Unix/Linux Introduction

Any Computer system consists of

     * Hardware
     * Operating System
     * Applications and Utilities

Unix is an operating system which was first developed in the 1960s in Bell Labs. Unix is a popular OS because of
multi user, multi tasking, stability and portability capabilities.

what is an Operating System?

   Operating system is a resource manager, which manages resources like CPU, Memory, Disks, printers, modems, network cards etc etc. Operating system acts as a host for the application programs which runs on the machine.
Unix/Linux Architecture:

      (1) kernel:

            Kernel is key part of Operating system which manages the kernel subsystems like process management, memory management, network management, filesystem, devices etc. This is heart of operating system which manages system and processes. Kernel provides an execution environment where applications runs.

       (2) Shell:

           The most generic term of shell means program where users run commands. Its a command interpreter. It takes input from the user and interacts with the kernel. It acts as an interface between kernel and user.

As far as i know, These are the following important shells.

               (a) Bourne Shell(sh)                                      

               (b) C shell(csh)

               (c) korne shell(ksh)
                
               (d) Bourne-again shell (bash)

               (f) z shell (zsh)

      To find out on what shell you are working depends on which shell the system administrator has specified as your default shell when your system was first installed.   All shells have their own initialization files.

To determine your login shell:

$ echo $SHELL

find the following to determine your default shell.

/bin/sh – Bourne shell

/bin/bash – Bourne Again shell

/bin/csh – C shell

/bin/ksh – Korn shell

/bin/zsh – Z shell

When you first login into the system, it runs the system profile file /etc/profile. after your system executes the system profile, then user profile will be run..User profile is the file where your environment is defined.

Depending on your default shell, user profile will be the following

.profile (Bourne and Korn shells)

.bash_profile (Bourne Again shell)

.login and .cshrc ( C shell)

User profile resides in each users home directory.

To find out your environment

Just type env command at your shell

$env

—————————————————

_=/usr/bin/env
SSH_TTY=/dev/pts/0
PATH=/oradata/app/oracle/product/10.2.0/bin:/usr/bin:/opt/ansic/bin:

/usr/ccs/bin:/usr/contrib/bin:/usr/contrib/Q4/bin:/opt/hparray/bin:

/opt/nettladm/bin:/opt

/fcms/bin:/usr/contrib/kwdb/bin:/usr/bin/X11:/opt/graphics/common/bin:

/opt/upgrade/bin:/opt/ipf/bin:/opt/resmon/bin:/opt/wbem/bin:

/opt/wbem/sbin:/opt/sas/bin

:/opt/sec_mgmt/bastille/bin:/opt/dsau/bin:/opt/dsau/sbin:/opt/firefox:

/opt/gnome/bin:/opt/ignite/bin:/opt/mozilla:/opt/perl/bin:

/opt/sec_mgmt/spc/bin:/opt/ssh/bin:/opt/hpsmh/bin:/opt/thunderbird:

/opt/gwlm/bin:/opt/sfm/bin:/usr/contrib/bin/X11:/opt/aCC/bin:

/opt/caliper/bin:/opt/cadvise/bin:/opt/langtools/bin:.

COLUMNS=179
EDITOR=vi
LOGNAME=oracle
MAIL=/var/mail/oracle
SFTP_UMASK=
SFTP_LOG_FACILITY=2
ORACLE_SID=PROD
ERASE=^H
SFTP_PERMIT_CHOWN=1
USER=oracle
SHELL=/sbin/sh
LOG_SFTP=0
SFTP_LOG_LEVEL=3
HOME=/home/oracle
TERM=xterm
ORACLE_HOME=/oradata/app/oracle/product/10.2.0
TZ=WAT-3
SFTP_PERMIT_CHMOD=1
LINES=40
$
———————————————————

above output is from my HP-UX Oracle user Environment

These are the main distributions of Unix, which are more popular:

                  (a) AIX ( IBM)   (Aix 6.1 is the latest version)
                  (b) HP-UX ( HP)  (11i V3 is the latest version)
                  (c) Solaris (Sun Microsystems) (Solaris 10 is the latest version)

we have following Linux Distributions, which are more popular

                 (a) RedHat Enterprise Linux (RHEL 5 is the latest version)
                 (b) SuSe Enterprise Linux   (SuSe 10 is the Latest Version)
                 (c) Oracle Enterprise Linux (Oracle Enterprise Linux 5 is the Latest Version)

