Moving from Windows to Linux
From MozillaZine Knowledge Base
This article is written for users who are moving from Windows to Linux and want to continue to use Mozilla applications. It can be used with any Linux distribution or window manager, but is somewhat Ubuntu-centric due to that distribution's popularity.
Most Linux distributions have a package manager that supports Thunderbird and Firefox. Many distributions also provide packages for other Mozilla projects (SeaMonkey, Sunbird, ...). If you're using Ubuntu for example, you can use Synaptic to install it if it's not already installed. There is no need to use Automatrix or apt-get. This is the easiest and safest way to install the application, and will meet most users needs.
The tradeoff is that many Linux distributions only release updates for security fixes, since many companies don't want things to change. To help keep things stable, they will frequently disable Help -> Check for Updates, forcing you to wait for the next release of the Linux distribution for any new functionality.
How much of an impact this has depends upon the application. Mozilla strongly recommends you always update all of their applications (regardless of why a new version was released). However, most security updates for Thunderbird are for low priority issues that aren't a problem if you use common sense, while Firefox tends to have more serious security issues. This seems to explain why Ubuntu frequently releases updates whenever a new version of Firefox is available, but doesn't do so for Thunderbird.
Moving your profile data
If the application doesn't start, type locate run-mozilla.sh in a terminal. It should return the directories that have that file, which also contain either the "firefox" or "thunderbird" shell scripts used to start the application. Type echo $PATH into a terminal and verify the directory is on the path.
If it starts but doesn't work correctly, try running in safe mode to temporarily disable any added extensions. While they normally also work under Linux you occasionally run into Gnome or KDE integration problems, or it might not be using a relative pathname to store its data. Exiting the application and deleting the extensions.rdf file in the profile also solves many problems (it will be recreated when you run the application).
You could have also used one of the other methods described in moving your profile to tell Firefox and Thunderbird where to look for the profile. For example, you might want to create a "profiles" directory that contains both your Firefox and Thunderbird profiles.
The Help -> Check for Updates menu is enabled in the build on the Mozilla web site, but it's frequently disabled (though you can still check for updates for add-ons) if you installed it using a package manager with a graphical front end such as Synaptic or Adept. Typically the package manager will check for updates once a day, and ask if you want to upgrade if it finds one.
Ubuntu installs an Alltray program to "dock any application with no native tray icon (like Evolution, Thunderbird, Terminals) into the system tray". If you don't get a new mail icon in the system tray try either installing it or the Mozilla New Mail Icon (Biff) extension.
The menus are different under Linux. Tools -> Options and Tools -> Account Settings are replaced by Edit -> Preferences and Edit -> Account Settings. Additional command line arguments are supported under Linux.
Not all of the fonts that you're used to are available. You may want to install the Microsoft TrueType Fonts. With Ubuntu (or any Debian based distribution) you can use either the package manager or Automatrix to install the msttcorefonts package . For other distributions (Fedora, openSUSE etc.) you could install the rpm's from this web site if you can't find a more convenient solution.
Using a package manager
Debian distributes rebranded versions of Firefox (Iceweasel) and Thunderbird (Icedove). Packages for testing/sarge and unstable/sid users are available in the standard Debian repository. You can fetch and install them using apt-get. You need root access to use it. Type
That will prompt you for the root password. Then update your apt repository.
and fetch/install the desired application.
apt-get install mozilla-firefox
apt-get install mozilla-thunderbird
Install it from a root prompt using Emerge.
will prompt you for the root password. Then fetch/install the desired application using:
You can use firefox-bin and thunderbird-bin instead to install the official binary build. If you run into problems you may need to resync using emerge --sync .
Configure urpmi on your system, using the instructions at easyurpmi. Then use System/Configuration/Packaging/Install Software in the Mandriva Control Center and search for firefox or thunderbird. You could also just type the following from the root in a console:
The applications should be listed in the menu.
The easiest way to install Mozilla applications is through YaST, the SUSE/openSUSE package manager (you have other options with the 10.2+ versions). Those RPM software packages are customized versions of the regular releases. You will have to decide which repository to use:
To install or update Mozilla applications from those repositories:
To update, run YaST Online Update for the regular repositories. For the openSUSE Build Service repository, repeat the sequence above and change the Lock symbol to the "Z"-like symbol for updating this package.
Firefox and Thunderbird are installed by default under both RHEL and Fedora. You can install an updated version from a root account in a terminal:
su yum update firefox
su yum update thunderbird
If you want to use packages from the Fedora Development repository (used to test new releases, so it could break other packages):
su yum -y --enablerepo=development update firefox
su yum -y --enablerepo=development update thunderbird
Use either the Synaptic (Gnome) or Adept (KDE) package manager to install the application depending upon which type of Ubuntu you're running.
