1. acpi-support - You'd better leave it on "X" at S runlevel.
2. acpid - The acpi daemon. These two are for power management, quite important for laptop and desktop computers, so leave them on.
3. alsa - If you use alsa sound subsystem, yes leave it on.
4. alsa-utils - On my system, this service supercedes the alsa, so I turn off the alsa and turn this on at S level. **Note**, I mean "turn off" is to remove all "X" at all runlevels. If you don't have it on your system, no problem. Just keep going.
5. anacron - A cron subsystem that executes any cron jobs not being executed when the time is on. Most likely you've probably turned your computer off when a certain cron job time is ready. For example, updatedb is scheduled at 2am everyday, but at that moment, you computer is off, then if anacron service is on, it will try to catch up that updatedb cron... I turn it off cause it didn't turn my laptop off very offen, but its totally up to you for this one.
6. apmd - This is the one that confused me a quite bit. I have acpid on already and what's the benefits of having apmd on too? If you computer is not that old which can't even support acpi, then you may try to turn this off. I did anyway.
7. atd - like cron, a job scheduler. I turned it off.
8. binfmt-support - Kernel supports other format of binary files. I left it on.
9. bluez-utiles - I turned it off. I don't have any bluetooth devices.
10. bootlogd - Leave it on.
11. cron - Leave it on.
12. cupsys - subsystem to manager your printer. I don't have so I turned it off, but if you do, just leave it on.
13. dbus - Message bus system. Very important, leave it on.
14. dns-clean - Mainly for cleaning up the dns info when using dial-up connection. I don't use dial up, so I turn it off.
15. evms - Enterprise Volumn Management system. I turned it off.
16. fetchmail - A mail receving daemon. I turned it off.
17. gdm - The gnome desktop manager. I turned it off anyway since I get use to boot to console first. This is up to you if you want to boot directly to GUI.
18. gdomap - Actually I have no idea why this one should on. I didn't see any other systems have this daemon, so I turned it off and I don't feel I lose anything. Any benefits to have it on a loptop or desktop?
19. gpm - Mouse support for console. If you feel you'd better have a mouse on console, go turn it on at runlevel 1 and 2. That's all you need.
20. halt - Don't change it.
21. hdparm - tuning harddisk script. I removed the 2, 3, 4, 5 runlevel but add it to S runlevel. I feel that opening DMA, 32bit I/O, etc eariler will benefit the rest of the processes. Also I changed the original script to a very simple one that I made myself. I feel useless to put all those redundant checks if I know what I am doing. The configuration file is /etc/hdparm.conf.
22. hibernate - If your system support hibernate, leave it on. Otherwise, its useless for you.
23. hotkey-setup - This daemon setup some hotkey mappings for Laptop. Manufacturers supported are: HP, Acer, ASUS, Sony, Dell, and IBM. If you have a laptop in those brands, you can leave it on, otherwise, this might not have any benefits for you.
24. hotplug and hotplug-net #activating hotplug subsystems takes time. I'd consider to turn them off. I did some changes in my /etc/network/interfaces file. Instead of mapping my wireless card during hotplug process, I set it up to auto. So I can turn them off. I've tested even I turned them off, ubuntu can still detect my usb driver, my digital camera, etc. So I think its pretty safe to turn them off. **Note** If you find your sound card doesn't work after turning hotplug service off, you can turn it back. Or edit /etc/modules file to add your sound card's driver module. Tested out the later one is faster.
25. hplip - HP printing and Image subsystem. I turned it off.
26. ifrename - network interface rename script. Sounds pretty neat but I turned it off. Mainly for managing multiple network interfaces names. Since I have a wireless card and an ethernet card, they all assigned eth0 and ath0 from kernel, so its not really useful for me.
27. ifupdown and ifupdown-clean - Leave it on. They are network interfaces activation scripts for the boot time.
28. inetd or inetd.real - take a look your /etc/inetd.conf file and comment out any services that you don't need. If there aren't any services there, then it's very safe to turn them off.
29. klogd - Leave it on.
30. linux-restricted-modules-common - You need to see if you really have any restricted modules loaded on your system. Since I need madwifi ath_pci module, so I left it on. The restricted modules can be found from /lib/linux-restricted-modules. If you find that you are not using any of the restricted modules, then its ok to turn it off.
31. lvm - I don't use it so I turned it off. Leave it on if you *DO* have lvm.
32. makedev - Leave it on.
33. mdamd - Raid management tool. I don't use it so I turned it off.
34. module-init-tools - Load extra modules from /etc/modules file. You can investigate your /etc/modules file and see if there is any modules that you don't need. Normally, this is turned on.
35. networking - bring up network interfaces and config dns info during boot time by scaning /etc/network/interfaces file. Leave it on.
36. ntpdate - Sync time with the ubuntu time server. I don't need it on boot time so I turned it off.
37. nvidia-kernel - I compiled the nvidia driver by myself, so its useless for me now. If you use the ubuntu nvidia driver from the restrict modules, just leave it on.
38. pcmciapcmcia - Active pcmcia device. I changed it to start on S runlevel instead of on each 2,3,4,5 cause I feel it's better to have hardware device ready at first. Also, useless if you are using desktop which doesn't have pcmcia card. So in that case, turn it off please.
39. portmap - daemon for managing services like nis, nfs, etc. If your laptop or desktop is a pure client, then turn it off.
40. powernowd - client to manage cpufreq. Mainly for laptops that support CPU speed stepping technology. Normally, you should leave it on if you are configuring a laptop, but for desktop, it might be useless.
41. ppp and ppp-dns - Useless to me. I don't have dial-up.
42. readahead - **Thanks mr_pouit!** It seems readahead is a kind of "preloader". It loads at startup some libs on memory, so that some programs will start faster. But it increases startup time for about 3-4 seconds. So, you can keep it... or not . **update** I tested and I just didn't feel difference loading programs. So I decided to turn it off. If you have a reason to keep it on, please do so.
43. reboot - Don't change it.
44. resolvconfresolvconf - Automatically configuring DNS info according to your network status. I left it on.
45. rmnologin - Remove nologin if it finds it. It wouldn't happen on my laptop, so I got rid of it.
46. rsync - rsync daemon. I don't use it on my laptop, so turned it off.
47. sendsigs - send signals during reboot or shutdown. Leave it as it is.
48. single - Active single user mode. Leave it as it is.
49. ssh - ssh daemon. I need this so I turned it on.
50. stop-bootlogd - stop bootlogd from 2,3,4,5 runlevel. Leave it as it is.
51. sudo - check sudo status. I don't see any good to run it every time on a laptop or desktop client, so I turned it off.
52. sysklogd - Leave it as it is.
53. udev and udev-mab - Userspace dev filesystem. Good stuff, I left them on.
54. umountfs - Leave it as it is.
55. urandom - Random number generator. Might not useful but I left it on.
56. usplash - Well, if you really want to see the nice boot up screen, leave it as it is. I just turned it off anyway. If you want to turn it off, you also need to edit /boot/grub/menu. lst file to comment out the splashimage line and get rid of the splash kernel boot option.
57. vbesave - video card BIOS configuration tool. It's able to save your video card status. I left it on.
58. xorg-common - setup X server ICE socket. I moved it from starting at runlevel S to runlevel 2,3,4,5. Since I don't need this if I boot to single user mode. This way it wouldn't occupy time during the initial booting.
