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I will relate a recent battle I had with a laptop that uses the Prism54 wireless chipset and runs Fedora 10. For quite some time, I could not get it to connect to a WPA protected network. With an open network, it would connect just fine. I didn’t bother with WEP. I wanted to find out what was causing it to fail with WPA.

This is an older eRacks CENTRINO laptop (Pentium M 1.6ghz, 1GB RAM and an 80GB hard drive.) This post will also hopefully help anyone else who has a laptop with the Prism54 chipset (mine specifically is a PrismGT mini-pci card.) Note that Prism54 is also available in PCI and USB wireless devices.

At first, I thought it might be a problem with the GNOME NetworkManager.  So, I tried other methods of connecting, such as using the command line (for iwconfig/ifconfig), wicd, Wireless Assistant and WiFi Radar. Some of these seem to work better than others, but again, none would allow me to connect to my WPA protected network at home. Thus, it was time to dig deeper.

After some sifting through forum posts, blogs, and bugzilla, I finally came across something that might help. Apparently, the prism54 drivers have several different modules that are loaded. For some reason, there is a module (prism54), which might be an older version of the complete set, and then there are other separate ones: p54common, p54pci and p54usb. So in my case, it was loading prism54, p54common, and p54pci. According to what I have read, the prism54 module causes conflicts with the newer p54common and p54pci set. The suggestion for now is to add prism54 to the module blacklist, located in /etc/modprobe.d/blacklist. You add the following entry at the bottom:

blacklist prism54

Once I did this and restarted networking, I could connect to my WPA-protected network using the default GNOME NetworkManager. All is well again in WiFi land.

Hopefully, this little jaunt with prism54 will be able to help someone else.

March 13th, 2009

Posted In: How-To, Laptop cookbooks

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This article is geared toward eRacks customers who have a desktop or laptop system, i.e. a personal workstation.  It is not intended to serve as a guide for customers wishing to upgrade a server.

With the above in mind, for those who use Linux on  such a machine, your choice of distributions that cater to this niche is growing nicely.  You have the “Big Boys” such as Ubuntu, Fedora, Mandriva or OpenSUSE, as well as a host of more specialized distributions, the main focus of most being on user friendliness and “up-to-dateness.”  What this usually leads to is a faster upgrade cycle than what you would typically find on a server oriented distro such as Debian (stable), RedHat Enterprise, SuSE Enterprise or CentOS.

I myself have been tracking RedHat (including Fedora) since version 5.0, doing a mix of upgrades and fresh installs.  I have also kept up with Ubuntu since 6.04, and have had similar experiences with it.  I have found that one way of making regular upgrades easier is to keep a separate /home partition.  This way, you have a choice of an upgrade or a fresh install, without losing valuable data.

My experience, and that of many other salty seasoned Linux gurus, is that upgrading from a previous version tends to be a bit messier and usually takes longer to do than a fresh install.  This can be true, especially if you use third party repositories, if you install software not maintained by your distro package manager (DEB or RPM) or if you do a lot of tweaking.  Doing so may leave you looking at a broken system when the upgrade finishes.  For this reason, it is usually more desirable to do a clean installation and install your third party applications afterward.

How then to keep from losing your data?  Many system admins would suggest the multiple partition method, which has been used on servers a lot, yet not so much on the desktop.  The multiple partition method can have advantages and disadvantages, but since hard drives are so big these days, many of the disadvantages are no longer prevalent.

While most modern desktop distros have a default partitioning scheme that gives you just a swap partition (usually about 2x the amount of RAM, or physical memory) and a large root partition for everything else, most server configurations have multiple partitions for directories like /usr or /var, which can have many advantages.  For example: if you wanted to have /usr mounted as read-only to prevent unauthorized system-wide software installs, if you wanted to keep /boot separate for a RAID array or if you wanted to keep /var and /tmp separate to avoid corrupting the core system files; these are all examples of why one might want to make use of multiple partitions.  In this case, however, the partitioning must be very carefully planned according to the intended use of the server, what programs need to be installed, how many users will be logging in, etc.

Luckily, there is a happy medium that works well for desktops, and that is to use a swap partition with 2x the amount of RAM, a root partition for your operating system and a very large /home partition for all your data.  When you do a fresh install, all you have to do is make sure you don’t format /home, and your data will be safe across installations.  If you want to save any system-wide tweaks, you will, of course, also have to backup important configuration files and check them against their replacements, making changes where necessary.

In my case, I have a 120GB hard drive for Linux, which makes use of the following partition scheme:
20GB /
75GB /home
1GB /swap
14GB “other” (at times it has a Gentoo install, other times it has FreeBSD, depends on my mood…)

I have found through experience that this setup works well.

When I do an OS update, such as my recent one to Fedora 9, I usually backup important configuration files to /home, do a fresh install and finally install any third party programs I need.

In the past, when upgrading systems without doing a fresh install, things for me have tended to get rather wonky.  However, I have recently tried upgrading Ubuntu, and I must say that the recently improved Upgrade Manager, a graphical front end to the apt-get dist-upgrade functionality, is a nice touch.  It allows you to upgrade to the next version of Ubuntu, while still allowing you to run your system so you can go about your business as it downloads and installs all the packages.  When it’s done, you simply reboot, and voila, new version!  Upgrades on Fedora, by contrast, are still usually done by the tried and true method of booting the install disk and running the upgrade procedure.  Fedora does have the capability to do upgrades using the yum package manager, but that functionality isn’t as mature as apt-get dist-upgrade, and thus is not for the faint of heart.

So now, what if you have an existing Linux installation utilizing only a single partition and you want to do a fresh install while keeping your data safe?

Of course, you could just back your data up to a large external hard drive, but not everyone has one at their disposal.  In this case, what you could try is resizing your root partition, create a new partition for /home and copy your personal data to it before starting the upgrade.  Then, just run through the installation as usual.  This is, of course, only if you have enough space to resize.  If not, you may still require an external drive, at least temporarily, to copy your data to before starting the installer.

If you want to make use of multiple partitions on a new eRacks system purchase, just ask for it during your order.  This way, your system will be ready when the next OS update rolls around!

Matt

June 27th, 2008

Posted In: How-To, Laptop cookbooks, Upgrades

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