Red Hat ENTERPRISE LINUX 5 - VIRTUAL SERVER ADMINISTRATION, Руководство по развертыванию

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Updating Packages
601
Note
In general, rebooting the system is the surest way to ensure that the latest version of
a software package is used; however, this option is not always available to the system
administrator.
Applications
User-space applications are any programs that can be initiated by a system user. Typically, such
applications are used only when a user, script, or automated task utility launches them and they
do not persist for long periods of time.
Once such a user-space application is updated, halt any instances of the application on the
system and launch the program again to use the updated version.
Kernel
The kernel is the core software component for the Red Hat Enterprise Linux operating system. It
manages access to memory, the processor, and peripherals as well as schedules all tasks.
Because of its central role, the kernel cannot be restarted without also stopping the computer.
Therefore, an updated version of the kernel cannot be used until the system is rebooted.
Shared Libraries
Shared libraries are units of code, such as
glibc
, which are used by a number of applications
and services. Applications utilizing a shared library typically load the shared code when the
application is initialized, so any applications using the updated library must be halted and
relaunched.
To determine which running applications link against a particular library, use the
lsof
command
as in the following example:
lsof /usr/lib/libwrap.so*
This command returns a list of all the running programs which use TCP wrappers for host access
control. Therefore, any program listed must be halted and relaunched if the
tcp_wrappers
package is updated.
SysV Services
SysV services are persistent server programs launched during the boot process. Examples of
SysV services include
sshd
,
vsftpd
, and
xinetd
.
Because these programs usually persist in memory as long as the machine is booted, each
updated SysV service must be halted and relaunched after the package is upgraded. This can be
done using the
Services Configuration Tool
or by logging into a root shell prompt and issuing
the
/sbin/service
command as in the following example:
/sbin/service <service-name> restart
In the previous example, replace
<service-name>
with the name of the service, such as
sshd
.
Refer to
Chapter 15, Network Configuration
for more information on the
Services Configuration
Tool
.