S

Samba

The Linux and Unix implementation of the Server Message Block protocol and the Common Internet File System (CIFS). Allows computers that run Linux and Unix to communicate with computers that run Microsoft Windows operating systems. I expect Samba 4.0, when released, to provide nearly full functionality as a Microsoft Active Directory Domain Controller.

secure virtual hosts

You can configure multiple secure virtual hosts on a single Apache server using the secure configuration file, /etc/httpd/conf.d/ssl.conf.

Security Enhanced Linux (SELinux)

An implementation of mandatory access control integrated into the Linux kernel; in essence, a different way of layering security within Linux.

sendmail

A standard e-mail server application used by most Internet e-mail.

Serial ATA (SATA)

The new standard on hard drives that makes it easier to chain hard drives in a series inside a physical system. SATA drives have device file labels similar to SCSI; for example, the first SATA drive is known as /dev/sda.

server

A computer that controls centralized resources such as files and printers. Servers can share these resources with client computers on a network.

setfacl

The setfacl command lets you control Access Control Lists (ACLs) on files and directories.

SGID

The SGID bit sets common group ID permissions on a file or directory.

Shadow Password Suite

The Shadow Password Suite creates an additional layer of protection for Linux users and groups in the /etc/shadow and /etc/gshadow files.

showmount

The showmount command lists the shared directories from an NFS server.

single-user mode

When you start RHEL in single-user mode, you're automatically logged in as the root user, without networking or most services. If your Linux system has boot problems, single-user mode may allow enough access to fix the problem.

smbpasswd

The smbpasswd command helps you create usernames and passwords for a Samba (Microsoft Windows) network.

SMTP (Simple Mail Transfer Protocol)

SMTP is a TCP/IP protocol for sending mail; used by sendmail.

SOA (Start of Authority)

In a DNS database, the SOA record is the preamble to all zone files. It describes the zone, the DNS server computer (such as ns.your-domain.com), the responsible administrator (such as [e-mail]), the serial number associated with this file, and other information related to caching and secondary DNS servers.

soft limit

Associated with user quotas. Specifies the maximum amount of space a user can have on a partition. Soft limits can be configured with grace periods.

spec file

Spec files are associated with source RPMs (SRPMS). You can modify an SRPM spec file to change the way an RPM package is built.

Squid

Squid is a high-performance HTTP and FTP caching proxy server.

SRPM (source RPM)

SRPMs include the source code required to build a binary RPM package. SRPMs are installed with the rpm -i command, which installs SRPM files within the /usr/src/redhat directory. You can then use the rpmbuild command to create a binary RPM.

Structured Query Language (SQL)

The basis for several database systems that can be run on Linux, including MySQL and PostgreSQL.

SUID

The SUID bit sets common user ID permissions on a file or directory.

superuser

The superuser represents a regular user who has taken root user privileges. Closely associated with the su and sudo commands.

swap space

Linux uses swap space for less frequently used data that would otherwise be stored in RAM. It is normally configured in Linux in a swap partition.

system-config-*

Red Hat has created a series of GUI configuration tools to help configure a number of different systems and services. You can start them with a number of different commands that start with system-config-*. While it's usually faster to configure a configuration file directly, not every experienced administrator knows every detail of every major configuration file.