Is CentOS 6 a good tool to pass RHCSA and RHCE exams certification?

jomavilla24 · 02-11-2012, 09:56 AM

Hi everyone:

I recently have initiated my life in the linux world and I´d like to obtain the first certification of red hat (RHCSA) and maybe, in the future, obtain the RHCE. Since both exams are based in RHEL 6 I need something to practice, but in order to have RHEL6 you must pay. So I heard that CentOS is very similar to RHEL, but what version of CentOS do you recommend to practice and pass both exams?

Thanks so muchs guys!

Martin

yooy · 02-11-2012, 10:12 AM

always practice the newest version. Take a look also at Fedora, free version of Red Hat.

mike_rhce · 02-11-2012, 11:01 AM

While CentOS 6 and Scientific Linux 6 are excellent options, I tell people who are interested in Red Hat certs to avoid Fedora.

Yes, Fedora is a testbed for Red Hat developers. But the latest versions of Fedora include features not found in RHEL 6. In fact, RHEL 6 is based on something in between Fedora 12 and 13. While I suppose you could mix both, it's easier to just use CentOS 6 or Scientific Linux 6.

stef80 · 02-11-2012, 02:18 PM

Quote:

Originally Posted by yooy

always practice the newest version. Take a look also at Fedora, free version of Red Hat.

Any minor version within version 6 will do, why presume you'll get latest on the exam?

Definitely not Fedora, for the reasons mike already explained. CentOS 6, Scientific Linux 6, RHEL 6 server - any of them will do. BTW, RHEL 6 server can be obtained for free. One just needs to register at Red Hat for a 30-day trial license (which only covers 30-day access to RHN, updates).

mike_rhce · 02-11-2012, 06:08 PM

Dear Stef,

You're right on all counts. One thing to watch out for -- users who get RHEL 6 with the 30-day trial license --

If I understand correctly (I have an actual subscription myself, so I'm not 100% sure)

they won't be able to get updates from the Red Hat Network once those 30 days are up -- nor will they be able to use commands like yum to install additional packages over the network.

However, I do detail the procedure for creating a repository from the installation DVD in Chapter 7, based on a default FTP server created in Chapter 1.

stef80 · 02-13-2012, 05:53 AM

Quote:

Originally Posted by mike_rhce

However, I do detail the procedure for creating a repository from the installation DVD in Chapter 7, based on a default FTP server created in Chapter 1.

Agree. For exam preparation purposes, local repo is best option (so, you don't actually need RHN access / updates).

red.hive · 10-11-2012, 02:39 PM

Hi,

I posted this today, addressed to mike.rhce in a different thread, but now that I see this thread here, it seems more appropriate - also perhaps others might be able to help as well.

Anyways, I bought Michael Jang's book (6th edition) and couple of days ago I received it on the mail! I have to say it looks great :-)

I am thinking about the best setup option for my studies, so I have a few questions for you, I would really appreciate if you could help:

1) Even though people say that CentOS and Scientific Linux are good enough to learn for the RHCSA/RHCE, I was told that it is not ideal - not only because of the look and feel that are different, but also because they are not as similar to RHEL as people might think - and that on exam time it might be confusing. Do you agree with that?

2) Assuming that the best option for the exam is really RHEL, then comes the question of price: I received in my course the 30 day trial disk, with the RPMs - and I built the local repo from the CD...but...there are so many packages missing from there (for instance, no tigervnc available and so on)...that doesn't seem like a good option either....so...I am coming to the conclusion that I will have to order a RHEL license...what do you think? Any way to get a decent repo for the trial version?

3) Now, assuming that I will use RHEL (be it trial version or license), comes the question of hardware. I only have one computer that I can use, and I have vmware workstation installed. I imagine there is no problem installing RHEL on vmware workstation and doing all the studies from there - my only question would be regarding the KVM part - would I be able to use KVM inside a redhat VMware? Or would I need to install redhat on the host (more problematic for me) in order to be able to use KVM?

4) Does KVM even work on the trial version?

Thanks in advance for your help and for the great book!

PS: administrators, if posting the same twice is a problem, pls delete one of my posts, thanks!

red.hive

custangro · 10-11-2012, 03:15 PM

Quote:

Originally Posted by red.hive

Hi,

I posted this today, addressed to mike.rhce in a different thread, but now that I see this thread here, it seems more appropriate - also perhaps others might be able to help as well.

