450 CHAPTER 31 OPTIMIZING YOUR SYSTEM Table
450 CHAPTER 31 OPTIMIZING YOUR SYSTEM Table 31-1. Ubuntu Run Level Services (Continued) Service Description hotplug-n[et] hplip ifrename ifupdown ifupdown-[clean] klogd linux-res[trictedmodules-common] lvm makedev mdadm mdadm-raid module-in[it-tools] mountvirt[fs] networking ntpdate pcmcia powernowd ppp pppd-dns readahead Works like hotplug. Don t disable it. Subsystem for Hewlett Packard (HP) scanners and/or printers. If you don t use an HP scanner or printer, you can disable this. Part of the networking subsystem that allows the renaming of network devices. Unless you re running a complicated server system, this can be safely disabled. If you find your network connection doesn t work afterwards, enable it. Part of the network subsystem. Don t disable it. Part of the network subsystem. Don t disable it. Logs kernel messages. This is handy for problem solving, but this service can be disabled if you re absolutely sure you ll never need it. Handles the loading of closed-source kernel modules, such as some wireless card and graphics card drivers. Unless you re sure you don t use such drivers, don t disable this service. Controls the Logical Volume Management (LVM) subsystem. If your system doesn t use RAID or any other kind of LVM system, this service can be disabled. Controls the /dev hardware subsystem. Don t disable it. Controls the software RAID setup. Disable it if you don t use software RAID. Controls the software RAID setup. Disable it if you don t use software RAID. Loads additional kernel module(s). Don t disable it. Mounts virtual file systems that are essential to Ubuntu. Don t disable it. Manages network interfaces. Don t disable it. Synchronizes time with the Ubuntu time servers. You can disable this, unless your PC s system clock is faulty and loses/gains time. Starts PCMCIA devices on notebooks. You can disable this if you use a desktop computer, unless you have a PCI-based wireless card (or similar) that uses a PCMCIA card. Controls the CPU frequency scaling service that s common on many notebook and desktop computers. This can be disabled if absolutely necessary, but it s a good thing to have around. Controls PPP connections, such as those established by modems (both dial-up and DSL/cable). If you don t use a modem, you can disable this. Controls PPP connections. You can disable it if you don t use a modem. Optimization software designed to store commonly used libraries in memory. It s designed to speed up your system, but many people report it makes little difference, so it can be disabled.