Introduction to Unix Operating System โดย อ.ณัฐกร เฉยศิริ

Agenda An Overview of the UNIX Unix Installation Pre Install Post Install Startup & Shutdown Shell & Unix Command File System Account Management Network File System (NFS) Install Additional Software Package Management Install Form Source Code Process & Job control

An Overview of the Unix OS At first, unix was designed to let a number of programmer access the same time and share its resource. The important features that make unix favorite are: Multitasking Multiuser Portability Unix Tools Unix Communication Library of application software

Unix Structure Application Program Kernel Hardware

Information before install Size of Memory and Hard Disk Bandwidth and Memory of Video Card Mouse type Host Name Network information such as IP address, Gateway,Network Address,DNS Server Time Zone Root Password

Choose Installation Class Core system support Contains the minimum software required to boot and run Solaris. but not include the OpenWindows software. End-user system support Contains the core system support software plus end user software, which include OpenWindows and the Common Desktop Environment software. Developer system support Contains the end-user software plus libraries, include files, man pages, and programming tools for developing software. Entire distribution. Contains the entire Solaris 8 release. Entire distribution plus OEM system support Contains the entire Solaris 8 release software plus extended hardware support.

Partition Your HDD Single VS Mulitple Allow finer control over such task as a backup If one file system corrupted the others remain intact Allow you control amount of storage for allocate type of use Easy for manage All the space on the disk is available for anyone to use

Partition Scheme Root (/) swap /usr /var /home

Post Install Setup Network Connection Install Additional Software Configure others service such as Printer ,NFS,WWW etc

Network Configuration Display and configure the network interface using the “ifconfig” command Ensure that the DNS is configured in file /etc/resolv.conf Ensure that the routing table is set by command “netstat –r” Ensure that the gateway is set in file /etc/defaultrouter

Start up Before the UNIX operating system can perform correctly, there are a number of steps that must be followed The failure of any one of these can mean that the system will not start. It is important for the Systems Administrator to be aware of what happens during system startup so that any problems that occur can be remedied.

Booting - consists of the following steps ROM Phase Boot Program Phase Kernel initialization Phase Init Phase

Boot ROM Phase After turn on power to the system, the ROM will display system identification and run self-test diagnostics to verify system hardware Then the ROM will loads primary boot program called bootstrap program that store in bootblock of a boot device

Boot Program Phase The boot strap program find and execute the secondary boot program from the file system and load it into memory After the secondary boot program is loaded, it will load the kernel

Kernel initialization Phase The kernel initializes itself (Create process control and other data structures) Load device driver modules Mounts the necessary file system Create the process 0 (swapper) Then, bring the system to “initdefault” state specified in /etc/inittab

Swapper The first task for the kernel is to start the swapper process. The swapper process is the part of the kernel that schedules all other process. The swapper has process ID of 0 It’s first job is to start up the init process

Init Phase The kernel start /sbin/init process, which starts other process by reading the /etc/inittab file The /sbin/init process start the run control scripts

Run Control Script Each init state has a corresponding series of run control scripts The init process executes the /sbin/rc<n> script which execute a series of other scripts located in /etc/rc<n>.d directory All run control scripts are also located in the /etc/init.d directory. These file are linked to run control scripts in /etc/rc<n>.d directory

Run Level Run level Description Halt the machine 1 Halt the machine 1 Single user mode. All file systems mounted, only small set of kernel processes running. only root can login. 2 multi-user mode , without remote file sharing 3 multi-user mode with remote file sharing, processes, and daemons 4 undefine 5 used for to start X11 on boot 6 shutdown and reboot s or S same as single-user mode

Shutdown A UNIX machine should (almost) never be just turned off. It is also important for the Systems Administrator to understand what the correct mechanism is to shut a UNIX machine down There are a number of steps to carry out to ensure that the operating system and many of its support functions remain in a consistent state.

Step before shutdown Commands to shut down List of all logged-in user by “who” command. You might sent broadcast message to let user know the system being shutdown Flush file system buffer to physical disk by “sync” Use Shut Down command Commands to shut down /usr/sbin/shutdown /sbin/init /usr/sbin/halt /usr/sbin/reboot

Unix Shell Unix is a layered operating system. The OS not allow applications accessing the hardware directly. The shell acts as a command interpreter. It takes each command and passes it to the operating system kernel to be acted upon. And then displays the results of this operation

Relationship for Kernel,Shell and Application

Features provided by the shell The shell provides you with one or more of the following features.

Types of shell There are several different shells available for Unix. The most popular are described here. Bourne shell (sh) C shell (csh) Korn shell (ksh) Bourne Again Shell (bash)

Unix Command A command is a program that tells the Unix system to do something. Usually has the form: command [options] [arguments] Commands are case sensitive. command and Command are not the same. Options and syntax for a command are listed in the man page

Navigation and Directory Control Commands

File Maintenance Commands

Miscellaneous commands

Unix file type Regular file. A common file which contains data in text or binary. Directory file. A file that contains name of other files and point to information on these files. Symbolic link. A type of file that point to another file.

Unix file type Character devices file. A type of file use for certain type of devices(read-write data in one character). Block devices file. A type of file use for certain type of devices(read-write data in block). FIFO. A type of file that use for interprocess communication,some time call named pipe. Socket. A type of file that use for network communication.

Regular File A regular file simply holds data. Perhaps the most common file type found in the Solaris Operating Environment are regular files, which allow you to store many different kinds of data. Regular files can hold ASCII text, binary data, image data, databases, application-related data, and more.

Directory file Directories store information that associates file names with inode numbers. Unlike regular files that can hold many different kinds of data, directories can hold only one kind.

