IBM REDP-4285-00 User Manual
Chapter 4. Tuning the operating system
97
Draft Document for Review May 4, 2007 11:35 am
4285ch04.fm
In addition, make sure that the default pam configuration file (/etc/pam.d/system-auth for
Red Hat Enterprise Linux, /etc/pam.d/common-session for SUSE Linux Enterprise Server)
has the following entry:
Red Hat Enterprise Linux, /etc/pam.d/common-session for SUSE Linux Enterprise Server)
has the following entry:
session required pam_limits.so
This entry is required so that the system can enforce these limits.
For the complete syntax of the ulimit command, issue:
ulimit -?
4.2.3 Minimize resource use
Systems that are designed for highest levels of performance must minimize any wasting of
resources. We understand that a race car will not offer the same amenities as a normal
passenger car does but for the purpose of driving as fast as possible cup holders and
comfortable seats are a waste of resources. The very same concept also holds true for server
systems. Running a memory consuming GUI and a vast amount of unnecessary daemons
will also decrease overall performance. This section will hence cover the optimization of
system resource consumption.
resources. We understand that a race car will not offer the same amenities as a normal
passenger car does but for the purpose of driving as fast as possible cup holders and
comfortable seats are a waste of resources. The very same concept also holds true for server
systems. Running a memory consuming GUI and a vast amount of unnecessary daemons
will also decrease overall performance. This section will hence cover the optimization of
system resource consumption.
Daemons
After a default installation of Linux distributions, several possibly unnecessary services and
daemons might be enabled. Disabling unneeded daemons reduces the overall memory
footprint of the system, reduces the amount of running processes and hence context switches
and, more important, reduces exposure to various security threats. Disabling unneeded
daemons additionally decreases startup time of the server.
daemons might be enabled. Disabling unneeded daemons reduces the overall memory
footprint of the system, reduces the amount of running processes and hence context switches
and, more important, reduces exposure to various security threats. Disabling unneeded
daemons additionally decreases startup time of the server.
By default, several daemons that have been started can be stopped and disabled safely on
most systems. Table 4-2 lists the daemons that are started in various Linux installations. You
should consider disabling these in your environment if applicable. Note that the table lists the
respective daemons for several commercially available Linux distributions. The exact number
of running daemons might differ from your specific Linux installation. For a more detailed
explanation of these daemons, refer to the system-config-services shown in Figure 4-1 on
page 99 or the YaST GUI as displayed in Figure 4-2 on page 100.
most systems. Table 4-2 lists the daemons that are started in various Linux installations. You
should consider disabling these in your environment if applicable. Note that the table lists the
respective daemons for several commercially available Linux distributions. The exact number
of running daemons might differ from your specific Linux installation. For a more detailed
explanation of these daemons, refer to the system-config-services shown in Figure 4-1 on
page 99 or the YaST GUI as displayed in Figure 4-2 on page 100.
Table 4-2 Tunable daemons started on a default installation
Daemons
Description
apmd
Advanced power management daemon. apmd will most likely not be used on a server.
arptables_jf
User space program for the arptables network filter. Unless you plan to use arptables,
you can safely disable this daemon.
you can safely disable this daemon.
autofs
Automatically mounts file systems on demand (for example, mounts a CD-ROM
automatically). On server systems, file systems rarely have to be mounted
automatically.
automatically). On server systems, file systems rarely have to be mounted
automatically.
cpuspeed
Daemon to dynamically adjust the frequency of the CPU. In a server environment, this
daemon is recommended off.
daemon is recommended off.
cups
Common UNIX Printing System. If you plan to provide print services with your server,
do not disable this service.
do not disable this service.
gpm
Mouse server for the text console. Do not disable if you want mouse support for the
local text console.
local text console.