In the following tutorial you are going to fine tweak your Ubuntu Linux setup in order to speed up the boot process as well as the startup time of some frequently used applications.

1. use bootchart to profile boot times and bootlenecks easily through an intuitive image graph
   install with

   sudo apt-get install bootchart
   
   then you’ll get a graph in /var/log/bootchart directory each time you boot your system.
   charts will be looking like the image on the right (click to zoom)
   

2. utility to tweak services startup
   refer to post Managing startup services
   Comments on what some services actually are meant to can be found here http://ubuntuforums.org/showthread.php?t=89491.
   Be careful in disabling services since many despite not being necessary provide indeed useful features!
3. (11 seconds save!) disable sl-modem-daemon startup service. This service is indeed buggy! Recent version provided with Ubuntu Intrepid has this  issue fixed.
4. (7 seconds save!) vmware-networking in vmware workstation 6.5 and 6.5.1 lags at boot time.
5. remove a few tty. By default there are F1 through F7, we do not need all seven: in folder /etc/event.d/ comment out all entries in tty4 tty5 files. Three vts should be enough.
6. Profile your boot.
   When you have the Grub menu to start your system, hit the “e” for edit the kernel line you normally start with. Then move to the end of the Kernel line and edit quiet splash to quiet splash profile. Don’t save this line just let it boot up “b” once with this profile parameter.
   This boot will go very slow because it is profiling (read putting all read disk blocks behind each other) the normal boot to optimize performance. All subsequent boots will then go faster. If all boots go very slow afterwards make sure that the profile parameter was not saved as a boot option.
7. Configure readahead to preload files needed in your dektop environment while waiting for the username and password prompt. The more RAM you have the more you can preload. 512 is really the minimum.In /etc/readahead you can find the lists of preloaded files for the boot sequence (we have customized this in the previous step). Now we are going to create a profile of our desktop.
   At the login prompt, now change vts with CTRL+ALT+F1, login and write down
   
   sudo readahead-watch -o /etc/readahead/gnome /

   This will grind the disk for a while then it will return you to a command prompt. The profiler is now in the background watching all actions. Now, without logging out, go to your destop login prompt (ALT+F8 ) and log in normally. After you are fully logged in, press CTRL+ALT+F1 to go back to your terminal, and stop the profiler with
   
   sudo killall readahead-watch
   
   We would have to prune the resulting list a bit as Jdong suggests: In a terminal, run:

   cat /etc/readahead/gnome | xargs -i ls -lk {} | sort -rn -k +5 | less

   This will display all the files readahead wants to cache, sorted by largest file first. The 5th column (before date) is the size of the file in KB. Make sure there’s nothing too large. If it’s bigger than 10,000KB or so, it’s probably not worth preloading. You can remove unwanted files from the preload list by opening /etc/readahead/gnome in your favorite editor, and deleting its line.

   NOTE: If you have your home on a different partition, you should repeat the previous steps for each partition, replacing ‘gnome’ filename with a different name and the mountpoint / with each interested mountpoint.

   To make your linux box apply this trick at every boot edit file /etc/rc.local and add in the line preceding ‘exit 0′:
   for list in /etc/readahead/*; do
   readahead-list $list
   done

   credits and reference: http://ubuntuforums.org/showthread.php?t=565651

8. (2 seconds save!) check the sixth column in file /etc/fstab set 0 for devices that do not need to be checked regularly
   set 1 only for root /
   set 2 for other partitionsThis is the standard, however you could have wrongly edited fstab file. This setup ensures only root filesystem is quickly checked at boot time, thus saving a little time excluding other filesystems when not necessary (these will be checked only after a dirty shutdown or on a scheduled basis).
9. (6 seconds save!) Enable concurrent booting allows Ubuntu to take full advantage of dual-core processors, as well as processors that hyperthread or multithread.
   NOTE: this doesn’t seem to work for me. It messes up GNOME loading, probably due to an unsolved race condition. However, if you manage to have it notably improves your boot loading time.These settings are located in your /etc/init.d/rc file.
   sudo gedit /etc/init.d/rc
   Look for CONCURRENCY=none and change it to:
   CONCURRENCY=shell

   race conditions problems with dbus hal and gdm exhist
   http://ubuntuforums.org/showthread.php?t=574992
   https://bugs.launchpad.net/ubuntu/+source/hal/+bug/149881

