There was a day when Oracle was small enough that a DBA could install it from the command line. There were only a few pieces and the flow and dependencies could be established. After all, the first PC version, version four, came on six 5 1/4″, 360 KB floppies. Six disks… and the sixth contained the employee database still available today.

So I will not say that Oracle cannot be installed from the command line. I am sure there is someone who has; however, it is not an everyday occurrence. The Oracle installer is for all practical purposes, required. And that means using Xwindows when running any flavor of Linux or Unix.

I could not live without Google, well, search, as a Microsoft Partner, I use Bing as my default page and search engine. All of the answers are pretty much out there. The truly new issues, not so much. They may require My Oracle Support (MOS) to resolve. Those become a competition to see who can resolve first… so those should be blogged, for sure. The real easy answers, perhaps nothing more than a thank you.

X11 deserves a post. There are several pieces that are needed under different circumstances. Not all of them are always needed always, and while some work, some also cause other problems. There is always the incentive to accept default values. The more defaults, the easier the debugging process.

Working from a Windows laptop using an Amazon Virtual Private Cloud to a server behind a NAT (firewall) with the target host being on a private subnet, X11 needed to be displayed back on my laptop.

The Windows PC must run an X server to receive these “forwarded” displays. We are using a free version of Xming. Support is available with a paid version. The documentation is pretty cryptic. puTTY is installed and configured, as well.

Linux hosts files are set in the NAT and the target host. The sshd configuration files on both hosts have non-default values for X11forwarding (equal yes). There are other things to check in an active environment. We have removed Amazon’s default users, added new groups and users, configured security, restricted others, and disabled root SSH login. But, as for default X11 value changes, X11forwarding is the only one.

X11 packages were installed after the servers were built. SSH has been configured with private keys on the hosts, too. That means the Open Client modules were installed, too. An issue arose behind the NAT when SSHing to the new server. The error message indicated it was a “DISPLAY” problem.

Both error messages pointed to a “bad display name”. One might spend hours trying to determine the proper way to set it. In the end, the proper thing to do is to “unset DISPLAY”, yes, unset it.

More careful Googling of the message, which was reported by xauth, one finds that the real reason for the message was that xauth was not installed on the target host. After installing xauth on the target host, xclock displayed back on the laptop. We love magic cookies.

xhost + was mentioned in several posts, so let me say, when using X11, Xming and xauth, xhost is not required to be used. Don’t forget, unset the DISPLAY variable.

If you are reading this, the chances are you got here through a search. Welcome. I hope the content was exactly what you needed to solve your problem. Hope to see you back here in the future.

Good luck with Xwindows!

– David

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