Anyways, I bought Michael Jang's book (6th edition) and couple of days ago I received it on the mail! I have to say it looks great :-)

I am thinking about the best setup option for my studies, so I have a few questions for you, I would really appreciate if you could help:

1) Even though people say that CentOS and Scientific Linux are good enough to learn for the RHCSA/RHCE, I was told that it is not ideal - not only because of the look and feel that are different, but also because they are not as similar to RHEL as people might think - and that on exam time it might be confusing. Do you agree with that?

2) Assuming that the best option for the exam is really RHEL, then comes the question of price: I received in my course the 30 day trial disk, with the RPMs - and I built the local repo from the CD...but...there are so many packages missing from there (for instance, no tigervnc available and so on)...that doesn't seem like a good option either....so...I am coming to the conclusion that I will have to order a RHEL license...what do you think? Any way to get a decent repo for the trial version?

3) Now, assuming that I will use RHEL (be it trial version or license), comes the question of hardware. I only have one computer that I can use, and I have vmware workstation installed. I imagine there is no problem installing RHEL on vmware workstation and doing all the studies from there - my only question would be regarding the KVM part - would I be able to use KVM inside a redhat VMware? Or would I need to install redhat on the host (more problematic for me) in order to be able to use KVM?

4) Does KVM even work on the trial version?

Thanks in advance for your help and for the great book!

PS: administrators, if posting the same twice is a problem, pls delete one of my posts, thanks!

red.hive

I know Mr Jang will answer you...but I can explain my experience.

1) True, the RHEL "clones" are not 100% binary compatible. And it's best to have the "real deal" when studying. HOWEVER - (this is my personal experience); I've used CentOS for my RHCE5 test and passed. In fact...the first time I've ever used a RHEL system was during the RHCE5 test. So it's more than capable to suit your study needs.

2) For my RHCE 6 test, I used the Trial version of RHEL 6 (the 30 day one) with no problem. Setting up the CD repo is fine for after the 30-day period. (That's what I did)

3) I STRONGLY suggest (as does Mr Jang in his book) that you use KVM on a machine. I installed RHEL 6 on a dual-boot system on my desktop so I can use KVM you can do the same. It's highly recommended that you install RHEL on a "bare metal" system, then use KVM. You cannot use KVM inside of RHEL that's running on VMWare

4) KVM comes on the 64bit version of the OS

HTH

--C

red.hive · 10-13-2012, 12:51 PM

Thank you very much custangro, very useful answers!

May I ask how many years of experience you had with linux before you took the test? I have been using linux for a few years now, but only as a user, not sys admin. I hope I manage to study enough to pass!

Do you think that the CentOS look and feel (being different than the original rhel) might confuse a "newbie" like me at exam time?

Also - why did you decide to go for a dual boot? Any special study related reason?

And regarding KVM - does CentOS have it as well?

Again, many thanks for your help and insights!

red.hive

custangro · 10-15-2012, 11:43 AM

Quote:

Originally Posted by red.hive

Thank you very much custangro, very useful answers!

May I ask how many years of experience you had with linux before you took the test? I have been using linux for a few years now, but only as a user, not sys admin. I hope I manage to study enough to pass!

Do you think that the CentOS look and feel (being different than the original rhel) might confuse a "newbie" like me at exam time?

Also - why did you decide to go for a dual boot? Any special study related reason?

And regarding KVM - does CentOS have it as well?

Again, many thanks for your help and insights!

red.hive

1) I only had about 1 1/2 years with Linux before I took my RHCEv5 test. But I was 100% exclusively using a Red Hat variant. I studied Jang's book until I knew it inside and out. My suggestion, go through each chapter and don't move on to the next one until you KNOW it.

2) It won't confuse you. The difference between RHEL and CentOS is logos. CentOS is as close to "binary compatible" as it gets

3) I went for a dual boot because I didn't have a "spare" computer to study. My suggestion? If you have a spare computer, install RHEL/CentOS on it (without dual boot).

4) CentOS has KVM...but only the 64bit version

HTH

-C

red.hive · 10-16-2012, 07:51 AM

Hi custangro,

Thank you for sharing your experience - I have to say I got very encouraged by your post and I will most definitely be following your advice.

Jang's book seems very thourough and it is *huge* - I am thinking it will take me about 6 months (at least) to manage to get an in depth look into all these almost 1000 pages :-)

Thanks again,

red.hive

red.hive · 10-16-2012, 02:53 PM

Hello again,

I started installing RHEL, decided to use the trial version for now, and encountered a few problems, one I will ask here and the other, a networking issue, I will ask at the networking section.

