Where is the variable?

[Roguito]

I assume there was a step that was supposed to set the token env variable before these instructions.

2) Setup environment variable for the token
Use the variable below to install an agent (worker) node

curl -sfL https://get.rke2.io | INSTALL_RKE2_TYPE="agent" sh -

[Roguito]

if it was meant to be used as an environment variable as part of an automated bash script. I suggest:
token=$(cat /var/lib/rancher/rke2/server/node-token)

[malcolmlewis]

The token needs to be copied over to the node the install is on, that variable is only on the initial machine. Or just create your own to use which is what I do and place in /etc/rancher/rke2 directory...