Symbolic link A symbolic link is a file that points to another file. Like directories, symbolic links contain only one kind of data. A symbolic link contains the pathname of the file to which it points.

File type & symbol Type Symbol Regular file - Directory d Character device c Block device b Unix domain socket s Name pipes p link file l

File Access Permission Symbol Permission Means r Read Can open and read content of file w Write Can write to file(Modify content) or delete it x Execute Can execute the file(if it program or shell script) - Denied Cannot read, write or execute file

Group Type Owner Others - r w x - - x r - x d r w x r - x r - - Example 1 Example 2 d r w x r - x r - - 22 + 21 + 20

The following example shows the use of the ls –la command to display permission file

Permission and Owner Command chmod [–R] permission filename Changes access permission of a file. chown [-R] username:groupname filename Changes the ownership of a file. chgrp [-R] groupid filename Changes the group ownership of a file.

Account Management Every user on a UNIX machine must have an account. Components of a user account are: login name (also called a username). password. The numeric user identifier or UID. The numeric group identifier or GID. home directory. login shell. startup files.

Add use from GUI tools

Configuration files related to user accounts /etc/passwd the password file, holds most of an account characteristics including username, UID, GID,GCOS information, login shell, home directory /etc/shadow the shadow password file, a more secure mechanism for holding the password /etc/group the group file, holds characteristics about a system's groups including group name, GID and group members

Fields in /etc/passwd file Each line in the /etc/passwd file contains several fields, separated by a colon ( : ) , and is formatted as follows: username:password:uid:gid:comment: home-directory:loginshell

Fields in /etc/shadow file Each line in the /etc/shadow file contains several fields, separated by a colon ( : ) , and is formatted as follows: username:password:lastchange:min:max: warn:inactive:expire

Startup Files Once the home directory is created the startup files can be copied in or created. Again you should remember that this will be done as the root user and so root will own the files. You must remember to change the ownership. For example The following is example set of commands that will perform these tasks. mkdir home_directory cp -pr /etc/skel/.* home_directory chown -R login_name home_directory chgrp -R group_name home_directory chmod -R 700 home_directory

The NFS Distributed File System The NFS environment contains the following components: NFS server – A system that contains the file resources to be shared with other systems on the network. NFS client – A system that mounts the file resources shared over the network and presents the file resources as if they were local.

Configuring the NFS File Server To set up an NFS server, complete the following steps: Edit the /etc/dfs/dfstab file and add those file resources to be automatically shared whenever the system enters run level 3. For example: # share -F nfs /usr/share/man 2. Start the NFS server daemons by invoking the following: # /etc/init.d/nfs.server start This shares the contents of the /etc/dfs/dfstab file.

The NFS Client Setup 1. Use the /usr/sbin/dfshares command to display a server’s available resources. # dfshares host1 2. Use the /usr/sbin/mount command to access the remote file resource. # mount host1:/usr/share/man /usr/share/man 3. To unmount the remote file resources from the client by using the /usr/sbin/umount command. # umount /usr/share/man

Install Software Using Package Management pkginfo command to display information about the software packages that have been installed pkgadd command uncompresses and copies files from the installation media to the local system’s disk. pkgrm command deletes all files associated with that package unless those files are also shared with other packages.

Install Software From Source Code Tool & Utility for Compile Source code Compiler & Library (GNUgcc & libgcc) Make (GNUmake) Autoconfigure (GNUautoconfigure) Compress/Uncompress (gzip/gunzip/tar)

Apache Web Server Install Overview for install apache $ ./configure --prefix=PREFIX $ make $ make install NOTE: PREFIX by default use "/usr/local/apache"

Configuration File Finally you can customize your Apache HTTP server by editing the configuration files $ vi PREFIX/conf/httpd.conf $ vi PREFIX/conf/access.conf $ vi PREFIX/conf/srm.conf And Statrt web server by $PREFIX/bin/apachectl start

Most Important Configure ServerName avalon.bu.ac.th ServerAdmin root@avalon.bu.ac.th DocumentRoot "/usr/local/apache/htdocs" *Note ServerRoot and DocumentRoot is difference meaning

Process & Job control A Unix process is an instance of an executing program It has a separate existence from all the other processes on the system we say that each process has its own address space A unique number known as its process-id or pid The pid of its parent process is the process which started it, usually a shell

Process state Processes also have state One a single-CPU machine, only one process is running Most processes are sleeping, waiting for input or output to finish There are a few other odd states: swapped, zombie, or stopped.

Job control The mechanism that shuffle processes from foreground, background and stopped is known as job control Job control requires three condition for support A shell that support job control. The terminal driver in the kernel must support job control Support for certain job-control signals must be provided.

Foreground and Background Tasks Unix allows running processes to be disconnected from their terminals Unix has the concept of foreground processes which are attached to a user's terminal background processes, which have no terminal to read from

Job control & process management command ps - report process status kill - terminate or signal processes Control process execution jobs - report job status bg - bring job to background process fg - bring job to foreground process stop - stop the job

Signals Signals are a technique used to notify a process that some condition has occurred. Ordinary users can only send signals to their own processes. The command to send signal to process is “kill”. example: $ kill -signal processid

Here are some examples: $ sleep 100 # Wait for 100 seconds, then go back to shell ctrl-C # Kill sleep process $ sleep 100 & # Wait for 100 seconds in the background $ jobs # Show list of jobs [1] + Running sleep 100 & $ kill SIGSTOP %1 # Stop sleep process (job number 1) $ jobs [1] + Stopped (SIGSTOP) sleep 100 & $ bg %1 # Put sleep in background $ fg %1 # Bring sleep in foreground, reattached # to the terminal