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Software

This section describes the Linux OS and GNU OE and compares them to the Solaris OE. Included are reference tables for commands and libraries.

This section contains the following topics:

"GNU Software"

"Distribution Methods"

"System Installation"

"Commands"

"Libraries"

"Documentation"

GNU Software

GNU (pronounced "guh-new") is the name of a project started in 1984 by Richard Stallman of MIT to develop open-source software and an operating system to run it on. The name itself is a programmer's joke and recursively stands for GNU's Not Unix. Most GNU software can be compiled and installed on a variety of operating systems, including virtually all versions of UNIX. The GNU software actually covers a large part of what we call Linux today. Linux itself really only refers to the kernel, whereas GNU refers to most of the software that runs in the environment that the kernel provides. Virtually all of the GNU software can be built and installed in Solaris as well. Since the release of Solaris 8, Sun packages GNU software on the Software Companion CD. In addition, Sun is migrating its windowing environment from OpenWindows and CDE to GNOME, the GNU Network Object Model Environment. For more information on GNU, refer to the GNU Web site at: http://www.gnu.org.

Distribution Methods

As mentioned in the previous section, most of the software that runs in Linux environment comes from the GNU project and is open source. Open source means that the software is distributed in the form of source code and that the source code is freely available to everyone. However, for the software to be useful, it must be compiled into machine code. It would be very cumbersome to go about compiling all of the software required to build a Linux system. From the ls command to the C compiler itself (gcc), all the software must be built from the source code. This fact is why there are numerous Linux distributions. A Linux distribution is released in the form of binaries that are easily installed onto a computer.

For Redhat, Mandrake, and Sun Linux, the distribution method is rpm package files. Initially, rpm stood for Redhat Package Manager, but now uses the same pun as the GNU acronym and stands for RPM Package Manager. The rpm package format is similar in functionality to a Solaris package and uses the rpm command to install or remove a package. Like pkgadd and pkgrm in Solaris, the rpm command is capable of checking dependencies; running pre-install, post- install, and remove routines; and installing into an alternate root directory. Extensive information about the functionality of rpm is available on the rpm(8) manual page. Further information is at http://www.rpm.org.

System Installation

The system installation process for most Linux distributions has come a long way since the original kernel was written. My own personal experience of installing Linux for the first time was with Slackware Linux in 1994. It required that I download and create 50 floppy diskettes. Each one of the diskettes contained a single package. In addition, the kernel needed to be compiled from source, because the stock kernel that was included to bootstrap the system only contained basic hardware support. On a machine with an Intel 486DX-33 processor, this compilation process sometimes took several hours.

Today, the installation process for most distributions is very simple and GUI driven. The basic steps for installing Linux are similar to those for installing the Solaris OE: identify the system, select the disk to install to, and choose which locales and software packages to install. Setting the configuration for your keyboard, video card, and mouse for X Windows is required, but these tasks are fairly simple because the installation program is usually capable of probing the hardware to figure out what drivers it needs. All that is usually required from a user is to decide what resolution and color depth to run at. The installation program prompts for how to install the boot loader, LInux LOader (LILO), or GRand Unified Bootloader (GRUB).

Commands

In Solaris OE, /bin is symbolically linked to /usr/bin. In Linux, these directories are separate and a distinction is made between the system binaries that go in /bin and application binaries that go in /usr/bin. In Solaris OE, application binaries typically get installed in /opt or /usr/local. Both operating environments have administrative commands in /sbin and /usr/sbin.

Most of the standard UNIX commands in Linux share a commonality with Berkeley Standard Distribution (BSD) rather than AT&T System V Release 4 (SVR4). The command-line arguments are taken mostly from BSD. Other commands are completely unique to Linux, but have similar counterparts in Solaris. TABLE 1 lists some commonly used commands in Solaris, with their counterparts in Linux. This list is not comprehensive. For a comprehensive list, consult Bruce Hamilton's UNIX Rosetta Stone Web site at http://bhami.com/rosetta.html.

TABLE 1 Common Solaris Commands Mapped to Linux Commands

Solaris Command

Linux Command

Purpose

df -k

df

List file systems in allocation units of KBytes

nawk

awk/gawk

Pattern scanning and processing language

ps -ef

ps -aux

List process status for all processes running

pkgadd

rpm -i

Add a software package

pkgrm

rpm -e

Remove a software package

gzcat file | tar -xvf -

tar -xzvf file

Unbundle a compressed tar file

cc

gcc

C compiler

xterm/dtterm

konsole/gnome-terminal

GUI terminal program

lpsched

lpd

Printer daemon

tip

minicom

Serial port access program

snoop

tcpdump

Network packet sniffer

patchadd

rpm -U

Install a software patch/update

priocntl -e

nice

Start a process with a given priority

priocntl -s

renice

Change the priority of a running process

prstat

top

Actively report process statistics

useradd

adduser

Add a user account

/sbin/swapadd

/sbin/swapon

Enable swap devices

format

fdisk

Manipulate disk partition tables

find / -print | grep xxx

locate xxx

Find a file

mount -F type

mount -t type

Mount a file system of type <type>

inetd

xinetd

Internet daemon

installboot

lilo

Install boot program

swap -l

/sbin/swapon -s

Display swap information

who -r

runlevel

Show run level

truss

strace

Trace a process


Libraries

As with binaries, there is a distinction between system libraries and application libraries in Linux. The system libraries are contained in /lib and the application libraries are contained in /usr/lib. Solaris does not make this distinction, because /lib is just a symbolic link to /usr/lib.

Both Solaris and Linux have a runtime linker responsible for linking executables to their shared library dependencies. The mechanism works very much the same way in both operating environments, as shown in TABLE 2.

TABLE 2 Linking Executables to Shared Libraries

Solaris

Linux

Function

/usr/lib/ld.so.1

/lib/ld-linux.so.1

Runtime linker

/var/ld/ld.config (32-bit)

/var/ld/64/ld.config (64-bit)

/etc/ld.so.conf

Linker configuration file

crle

ldconfig

Configure runtime linker

ldd

ldd

Show library dependencies


Documentation

In Solaris, virtually all software is documented in manual pages. The same is not true of Linux. While most of the basic UNIX commands, system calls, libraries, and system configuration files are documented in manual pages, other commands and software are documented in HOWTO and README files, GUI-based help programs, and on the Internet. Additionally, many rpm packages install the source code documentation under /usr/doc and /usr/share/doc. These locations are a good place to find pointers to additional documentation on the Internet, because these locations usually contain references to web pages of the software components.

A repository of documentation called the Linux Documentation Project is available on the Internet. This documentation contains numerous resources as well as most documentation from the sources mentioned previously. The Linux Documentation Project is located at http://www.tldp.org.

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