Nov 112014

GUI based web server management tool Webmin is one of the many blessings of the open source movement.

For those not up to speed on command line tools, there’s nothing like Webmin to manage a Linux server.

A module based application, Webmin lets you set up new web sites, delete old sites, set up e-mail, edit files, make changes to IP table rules, examine your logs and so on.

I’ve used Webmin for several years and found it to be a rock solid, reliable control panel that greatly reduces the complexity of managing a Linux server.

Surely, there are a lot of server administrators like me depending on Webmin to get the job done.

But over the last few months I’ve been extremely frustrated at not being able to open Webmin’s File Manager in the Firefox browser on both Windows and Linux systems. When I clicked on File Manager, it would not open because of issues with the IcedTea browser plugin for running Java applets. I would get an error message and the File Manager wouldn’t open.

Here’s the error message, which I have described below only in part:

net.sourceforge.jnlp.LaunchException: Fatal: Initialization Error: Could not initialize applet. For more information click “more information button”.
at net.sourceforge.jnlp.Launcher.createApplet(
at net.sourceforge.jnlp.Launcher.getApplet(
at net.sourceforge.jnlp.Launcher$
Caused by: net.sourceforge.jnlp.LaunchException: The applet is signed but its manifest specifies Sandbox permissions. This is not yet supported. Try running the applet again, but choose the Sandbox run option.
at net.sourceforge.jnlp.runtime.ManifestAttributesChecker.checkPermissionsAttribute(
at net.sourceforge.jnlp.runtime.ManifestAttributesChecker.checkAll(
at net.sourceforge.jnlp.runtime.JNLPClassLoader.( …..

Endless frustration!

Except for the File Manager part, the other parts of Webmin and Firefox browser worked fine together.

But since the File Manager is crucial for a lot of tasks (particularly for making quick edits to files) I was often vexed.

I struggled for months, managing as best as I could with the command line.

Solution to Webmin-File Manager-Firefox Issue

Finally, after endlessly scouring the web for a fix I found the solution.

If you’re bedevilled with the Webmin File Manager opening issue as I was, here are the steps I followed to fix the problem:

1. Open Icedtea-web control panel in the terminal by typing itweb-settings

2. On the Icedtea-web control panel, click on Certificates on left-side menu

3. Go to drop-down box (you’ll see it to the right of Certificate Type) and select Trusted Certificates.

4. Remove whatever certificates you find in panel (I found three certificates – one for Oracle, second for Webmin developer James Cameron and the last for my server and got rid of all of them)

5. I then clicked Apply and OK (closes the Icedtea-web control panel)

6. I went back to my server’s Webmin and clicked on File Manager

7. A security dialog box appeared. I first unchecked the “Always Trust” box and then clicked the “Run” button. Nothing will happen.

8. I closed the applet and clicked on File Manager again. The security dialog applet opens. Again, I first unchecked the “Always Trust” box. This time,however, I selected the “Sandbox” option on the applet. Voila, in a few seconds the File Manager opened and I could edit any file I wanted to. 🙂

Note: If for some reason you forget to uncheck the the “Always Trust” box in step 7 or 8 then you will have to go back to step 1 and repeat the steps of removing the certificates.

RedHat developers and users deserve credit for outlining the above process on one of the RedHat forums. The developers initially described it as a workaround and intended to build a patch for a permanent fix to the Webmin/File Manager/Firefox issue.

Subsequently, the issue was dismissed as “not a bug” and “more of a local configuration issue.”

Bug or not, go ahead and try the steps I’ve outlined above.

It should fix the issue of opening of File Manager on Webmin via Firefox browser that many of us have been struggling with.

At least, these steps worked fine for me.

Useful Links
Webmin Control Panel

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