84 lines
3.2 KiB
Markdown
84 lines
3.2 KiB
Markdown
---
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title: "VM-Operator: Auto login — Login users automatically on the guest"
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layout: vm-operator
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---
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# Auto Login
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*Since 4.0.0*
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When a user logs in on the web GUI, he has already authenticated with the
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VM-Operator. Depending on the environment, it may be tedious to log in again
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on the guest. The VM-Operator therefore supports automatic login on the guest
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operating system which can streamline the user experience by eliminating
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the need for multiple logins. This requires, however, some support from
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the guest OS.
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## Prepare the VM
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Automatic login requires an agent in the guest OS. Similar to QEMU's
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standard guest agent, the VM-Operator agent communicates with the host
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through a tty device (`/dev/virtio-ports/org.jdrupes.vmop_agent.0`). On a modern
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Linux system, the device is detected by `udev` which triggers the start
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of a systemd service.
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Sample configuration files can be found
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[here](https://github.com/mnlipp/VM-Operator/tree/main/dev-example/vmop-agent).
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Copy
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* `99-vmop-agent.rules` to `/usr/local/lib/udev/rules.d/99-vmop-agent.rules`,
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* `vmop-agent` to `/usr/local/libexec/vmop-agent` and
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* `vmop-agent.service` to `/usr/local/lib/systemd/system/vmop-agent.service`.
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Note that some of the target directories do not exist by default and have to
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be created first. Don't forget to run `restorecon` on systems with SELinux.
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Enable everything:
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```console
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# systemctl daemon-reload
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# systemctl enable vmop-agent
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# udevadm control --reload-rules
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# udevadm trigger
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```
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## The VM operator agent
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Communication with the VM-Operator agent follows the pattern established
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by protocols such as SMTP and FTP. The agent must handle the commands
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"`login <username>`" and "`logout`". In response to these commands, the agent
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sends back lines that start with a three digit number. The first digit
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determines the type of message: "1" for informational, "2" for success
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"4" and "5" for errors. The second digit provides information about the
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category that the response relates to. The third digit is specific to
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the command.
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While this describes the general pattern, the only response code that
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the runner evaluates are:
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| Code | Meaning |
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| ---- | ------- |
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| 220 | Sent by the agent on startup |
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| 201 | Login command executed successfully |
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| 202 | Logout command executed successfully |
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The sample script is written for the gnome desktop environment. It assumes
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that gdm is running as a service by default. On receiving the login command,
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it stops gdm and starts a gnome-session for the given user. On receiving the
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logout command, it terminates the session and starts gdm again.
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No attempt has been made to make the script configurable. There are too
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many possible options. The script should therefore be considered as a
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starting point that you can adapt to your needs.
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The sample script also creates new user accounts if a user does not exist
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yet. The idea behind this is further explained in the
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[section about pools](pools.html#vm-pools).
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## Enable auto login for a VM
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To enable auto login for a VM, specify the user to be logged in in the VM's
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definition with "`spec.vm.display.loggedInUser: user-name`". If everything has been
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set up correctly, you should be able to open the console and observe the
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change from gdm's login screen to the user's desktop when updating the
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VM's spec.
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