Troubleshoot nova-agent or Rackspace Cloud Server Agent -

Troubleshoot nova-agent or Rackspace Cloud Server Agent

Last updated on: 2020-07-06

Authored by: Chris Silva, Brian Abshier

This article describes the nova-agent service on Linux® servers and Rackspace Cloud Server Agent on Windows®.

What is `nova-agent`?

nova-agent is a vital service for all virtualized servers in the Rackspace public cloud. While a cloud server is operational, nova-agent provides a way to interact with the server through the API or the Cloud Control Panel. nova-agent enables components outside the server to control the server by sending messages through the Xen® XenStore file system. For example, when an authorized user of the Cloud Control Panel sends the server a request to reset a password, the Cloud Control Panel writes the request to XenStore, and nova-agent then reads from XenStore and informs the server.

How does `nova-agent` affect my server?

When you initialize a cloud server, nova-agent performs startup functions such as configuring the server’s network, establishing its hostname, and setting its root or admin passwords.

The normal operation of a cloud server requires nova-agent to remain active. Disabling or removing nova-agent can result in issues with the server interfacing with the host environment. We do not recommend removing or disabling the service on your server.

`nova-agent` dependencies

nova-agent relies on another service being started and running on the server first, xe-linux-distribution (in some operating systems, it is called xe-daemon.) This service is responsible for allowing the virtual machine (VM) to communicate with the hypervisor via XenStore. The xe-guest-utilities package, installed by default on all Linux servers on the Rackspace Cloud, provides the xe-linux-distribution service. Because nova-agent relies on XenStore to function, you should make sure that xe-linux-distribution starts before the nova-agent service.

On Windows servers, the dependency is known as Citrix Xen Windows Guest Agent. This service performs the same duties as the xe-linux-distribution does for a Linux server. This service also is installed and starts automatically by default on all base Windows images.

How is my server affected if `nova-agent` is broken or missing?

Without the nova-agent service running on your server, the following issues occur:

Unable to reset the root/Administrator password through your portal.
Unable to add or remove networks or set proper IPs or routes
No Red Hat® Enterprise Linux® registration or Windows Activation

Note: New servers created from a Cloud Image without nova-agent result in build failures. The server build process completes, but networking and root or Administrator password issues are likely. The best solution for this kind of issue is to fix nova-agent on the source server, capture a new image, and use the new image to build your server.

Check the `nova-agent` status on Linux servers

To make sure that nova-agent is running on your Linux server, run one of the following commands:

Red Hat Enterprise Linux 6, CentOS® 6:
```
   service nova-agent status
```
Red Hat Enterprise Linux 7, CentOS 7:
```
   systemctl status nova-agent
```
Debian®-based distributions:
```
   systemctl status python3-nova-agent
```

You can also verify the process is running on all OS versions with the following command:

     ps aux | grep -i nova-agent

Check the `nova-agent` status on Windows servers

To check the nova-agent status on Windows servers, perform the following steps:

Open the Server Manager within Windows.
Select Tools.
Select Services.
Right-click the Rackspace Cloud Server Agent service and choose Start.

Start and enable `nova-agent` on Linux servers

To start and enable the service on boot for a Linux server, run one of the following commands:

Red Hat Enterprise Linux 6 and CentOS 6:
```
 chkconfig nova-agent on
```
Red Hat Enterprise Linux 7 and CentOS 7:
```
 systemctl enable nova-agent
```
Debian-based distributions:
```
systemctl enable python3-nova-agent
```

Start and enable `Rackspace Cloud Server Agent` on Windows servers

To start and enable the Rackspace Cloud Server Agent on Windows servers, perform the following steps:

Open the Server Manager within Windows.
Select Tools.
Select Services.
Right-click the Rackspace Cloud Server Agent service and choose Properties.
Change the Startup Type to Automatic and click Apply/OK.

Rescue mode troubleshooting

As noted above, the nova-agent is responsible for managing password changes. If you can’t access your server after changing the password, the nova-agent service might have stopped.

If you can’t access your server, you need to enter Rescue Mode and troubleshoot. See Rescue Mode for more information.

Rescue Mode on a Linux Server

After you boot the server in Rescue Mode and log into the server, use the following commands to change the root password and enable nova-agent:

Make a temporary directory by running the following command:
```
 mkdir /mnt/rescue
```
Mount the filesystem to the temporary directory by running the following commands:
```
 mount /dev/xvdb1 /mnt/rescue
 chroot /mnt/rescue
```
Run the passwd command to change the root password by running the following command and entering the new password twice:
```
 passwd
```
Enable the nova-agent service by running the following command:
- Red Hat Enterprise Linux 6 and CentOS 6:
```
chkconfig nova-agent on
```
- Red Hat Enterprise Linux 7 and CentOS 7:
```
systemctl enable nova-agent
```
- Debian-based distributions:
```
systemctl enable python3-nova-agent
```
Note: Older and unsupported versions of Debian-based operating systems might refer to the service as nova-agent. As a best security practice, if an operating system has reached end-of-life (EOL), we strongly recommend that you migrate to a server with a newer operating system.
Exit out of chroot mode by running the following command:
```
 exit
```
Unmount the temporary filesystem by running the following command:
```
 umount /mnt/rescue
```

At this point, you can disconnect from the server and exit Rescue Mode. Upon rebooting the server, you should now be able to access the server via the password created in the preceding steps. Additionally, the nova-agent service should be running on the server. You can verify the service is running, as shown in the previous section.

Rescue Mode on a Windows Server

Rescue mode on a Windows server functions differently than a Linux server. On a Windows server, when a rescue server is created, you are given access to your filesystem so that you can access your data, but you cannot modify your server’s system configuration. This restriction means you cannot set the Rackspace Cloud Server Agent to start automatically from within Rescue Mode. If you’ve locked yourself out of your Administrator account, and have no other accounts that you can use to connect over RDP or the Emergency Console, contact Rackspace Support.

Cloud Servers