Thursday, May 21, 2009

No Drives Found error installing CentOS 5.2 on VMWare

Ok, so this is not my typical blog post that talks about anything Microsoft but it still is technology so it makes a good blog post.

I was installing CentOS 5.2 on a VMWare Workstation image when I suddenly hit a wall with this error

No Drives Found
An error has occurred - no valid devices were found on which to create new file systems. Please check your hardware for the cause of this problem.

Now, this isn't the first time I'm installing CentOS on a virtual machine nor on a physical hardware but it definitely is the first time to install version 5.2. Back in the old versions, everything was pretty straight-forward and that I had never encountered this error message before. I was beginning to be tempted to use an iSCSI disk for the installation with another virtualized iSCSI disk but I wouldn't want to go down that road unless I will be configuring this virtual machine as a clustered server. Having searched thru a ton of newsgroup and blog posts on similar issues, a few of them mentioned changing the Operating System to Red Hat Enterprise Linux or Other Linux 2.4.x kernel to make it work. I did find a recommendation to change the virtual disk from SCSI (which happens to be the default setting when you configure your virtual machine) to IDE. That did the trick, although I needed to create a new virtual machine in the process which was the quickest way to do it.

So, remember - use an IDE disk in your VMWare image when installing CentOS 5.2

Tuesday, May 19, 2009

Backup on shared folders running on a local system account?

I still see a lot of SQL Servers running using the LocalSystem account, particularly, MSDE 2000, which is very popular among third-party applications that requires storing data in a database. Others run a stand-alone SQL Server system and use LocalSystem account for the service accounts. While this may be a security risk, a lot of users still have them configured. And when they need to generate database backups on a shared folder, the SQL Server service's attempt to connect to network resources are denied access because they have no credentials and they are using a null session.Of course, a typical recommendation would be to change the service account to a local Windows or a domain account with least privilege but not everybody is open to that suggestion. So how do you allow SQL Server to generate a backup on a shared folder while using a LocalSystem account? The solution: enable null session shares

While I do not advocate such workarounds as it opens up additional security loopholes, it still is a workaround. And as I usuallly say,
WARNING: This is not a recommended approach. Use at your own risk

Microsoft has a documented procedure to enable null sessions shares and while the KB article mentions Windows 2000, it does work for Windows Server 2003. This should be done on the Windows machine that hosts the shared folder. A word of caution if you intend to use this approach - document every step that you do and make sure you rollback any changes made after generating your database backup. Tasks like enabling the Guest user account (this is disabled by default), modifying the registry, etc. should be rolled back as soon as you're done, otherwise, you're opening up security vulnerabilities across your network.