10. I have read a lot about using prelink program. This is intended to prelink binaries to libraries only once in a while instead of each time the executable is launched. This should save some time. However I have also read that prelink is no longer needed in recent Ubuntu versions.
    You can install prelink via
    
    sudo apt-get install prelink
    
    then run it the first time with
    prelink -mR
    and edit file /etc/defaults/prelink and change “PRELINKING=unknown from “unknown” to “yes”

    reference with performance benchmarks here
    http://www.quintinriis.com
    http://ubuntuforums.org/showthread.php?t=1971
    http://ubuntuforums.org/showthread.php?t=74197
    

11. Figure out SWAP problems.
    Indeed swap has a high impact over our system performance, however I am not going to focus on swap usage here, but on swap misconfiguration. This can lead to a 10 seconds delay in the startup / boot process.Symptoms: Splash screen freezes after about 10 seconds of normal boot and stays this way for about a minute or so and never resumes (all text mode boot after). The boot process is stuck for 10 seconds after launching local-premount scripts with following message:
    Begin: Waiting for resume deviceThis behavior is caused by the fact that you have somehow modified your swap partition (new linux setup? new hard disk? swap partition resize?) and thus initramfs-tools cannot find the partition through the old UUID.

    first make the swap partition work again by
    sudo mkswap /dev/sda9
    (where sda9 should be the corresponding partition on your system. Check gparted to ensure this. This will DESTROY all your data if you use it on a data partition, like your /home one)

    then compute the UUID of the new swap partition
    sudo blkid /dev/sda9

    change the UUID code in both these files
    /etc/fstab
    (only change the one concerning /dev/sda9!)
    /etc/initramfs-tools/conf.d/resume

    rebuild the initramfs with
    update-initramfs -u

    You can also change back the swap UUID with this command
    mkswap -U UUID /dev/swapdev
    where UUID is the ID shown in both mentioned /etc files (the ID should be the same in both them, otherwise follow the 1-3 steps!)

12. Disabling in BIOS USB Legacy Support lets you gain ~8 sec. that the system usually spends probing USB 1.1 legacy devices.

OPTIMIZATIONS NOT RELATED TO STARTUP

1. Enable Firefox pipelining
   type about:config in Firefox’s address bar.
   Type pipelining in the filter text box. This will leave three options on screen.
   Double-click network.http.pipelining to turn its value from false to true.
   Do the same for network.http.proxy.pipelining
   Double-click on network.http.pipelining.maxrequests and change “4” to “6.” (do not increase this value beyond)
   Finally, on any blank space in the browser window, right-click and choose New>Integer
   When prompted for a name, type nglayout.initialpaint.delay and set its value to 0.
2. Remove unnecessary font packages:
   in a terminal issue the command:

   dpkg -l | grep ii| awk '{print $2}' | grep ttf

   your output would be probably far too long. You may safely remove all packages except for the following ones: ttf-bitstream-vera, ttf-dejavu, ttf-dejavu-core, ttf-dejavu-extra, ttf-freefont, ttf-opensymbol AND those of the languages you actually use on your system (check each package language searching for it with Synaptic package manager).
   All the other ones can be safely removed.

3. Enable Ethernet network offloading
   click here for the howto
   
4. Consider removing mono framework. sudo apt-get –purge remove libmono0
   NOTE: this would remove also some default applications such as Tomboy (replace it with ZIM or Basket Note Pads), and F-Spot (replace it with gThumb)
5. Preload is an “adaptive readahead daemon” that runs in the background of your system, and observes what programs you use most often, caching them in order to speed up application load time. By using Preload, you can put unused RAM to good work, and improve the overall performance of your desktop system.
   This does not waste much RAM, and does not either improve boot up speed, it only acts for applications started after the boot up process.
   use sudo apt-get install preload to install it,
   use sudo apt-get install ld.so.preload-manager to install a program useful to manage the preloaded ones.

   reference: http://www.techthrob.com/tech/preload.php