RTNETLINK answers: File exists

RTNETLINK answers: File exists

TL;DR: the address or route wg-quick wants to add is already on the interface from an earlier run. Bring the interface down first with wg-quick down wg0, confirm it is gone, then bring it up again.

RTNETLINK answers: File exists

Steps

1. Take the interface down cleanly:

sudo wg-quick down wg0

Expected: no output, and ip link show wg0 reports the device does not exist.

2. If it is still there, remove the leftover address by hand:

sudo ip link delete wg0

Expected: ip link show wg0 finds nothing.

3. Bring it up again:

sudo wg-quick up wg0

Expected: the interface comes up with no RTNETLINK complaint, and wg show lists your peers.

When this applies

• wg-quick up after a previous up half-succeeded or was killed
• the interface was created manually with ip link add and then wg-quick ran
• Address lines duplicated across config files

When it doesnt

• wg-quick: 'wg0' already exists — that is the interface-level twin of this error
• Key is not the correct length or format — a key problem, not an address one
• no route to the peer — that is routing, not this

Compatibility

wireguard-tools wg-quick on Linux.

Other phrasings

• RTNETLINK answers: File exists wg-quick up
• wireguard File exists on up

Why it happens

wg-quick is a script that adds addresses and routes one by one. It does not check first whether they already exist, so any leftover from a crashed or manual setup makes the kernel refuse the duplicate.

Edge cases

• If wg-quick down says the interface is not defined, the config name and interface name may differ; match them.
• NetworkManager or systemd-networkd fighting over the same interface can recreate the conflict; pick one manager.