For supported Unix/Linux versions for Oracle Applications 11i and Release 12, check the following link.
http://www.oracle.com/technology/support/metalink/index.html

Reference: 

           http://docs.sun.com/app/docs/prod/solaris.10
            http://docs.hp.com/en/oshpux11iv3.html

About the Author AppsDBA

Leave a Comment:

15 comments
lakshmikanthan says June 11, 2008

hi
this is very useful for me.
Thank you
lakshmi

Reply
SubbaRao says June 11, 2008

Always welcome my friend

Regards,
Subbu

Reply
Geetha M says June 16, 2008

Expecting more such informative articles.
For me it refreshed all my unix basic stuff.
Thankyou very much subbarao.

Rgds
Geetha M

Reply
SubbaRao says June 17, 2008

always welcome geetha.

Regards,
Subbu

Reply
lakshmikanthan says June 17, 2008

hi,

i am fresher in oracle application dba
this is a small questions but important

we are using several kind of tops
example
cd $APPL_TOP
cd $JAVA_TOP
cd $INV_TOP

so, cd means its one of directory this top or the directory’s where it has stored in server.

Thanks
lakshmi

Reply
SubbaRao says June 18, 2008

Lakshmi,

cd means –> change directory (in short form cd)

for suppose, if i want to go to directory admin in /u01/prodappl directory…path is like this

/u01/prodappl/admin

presently I am in /u01 directory..you can check this by typing pwd (present working directory)

#pwd
/u01

#ls ( List the files/directories in present u01 directory)

prodappl prodcomn prodora

so i want to go prodappl directory…

#cd prodappl ( this will change directory to prodappl)

then last go to admin dirctory..

#cd admin

Regarding all these basics,I will describe these basics in my next Unix article. it will be coming soon…

Hope it helps,

Good luck,

Regards,
Subbu

Reply
lakshmikanthan says July 15, 2008

hi
how to change the ownership of the link file

thanks
lakshmi

Reply
dpexpress says November 8, 2008

dear Rao

doing superb job

keeep it up

Reply
SubbaRao says November 9, 2008

Thank you friend…

Regards,
SubbaRao

Reply
ashwin says November 19, 2008

Really nice information for refreshing unix fundamentals and expecting much more stuff on the same.

Nice job, Keep it up.
Thanks,
Ashwin

Reply
dhanrajsnikam@yahoo.co.in says January 26, 2009

How do i increase speed of oracle apps database?

Its being very slow

Reply
firdous ahmad says May 4, 2009

Respected sir.

i Bsc. life science student.. i completed the oracle dba course, now i am confused what to do further . shall i go for apps dba and oracle busines intelligance, is their any relation between , what are the job scope for both..will it not be problem for me being bsc life student? waiting for ur reply sir..
with regards
firdous
9886403195

Reply
raju says March 9, 2010

Hi to determine the shell, echo $SHELL does not work always.

Reply
Ashish says August 22, 2013

Anyone help please :

We have some services running on Linux/Solaris server which picks up the email from Microsoft Exchange Mailbox. Sometimes the messages get piled up(stuck/not picked up by service) in the mailbox as services don’t pick them up. These are very important email messages. I have checked in the service logs but didn’t find any failure.

Please if someone advise if i can set any alert on linux server or mailbox which tells that the email messages are not picking up.

Reply
Ashish says February 21, 2014

Hi Team,

I have received a root CA certificate from third party that needs to be installed/add on my GNU/Linux machine.

I have checked some online answers for it and they suggest that to add the cert in dir /usr/share/ssl/certs/ca-certificates however i am not able to find this directory anywhere on my machine :

i have below directory available :

# pwd
/usr/share/ssl/certs

# ls -ltr
total 264
-rw-r–r– 1 root root 1832 Dec 7 2010 Makefile
-rw-r–r– 1 root root 610 Dec 7 2010 make-dummy-cert
-rw-r–r– 1 root root 249373 Dec 7 2010 ca-bundle.crt

Any help much appreciated

Reply
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