This may be old news, but, here's how I did it -
I'm running Slackware 11.0 with Dropline Gnome 2.16.1 Kernel is the huge26.s (2.6.17.13). I'm also using the Nvidia 1.0-9639 driver.
One caveat: No one to my knowledge has been able to get Wine and Linux to look for the applicable CD when starting up the game (and I tried with 2 different Wine versions for 2 days). So, you have to find and download the no-cd rts.dll file(s) to make the game play under Linux.
Here's How I did it
Setup your Cdrom for automounting in /etc/fstab. In the options column, you should have the following: auto,users,ro
Install WINE. I recommend a fairly recent version. I'm using WINE-0.9.44
run winecfg and setup your wine configuration as follows:
Under the "Applications" tab, select "WindowsXP" for Windows Version
Under the "Drives" tab, setup your drives. The C:\ drive is normally mapped to /home/<username>/.wine/drive_c
Take note of what drive letter your cdrom is mapped to. This is important for installation disc changing. Mine was F:. If your cdrom isn't listed, click on "autodetect" and it should show up.
Under the "Audio" tab, I checked the ALSA driver, unchecked the OSS driver, and set the Direct Sound Hardware Acceleration to "Emulation".
Make sure you click on "apply" and/or "Ok" before exiting winecfg.
Open up terminal and type the following: ln -s /dev/input/js0 /dev/js0. Wine has a habit of looking for the joystick in /dev instead of /dev/input.
Install Forgotten Battles as follows:
insert disc 1
open a terminal and type "wine <your cdrom letter>:\setup.exe" without the quotes. I typed "wine F:\setup.exe". FB should start installing - follow the prompts.
Around 64% completion, you'll get the "please insert disc 2" message. Open another terminal and type "wine eject F:" (or whatever your cdrom drive letter is).
Insert the 2nd disc and wait for it to automount. Once it does, click on "retry". Follow the prompts. Do not install DirectX8.1.
You may or may not get a message about the Ubi.com installation being aborted because the installer could not find IE4. Click OK and don't worry.
If you plan to install the Ace Expansion Pack, skip to Step 5, otherwise, proceed as follows -
Install the version 1.22 patch as follows - "wine path/to/il2_fb_v1.0_to_v1.22.exe". I had put my patches in /home/user/ubisoft/fb. So, I typed "wine ubisoft/fb/il2_fb_v1.0_to_v1.22.exe". Follow the prompts. The winzip extractor should be setup to extract to the mapped C:\Program Files\Ubi Soft\IL-2 Sturmovik Forgotten Battles folder.
Now copy the no-cd rts.dll file into the IL-2 Sturmovik Forgotten Battles folder. I also place a copy in the Ubi Soft folder.
Install AEP as follows:
open a terminal and type "wine regedit". You'll see a Windows registry. Navigate to [HKEY_LOCAL_MACHINE\SOFTWARE\Ubi Soft\IL-2 Sturmovik Forgotten Battles]. You'll need to make or ensure the following string value is present - string name = language; string value = en_us.
Pop the AEP cd in, and, once it mounts, open a terminal and type "wine <your cdrom letter>:\setup.exe".
The rest of the procedure is the same as above in steps 4.6 to 4.8. Do not patch if you're going to perform a merged Pacific Fighters install (next).
Install Pacific Fighters (merged) as follows:
Insert the 1st disc, open a terminal, and type "wine <your cdrom letter>:\setuppffbaep.exe".
Once again, you'll get the "please insert disc 2" message at the appropriate time. Open another terminal and type "wine eject F:" (or whatever your cdrom drive letter is).
Insert the 2nd disc and wait for it to automount. Once it does, click on "retry". Follow the prompts.
Now, install the PF patches in the same manner as above in step 4.7. For each patch, you'll get a popup asking something about installing Gecko. Just click cancel and continue.
Once you've completed patching, its time to copy the no-cd rts.dll file into the IL-2 Sturmovik Forgotten Battles and the Ubi Soft folders.

thanks for the infor!