For example, select Applications, System, Synaptic Package Manager and enter your password at the prompt. Press the Search button and enter firefox (or thunderbird). Scroll through the list and find the firefox package. Click on the box to the left of it, selecting "Mark for installation". Then press the Apply button. This will install the firefox package plus several other packages it requires.
This should add the application to the menu. You could also add it to the panel (the equivalent of a windows shortcut), or run it from the terminal.
If later on you ever get confused whether you're running a Ubuntu or a Mozilla build run the following from a terminal:
Builds from Mozilla.org look in ~/.thunderbird for the profile while builds from the Ubuntu repository (Synaptic, Adept, apt-get) look in ~/.mozilla-thunderbird.
Using a build from the Mozilla web site
If you don't want to use a build provided by the package manager you can download and install a release from the Mozilla web site. It has the latest release, and doesn't disable automatically checking for updates. You also avoid the risk of a third party build adding code from the trunk (code that is not ready for use by everybody yet) without you knowing about it like Ubuntu sometimes does.
The following instructions are written for Firefox but also apply to Thunderbird, SeaMonkey, Sunbird, etc.
tar zxf firefox-<version>.tar.gz
or (for Firefox 3.0 and above, and mutatis mutandis for Thunderbird 3.x, SeaMonkey 2.x, Sunbird 1.x, ...)
tar -jxf firefox-<version>.tar.bz2
su <password> mv firefox /usr/local chown -R root:root /usr/local/firefox
Step by step example using Thunderbird 18.104.22.168 for Ubuntu
This example doesn't use the default profile location in order to make it easier to troubleshoot. It uses the Mozilla build for Ubuntu, not the Ubuntu third party build.
and verify Thunderbird runs. It should start the new account wizard. Abort and exit Thunderbird.
[General] StartWithLastProfile=1 [Profile0] Name=Tanstaafl IsRelative=0 Path=/home/eric/Profiles/Thunderbird/tanstaafl
Note: The exact name and location of the icons depends upon the version. With Thunderbird 3.0 its a default*.png file in thunderbird/chrome/icons/default/ . However, its always a image file whose name mentions "icon" in a icons subdirectory.
You can get a copy of Firefox and Thunderbird from many sources. Typically (especially if they're part of a Linux distribution) they will identify themselves as Mozilla builds in the help menu, but they may not be identical. They may be a trunk build for the next release, and identify themselves as that version even though Mozilla hasn't released it yet. Or the location its installed in may be modified.
Swiftfox is an optimized build of Firefox. It installs it in the /opt directory. SwiftWeasel has optimized builds for Firefox (Swiftweasel) and Thunderbird (Swiftdove) that are frequently released within a couple of days of a Mozilla release.  The Community Builds/Binaries forums has other 3rd party builds.
Automatrix will install Thunderbird and Firefox using apt-get calls to the Ubuntu repositories, but doesn't provide any update mechanism. Since it's essentially duplicating what you can do with Synaptic, but Synaptic doesn't know the package is installed, you're better off using the package manager.
Ubuntuzilla is a python script that can install 32bit or 64bit builds of Firefox, Thunderbird and/or SeaMonkey under Ubuntu. It provides an option for it to check for updates and notify you. However, the popup is only displayed for a few seconds so you may need to use a checkforupdatetext command if you're unsure whether a update is available.
Synaptic installs Firefox/Thunderbird in /usr/share. Ubuntuzilla installs the programs in /opt and changes the links to run its version by default. It stores the Thunderbird profile in ~/.thunderbird rather than ~/.mozilla-thunderbird. You could change the launcher to use the "mozilla-thunderbird" command instead of "thunderbird" if you want to use the one from the Ubuntu repository. While popular, it has a history of causing problems with the Ubuntu version. Its recommended you choose one or the other, not both.
Many distributions try to make somebody migrating from Windows more comfortable by hiding many of the differences. A few that you might run into when troubleshooting Firefox or Thunderbird are:
If you install the Lightning extension from mozilla.org (rather than one provided by your Linux distro) you probably need to also install "libstdc++5" before installing Lightning since most Linux distributions provide "libstdc++6", which is incompatible with Lightning. See Lightning system requirements for more information.
user_pref("mail.server.server1.directory", "C:\\Users\\eric\\Profiles\\Thunderbird\\tanstaafl\\Mail\\Local Folders");
user_pref("mail.server.server1.directory-rel", "[ProfD]Mail/Local Folders");
The system requirements state that Thunderbird will not run without the following libraries or packages:
and recommends you also have:
Starting with Thunderbird 12.0 libcanberra will be used rather than esound for sounds. 
Most distributions also have their own forums.