What I want to ask here is regarding a sort of dual boot issue: @custangro, you advised not to use dual boot - but - I went for it because I remembered that I actually have two separate hard drives, which in the end is like installing in bare metal. In one, with 1 TB, I have an Ubuntu system installed. The other, with 160 GB, I used only for storage and almost forgot it was there. So I decided to use it for the RHEL installation. The problem I have is that when I boot the computer, Ubuntu's grub doesn't "see" the RHEL installation on the other hard drive and vice versa, RHEL's grub does not see the Ubuntu installation. So each time I boot, I need to go to the BIOS first and choose with which drive to boot. Is there any way to make each respective GRUB recognize the other system and offer it as an option to boot? Or because it is in a different hard drive it wont work?

Many thanks in advance for any help, it is quite annoying having to change the boot order every time :-)

red.hive

custangro · 10-16-2012, 03:06 PM

Can you post the menu.lst and/or the grub.conf file of the RHEL system and the Ubuntu system

--C

red.hive · 10-16-2012, 03:34 PM

This is the grub from Ubuntu. I will post the one from RHEL as soon as I get there again - I dont have internet in there as RHEL is not recognizing my network card, so I can only post in the forum while inside my Ubuntu :-). The only entry that appears in RHEL grub menu is RHEL6 (only one line, nothing more). I am posting the Ubuntu grub for now (and super thanks!)

cat /boot/grub/grub.cfg;

Code:

#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#

### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
  set have_grubenv=true
  load_env
fi
set default="0"
if [ "${prev_saved_entry}" ]; then
  set saved_entry="${prev_saved_entry}"
  save_env saved_entry
  set prev_saved_entry=
  save_env prev_saved_entry
  set boot_once=true
fi

function savedefault {
  if [ -z "${boot_once}" ]; then
    saved_entry="${chosen}"
    save_env saved_entry
  fi
}

function recordfail {
  set recordfail=1
  if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi
}

function load_video {
  insmod vbe
  insmod vga
  insmod video_bochs
  insmod video_cirrus
}

insmod part_msdos
insmod ext2
set root='(hd0,msdos1)'
search --no-floppy --fs-uuid --set=root 
if loadfont /usr/share/grub/unicode.pf2 ; then
  set gfxmode=auto
  load_video
  insmod gfxterm
  insmod part_msdos
  insmod ext2
  set root='(hd0,msdos1)'
  search --no-floppy --fs-uuid --set=root 
  set locale_dir=($root)/boot/grub/locale
  set lang=en_US
  insmod gettext
fi
terminal_output gfxterm
if [ "${recordfail}" = 1 ]; then
  set timeout=-1
else
  set timeout=10
fi
### END /etc/grub.d/00_header ###

### BEGIN /etc/grub.d/05_debian_theme ###
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
if background_color 44,0,30; then
  clear
fi
### END /etc/grub.d/05_debian_theme ###

