, ntp-servers,
+        dhcp6.domain-search, dhcp6.fqdn,
+        dhcp6.name-servers, dhcp6.sntp-servers;

overlay/etc/fstab

@@ -1,7 +1,6 @@
 tmpfs /var/lib/rsyslog tmpfs defaults 0 0
 tmpfs /var/log tmpfs defaults 0 0
 tmpfs /var/lib/systemd tmpfs defaults 0 0
-tmpfs /var/lib/NetworkManager tmpfs defaults 0 0
 /dev/mmcblk0 /run/storage ext4 ro,noexec,nosuid,nodev,x-systemd.makefs 0 2
 overlay /etc/ssh overlay ro,lowerdir=/etc/ssh:/run/storage/ssh,noexec,nodev,nosuid,x-systemd.requires-mounts-for=/run/storage 0 0
 /dev/nbd1 swap swap noauto,x-systemd.makefs 0 0

overlay/etc/systemd/system/dhclient@.service

@@ -0,0 +1,13 @@
+[Unit]
+Description=DHCPv4 client for %I
+Before=network-online.target
+Before=network.target
+
+[Service]
+Type=forking
+RuntimeDirectory=dhclient
+ExecStart=/usr/sbin/dhclient -4 -1 -lf /run/dhclient/%I.lease -pf /run/dhclient/%I.pid
+PIDFile=/run/dhclient/%I.pid
+
+[Install]
+WantedBy=multi-user.target