Linux System Tuning - Services
Disabling unneeded services
To ensure that my machines run as efficiently and securely as possible, I disable a number of services after each installation. The end result is a system that accepts ssh connections on TCP port 22, and on one or more service ports that are in use by the applications hosted on the platform. To get to this state, I go through and disable numerous services that come enabled by default. Here is the default list of services that are enabled after a CentOS 4.4 installation:$ chkconfig –l | grep on
atd 0:off 1:off 2:off 3:on 4:on 5:on 6:off messagebus 0:off 1:off 2:off 3:on 4:on 5:on 6:off smartd 0:off 1:off 2:on 3:on 4:on 5:on 6:off portmap 0:off 1:off 2:off 3:on 4:on 5:on 6:off sendmail 0:off 1:off 2:on 3:on 4:on 5:on 6:off netfs 0:off 1:off 2:off 3:on 4:on 5:on 6:off cups 0:off 1:off 2:on 3:on 4:on 5:on 6:off irqbalance 0:off 1:off 2:off 3:on 4:on 5:on 6:off rpcgssd 0:off 1:off 2:off 3:on 4:on 5:on 6:off xfs 0:off 1:off 2:on 3:on 4:on 5:on 6:off isdn 0:off 1:off 2:on 3:on 4:on 5:on 6:off autofs 0:off 1:off 2:off 3:on 4:on 5:on 6:off gpm 0:off 1:off 2:on 3:on 4:on 5:on 6:off apmd 0:off 1:off 2:on 3:on 4:on 5:on 6:off crond 0:off 1:off 2:on 3:on 4:on 5:on 6:off acpid 0:off 1:off 2:off 3:on 4:on 5:on 6:off microcode_ctl 0:off 1:off 2:on 3:on 4:on 5:on 6:off pcmcia 0:off 1:off 2:on 3:on 4:on 5:on 6:off cpuspeed 0:off 1:on 2:on 3:on 4:on 5:on 6:off xinetd 0:off 1:off 2:off 3:on 4:on 5:on 6:off rpcidmapd 0:off 1:off 2:off 3:on 4:on 5:on 6:off readahead_early 0:off 1:off 2:off 3:off 4:off 5:on 6:off readahead 0:off 1:off 2:off 3:off 4:off 5:on 6:off sshd 0:off 1:off 2:on 3:on 4:on 5:on 6:off anacron 0:off 1:off 2:on 3:on 4:on 5:on 6:off network 0:off 1:off 2:on 3:on 4:on 5:on 6:off kudzu 0:off 1:off 2:off 3:on 4:on 5:on 6:off syslog 0:off 1:off 2:on 3:on 4:on 5:on 6:off nfslock 0:off 1:off 2:off 3:on 4:on 5:on 6:off rawdevices 0:off 1:off 2:off 3:on 4:on 5:on 6:off mdmonitor 0:off 1:off 2:on 3:on 4:on 5:on 6:off haldaemon 0:off 1:off 2:off 3:on 4:on 5:on 6:off
Several of these services are required, but several others serve no purpose in my environment, and use CPU and memory resources that would be better allocated to my applications. Since I don’t use RPC services, autofs or NFS, those are the first to get disabled:
$ /sbin/chkconfig –level 0123456 portmap off
$ /sbin/chkconfig –level 0123456 nfslock off
$ /sbin/chkconfig –level 0123456 netfs off
$ /sbin/chkconfig –level 0123456 rpcgssd off
$ /sbin/chkconfig –level 0123456 rpcidmapd off
$ /sbin/chkconfig –level 0123456 autofs off
I also don’t allow individual hosts to receive mail from the outside world, so sendmail gets nixed next:
$ /sbin/chkconfig –level 0123456 sendmail off
On server platforms, who needs printing?:
$ /sbin/chkconfig –level 0123456 cups off
Now we get to the font server, isdn capabilities, console mouse and pcmcia support. I don’t use these services on my servers, so they get disabled as well:
$ /sbin/chkconfig –level 0123456 xfs off
$ /sbin/chkconfig –level 0123456 isdn off
$ /sbin/chkconfig –level 0123456 gpm off
$ /sbin/chkconfig –level 0123456 pcmcia off
Once these services are disabled (and optionally stopped with the service command or a reboot), my netstat output looks nice and clean:
$ netstat –tcp –udp –listening
Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 *:ssh *:* LISTEN
This has served me well over the years, since it reduces boot time (less rc scripts to run), and frees up additional resources for my applications (while this isn’t substantial, every page of memory helps!).
