Tips and Tricks

More about Fedora 18

Information Linux Reviews Technical Tips and Tricks

In my review of Fedora 18, I discussed my initial impressions of that newest release. Having now begun to install Fedora 18 on several more hosts in my constantly changing world I have found some interesting under the cover changes.

firewalld

A new firewall, firewalld, is now the default firewall for Fedora. Of course Fedora is the proving ground for many new things so, while this change was not particularly well documented, changes to Fedora in general should not be a surprise. The firewalld daemon is mentioned in three short paragraphs in the Fedora 18 release notes which only references the man pages for the new firewalld commands for further information, and once as being a new addition in the Technical Notes document. Both are available as PDF files from the Fedora Documentation Project.

The firewalld rules are quite complex compared to what I have been using with IPTables. This, and the fact that I am not yet familiar with the rule syntax or the overall structure of firewalld means that, for now at least, I need to revert to IPTables on my Fedora 18 hosts.

Reverting to IPTables

The good news is that the old IPTables firewall is still available until I can learn how to best create the firewall rules I need with firewalld. However it, too, has changed and some of the old IPTables rules, especially those using state related rule sets have been altered.

First, to convert back to IPTables, stop and disable the firewalld service and start and enable the iptables service.  Of course you must do this safely with your network disabled until you can get your new (old) firewall back in place. Then use the iptables-restore command to restore your old IPTables rules from the saved copy. You did save a backup copy of your IPTables firewall rules, right?

At this point, IPTables gives some errors indicating that one should use new connection tracking rules in lieu of the state-related rules. The best part is that IPTables is smart enough to give you the warning message and then translate the rules into connection tracking rules. At that point you can simply use the iptables-save command view the translated rules and redirect the output to /etc/sysconfig/iptables to save the translated rules.

So now I will take some time to learn this new firewall system while my IPTables firewall protects me.

Here is a link to the Fedora Project FirewallD documentation. http://fedoraproject.org/wiki/FirewallD

CDs and DVDs that Won’t Mount

Information Tips and Tricks

Have you ever had a CD/DVD, whether data, video or audio that would not mount or play? Me too.

Fedora Linux (and others) is supposed to recognize that a CD or DVD has been inserted into the drive, and the Device Notifier will pop up a small window that displays “Devices recently plugged in.” This allows you to open the device with Dolphin or some other application.

The Device Notifier window pops up when a new storage device is plugged in or inserted into a drive.

The Device Notifier window pops up when a new storage device is plugged in or inserted into a drive.

Sometimes you can insert a CD or DVD and nothing happens; it is as if the disk does not exist. This can happen if there is a problem with the disk itself or the drive. The most common reason for this problem is dirt or dust, although scratches can cause problems like this, too.

If the DVD drive is one that exposes the read/write head when it is open, such as the very thin ones used in laptops, you can clean the DVD drive read optics with a very soft camel hair brush, or use a can of compressed air to blow the dirt off the lens. Drive cleaning CDs can be used on other types of DVD drives. The other thing you can do is clean the bottom surface (the surface without the printing on it) of the CD or DVD with a soft, dry cotton cloth. Rubbing it on a clean cotton tee-shirt works well.