1) What are the main differences between RHEL4 & RHEL5? Answer

difference between RHEL 4 and RHEL 51)In RHEL 4 SELinux Block only 13 services, But on RHEL 5SElinux Block 80 services2) RHEL 4 have ext2 filesystem, but RHEL 5 we have ext3filesystem That support Journal3)RHEL 4 have no virtualization Feature, but in RHEL 5 wehave virtualization with Hypervisor-V 4)In RHEL 4 we have no Yum, But in RHEL 5 we have Yum available

any many more....... need more time to describe it

(or)

rhel4 rhel5no yum server yum serverselinux Advanced selinuxsecure more secureno cdkey cd key--- virtualizationmim 256 mb ram 512 ram--- better support for Red Hat Directory

Ext4 (on latest version)2. What is the difference between Telnet and SSH?

Answer: SSH using PORT 22 and telnet using Port 23ssh is a secured shell, where telnet is not a securedone.when you ssh to trasnfer data between a system, the datawill be send in the encrypted form, where the hacker cannotencode or decode it. While you telnet,the data send betweenthe system is alphabetical format(ASCII), where every onecan understand. More over as per network security, telnetand ftp are prohibited. Always, trust SSL based data transfer.

How to recover a deleted file in linux ? AnswerDetermine the partition in which the file you wish torecover was located by using the command pwd (present workdirectory)and unmount the current directory by using the commandumount. Use the "debugfs" command. The "debugfs" command is

used to handle most major errors and bugs that can occur inLinux by using #debugfs /usr/directory name.Use the "lsdel"once you have begun the debug of the file system.Recoverthose files you wish to undelete and take backup of that file

What is the difference between home directory and working directory? Answerhome directory is one over which user have complete controland it is its default working directory when its logs in.while the working directory is the users current directorywhich may or may not be his home directory.

What is the minimum number of partitions you need to install Linux? AnswerWell in my opinion is case if minimum nukber of partition isasked then better answer would be //boot/swapYou can install linux with minimum of three partitions. Tell me the 5 differences between Linux and Unix? AnswerUnix and Linux1. UNIX is very old and Linux is based on it2. Linux is a good desktop OS while UNIX lacks the userfriendliness needed for general computing3. UNIX is intended for mainframes and high end computersand cannot run on mos PCs while Linux can go from mainframesdown to low end personal computers4. UNIX is proprietary while Linux is shared using theLicensing of the GNU5.Linux file system is ext36.Selinux enabled on linux7. linux using advanced file editor like vim

How do i check which nfs version I am using ???????? Answerrpm -qa | grep nfsHow to check all open ports on linux machine and block unsed ports???????? Answer# 3 #netstat -tulpor#netstat -tulpn

to verfy the open ports

How can you see all mounted drives? Answer# 8 mount -lis the perfect answer, as this commands lists all themounted drive / partitions in the system ( temperory orpermenent), here root / user may have mounted / unmountedsome other partitions

fstab gives us the information that which partitions has tobe mounted whenever the system starts.  what restrict telnet for root itself but allow for other user Answer# 1 vi /etc/pam.d/login

auth required pam_securetty.so== 1st line should be placed as required.if we change the option as sufficient instead of required telnet can login as "root". tell me some of the Linux HotKeys do you know? Answer# 1 alt+f1 for application menuctl+l to clear screenalt+f2 to open run application windowalt+f3 for find alt+f4 to close applicationalt+f9 to minimise window

How to trace any process background processing? Answer# 1 ps -auxwhat is difference between $@ and $* in UNIX Shell script Answer# 1 In a shell script :

$@: each quoated string treated as a separate argument while gving at command line.

$*: stores the complete set of positional parameters as a single stri