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SYS-C0046 · Linux Command Builders

Configuring Network with Netplan

Draft one netplan file for one interface, and apply it only with a console open.

Updated 25 October 2026 · How-To

This is an original planning guide. It is not a vendor manual, an official standard, or legal advice. Example addresses use documentation ranges. Review every command before you paste it.

What this hour is for

Netplan is YAML under /etc/netplan. The generator drafts a file. It does not apply it. The interface name comes from the host, not from an example. 192.0.2.10/24 and gateway 192.0.2.1 are documentation.

netplan apply can drop the session you are using. The console or the out-of-band path is open first, and you test that path before the apply. This page does not tell you to apply during the reading.

A Debian interfaces file is not netplan. Do not paste one into the other. Do not invent an interface name. 192.0.2.10/24 and example.com are documentation. They stay in the note.

The change you can finish

Apply nothing while you are writing the note. When the lab window opens, it is one change on the host named in the ticket. Read the draft, then the host, then decide.

Rollback is the file, the package version, or the snapshot you saved first. You do not invent a rollback after the only copy is gone.

  1. Read the interface name from the host, later.
  2. Write the address the network desk assigned, or a documentation address labeled as lab.
  3. Draft the YAML.
  4. Delete any interface you did not see.
  5. Do not apply during the reading.
  6. Write down the console path.

Mistakes that outlive the command

Configuring Network with Netplan goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.

Decisions to write down

One decision for Configuring Network with Netplan: One interface. The address is labeled lab or assigned. The console path is known. Apply is not part of the reading. And the file is netplan, not interfaces.

Checks before you call it done

Confirm this before you call the change done: The interface name is written. The address is written. The YAML was read. No apply was done. And the console path is in the ticket. If one of those fails, stop.

# netplan YAML. Not a Debian interfaces file.
# 192.0.2.10/24 is documentation.
# Do not apply during the reading.
# Console first.

Before you leave the host

Configuring Network with Netplan ends when the hostname in the prompt matches the hostname in the ticket. If it does not, you are on the wrong host. Stop. A command that succeeded on the wrong host is not progress.

The draft stays a draft until a person has read the names in it. A generator does not log into the host and does not know which disk is empty. You delete a line that names a host, a path, or an account you did not write down.

192.0.2.10/24, gateway 192.0.2.1, 198.51.100.0/24, 203.0.113.0/24, and 2001:db8::/32 are documentation. example.com is a documentation name. They belong in the note. They are not values you leave on a host because a draft included them.

prompt-for-this is a reminder that a secret is missing. It is not a password, a key, or a token you save in the ticket or in git. The real secret stays in the password store.

One change is the window. If two things move and the result is wrong, you will not know which one did it. The next change waits for its own page.

If the same step fails twice, stop for the day. The failure is the result. Adding a forum command beside a half-applied change produces a host nobody can rebuild. Restore the copy you took first.

A second person reads the hostname and the change aloud. If they cannot find them in the ticket, the note is not done. Silence is not agreement. Then leave the host alone.

This page is a planning guide. It is not a vendor manual, not an official standard, and not permission to touch a host you do not administer. You do not disable a firewall, AppArmor, or SELinux to make a check pass.

Tools for this guide

These tools run in the browser on this site. They do not log into your machines.

More in this cluster

The pillar for this page, and the next published pages filed with it.

Companion: Network: Subnetting Explained Step by Step.