### BEGIN /etc/grub.d/10_linux ###
function gfxmode {
	set gfxpayload="${1}"
	if [ "${1}" = "keep" ]; then
		set vt_handoff=vt.handoff=7
	else
		set vt_handoff=
	fi
}
if [ "${recordfail}" != 1 ]; then
  if [ -e ${prefix}/gfxblacklist.txt ]; then
    if hwmatch ${prefix}/gfxblacklist.txt 3; then
      if [ ${match} = 0 ]; then
        set linux_gfx_mode=keep
      else
        set linux_gfx_mode=text
      fi
    else
      set linux_gfx_mode=text
    fi
  else
    set linux_gfx_mode=keep
  fi
else
  set linux_gfx_mode=text
fi
export linux_gfx_mode
if [ "${linux_gfx_mode}" != "text" ]; then load_video; fi
menuentry 'Ubuntu, with Linux 3.2.0-32-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	linux	/boot/vmlinuz-3.2.0-32-generic root=UUID= ro   quiet splash $vt_handoff
	initrd	/boot/initrd.img-3.2.0-32-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-32-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root
	echo	'Loading Linux 3.2.0-32-generic ...'
	linux	/boot/vmlinuz-3.2.0-32-generic root=UUID= ro recovery nomodeset 
	echo	'Loading initial ramdisk ...'
	initrd	/boot/initrd.img-3.2.0-32-generic
}
submenu "Previous Linux versions" {
menuentry 'Ubuntu, with Linux 3.2.0-31-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root
	linux	/boot/vmlinuz-3.2.0-31-generic root=UUID= ro   quiet splash $vt_handoff
	initrd	/boot/initrd.img-3.2.0-31-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-31-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root
	echo	'Loading Linux 3.2.0-31-generic ...'
	linux	/boot/vmlinuz-3.2.0-31-generic root=UUID= ro recovery nomodeset 
	echo	'Loading initial ramdisk ...'
	initrd	/boot/initrd.img-3.2.0-31-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-30-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	linux	/boot/vmlinuz-3.2.0-30-generic root=UUID= ro   quiet splash $vt_handoff
	initrd	/boot/initrd.img-3.2.0-30-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-30-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	echo	'Loading Linux 3.2.0-30-generic ...'
	linux	/boot/vmlinuz-3.2.0-30-generic root=UUID= ro recovery nomodeset 
	echo	'Loading initial ramdisk ...'
	initrd	/boot/initrd.img-3.2.0-30-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-29-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	linux	/boot/vmlinuz-3.2.0-29-generic root=UUID= ro   quiet splash $vt_handoff
	initrd	/boot/initrd.img-3.2.0-29-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-29-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	echo	'Loading Linux 3.2.0-29-generic ...'
	linux	/boot/vmlinuz-3.2.0-29-generic root=UUID=ro recovery nomodeset 
	echo	'Loading initial ramdisk ...'
	initrd	/boot/initrd.img-3.2.0-29-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-27-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	linux	/boot/vmlinuz-3.2.0-27-generic root=UUID= ro   quiet splash $vt_handoff
	initrd	/boot/initrd.img-3.2.0-27-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-27-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	echo	'Loading Linux 3.2.0-27-generic ...'
	linux	/boot/vmlinuz-3.2.0-27-generic root=UUID= ro recovery nomodeset 
	echo	'Loading initial ramdisk ...'
	initrd	/boot/initrd.img-3.2.0-27-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-26-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	linux	/boot/vmlinuz-3.2.0-26-generic root=UUID=ro   quiet splash $vt_handoff
	initrd	/boot/initrd.img-3.2.0-26-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-26-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	echo	'Loading Linux 3.2.0-26-generic ...'
	linux	/boot/vmlinuz-3.2.0-26-generic root=UUID= ro recovery nomodeset 
	echo	'Loading initial ramdisk ...'
	initrd	/boot/initrd.img-3.2.0-26-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-25-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	linux	/boot/vmlinuz-3.2.0-25-generic root=UUID= ro   quiet splash $vt_handoff
	initrd	/boot/initrd.img-3.2.0-25-generic
}
menuentry 'Ubuntu, with Linux 3.2.0-25-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	echo	'Loading Linux 3.2.0-25-generic ...'
	linux	/boot/vmlinuz-3.2.0-25-generic root=UUID=ro recovery nomodeset 
	echo	'Loading initial ramdisk ...'
	initrd	/boot/initrd.img-3.2.0-25-generic
}
menuentry 'Ubuntu, with Linux 3.0.0-21-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	linux	/boot/vmlinuz-3.0.0-21-generic root=UUID= ro   quiet splash $vt_handoff
	initrd	/boot/initrd.img-3.0.0-21-generic
}
menuentry 'Ubuntu, with Linux 3.0.0-21-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root
	echo	'Loading Linux 3.0.0-21-generic ...'
	linux	/boot/vmlinuz-3.0.0-21-generic root=UUID=ro recovery nomodeset 
	echo	'Loading initial ramdisk ...'
	initrd	/boot/initrd.img-3.0.0-21-generic
}
}
### END /etc/grub.d/10_linux ###

### BEGIN /etc/grub.d/20_linux_xen ###
### END /etc/grub.d/20_linux_xen ###

### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry "Memory test (memtest86+)" {
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	linux16	/boot/memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 
	linux16	/boot/memtest86+.bin console=ttyS0,115200n8
}
### END /etc/grub.d/20_memtest86+ ###

### BEGIN /etc/grub.d/30_os-prober ###
### END /etc/grub.d/30_os-prober ###

### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###

### BEGIN /etc/grub.d/41_custom ###
if [ -f  $prefix/custom.cfg ]; then
  source $prefix/custom.cfg;
fi
### END /etc/grub.d/41_custom ###

red.hive · 10-17-2012, 04:22 AM

Hi custangro,

Some news: from what I am told here in this forum and others, the network card problem that I have cannot be solved if I continue to use the trial version of RHEL. I was advised to either move to centos or buy a RHEL license.

Since I will have to re-install the system (probably using centos), can you tell me if there is anything I can do different in the installation process to make the dual boot with two separate drives work without needing to go to the BIOS every time to change boot order?

Thanks in advance,

red.hive