Public bug reported:
### Description
When installing Ubuntu (versions 26.04 and 26.10) inside a Virtual
Machine with the Network Interface Card (NIC) disabled during
installation, powering off the VM, cloning it, and subsequently turning
on the NIC in the clone results in a system where internet connectivity
does not initialize automatically at boot.
In contrast, **Ubuntu MATE 26.10 handles this scenario correctly**, and
internet connectivity works out of the box when the NIC is enabled on
the clone, even though its default configuration
(`/etc/netplan/00-installer-config.yaml`) does not explicitly contain a
`dhcp4` directive and looks like this:
```yaml
# This is the network config written by 'subiquity'
network:
ethernets: {}
version: 2
```
---
### Steps to Reproduce
1. Create a Virtual Machine with the NIC disabled or disconnected.
2. Complete the installation of Ubuntu 26.04 or 26.10 inside the VM.
3. Power off the Virtual Machine and create a clone of it.
4. Enable the NIC on the cloned VM, then power it on.
5. Check if internet connectivity connects automatically at boot.
---
### Expected Result
Internet connectivity should connect automatically at boot once the NIC
is turned on in the cloned VM, consistent with the behavior observed in
Ubuntu MATE.
---
### Actual Result
Internet connectivity does not connect automatically at boot when booted
with the NIC enabled on standard Ubuntu installations.
---
### Additional Information / Workaround
Unlike standard Ubuntu, Ubuntu MATE 26.10 works seamlessly out of the
box regardless of whether the NIC was on or off during installation,
without requiring manual Netplan adjustments.
As a temporary workaround for standard Ubuntu installations, the
following script can be used to resolve the issue:
```bash
if grep -q '^ID=ubuntu' /etc/os-release && \
grep -q '^VERSION_ID="26\.' /etc/os-release && \
grep -Eq '^Ubuntu [0-9]' /var/log/installer/media-info 2>/dev/null; then
IFACE=$(ip -4 route show default | awk '{print $5}' | head -n1)
[ -z "$IFACE" ] && IFACE="enp1s0"
# Check if DHCP is already configured
DHCP4_SET=$(netplan get ethernets."$IFACE".dhcp4 2>/dev/null)
DHCP6_SET=$(netplan get ethernets."$IFACE".dhcp6 2>/dev/null)
if [ "$DHCP4_SET" != "true" ] || [ "$DHCP6_SET" != "true" ]; then
sudo netplan set ethernets."$IFACE".dhcp4=true
sudo netplan set ethernets."$IFACE".dhcp6=true
sudo netplan generate
sudo netplan apply
# Wait for WAN and DNS so premature apt runs don't fail InRelease checks
until wget -q --spider --timeout=1 http://archive.ubuntu.com; do
sleep 1
done
fi
sudo apt-get update
fi
```
** Affects: ubuntu
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2170258
Title:
Netplan fails to configure DHCP on first boot when installed with NIC
disabled then enabled
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