[SOLVED] how to boot into linux rescue mode using live CD

General support questions including new installations

[SOLVED] how to boot into linux rescue mode using live CD

Postby rioguia » 2010/10/16 05:12:52

I am attempting to work with adding a new hard drive with a default logical volume setup. In order to complete the task, I am instructed to use a live CD to boot the system without mounting the drives using linux rescue. I am using CentOS-5.5-i386-LiveCD-Release2.iso

I have reviewed the centos documentation. When the live CD boots, it starts a count down to an automatic boot. I attempt to invoke the boot options as directed by hitting the tab and adding the words

linux rescue

at the end of the line and hit return to begin the booting process.

Unfortunately, the linux rescue boot option is ignored and the system mounts the hard drive. Additionally, I have checked the boot option several times by hitting the tab a second time and the option is not displayed.

In researching the issue, I inevitably get very similar instructions like:

The first centos CD or DVD has a rescue mode, just type on the boot screen: linux rescue


Unfortunately, I have not been able to make this work. Can someone take me through the linux rescue procedure step by step?
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Re: how to boot into linux rescue mode using live CD

Postby markkuk » 2010/10/16 12:11:29

Rescue mode is accessible from the installation media (CD#1 or DVD) just as the documentation says. The LiveCD isn't an installation disc and it doesn't support rescue mode.
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Re: how to boot into linux rescue mode using live CD

Postby pschaff » 2010/10/16 13:53:36

The LiveCD does have a large set if tools. If the instructions call for not mounting the disks in rescue mode, then the LiveCD may well be usable for your purposes if you just boot it normally, log in, and "su -" in a terminal to become root. If you want help with that you need to tell us exactly what you are attempting to do.
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Re: how to boot into linux rescue mode using live CD

Postby rioguia » 2010/10/16 16:25:22

Thanks for your help. I did download the latest install disk and the linux rescue worked fine. I was trying to add a new hard drive to a logical volume group.

Prior to posting my question I added a clean 80GB hard drive. Then I

made sure that the new hard drive was found:
dmesg | grep drive

now activating the new hard drive as follows
/sbin/fdisk /dev/hdb

n add a new partition
t change a partition's system id (selected 8e for logical volume)
w write table to disk and exit

/usr/sbin/vgscan --mknodes
/usr/sbin/vgchange -ay
/usr/sbin/lvscan /usr/sbin/lvextend -L+74.5G /dev/VolGroup00/LogVol00

after reboot, made sure the drive was found

/sbin/pvscan

went out and got the correct install CD (instead of the Live CD which doesn't have this feature)

wget ftp://mirror.atlantic.net/pub/centos/5. ... n-1of7.iso

burned the cd
cdrecord -v speed=4 dev=/dev/hdc -eject -pad -dao CentOS-5.5-i386-bin-1of7.iso

rebooted with install CD

when the install disk prompts just run
linux rescue

follow the prompts but say no to mounting the file system when asked.

The rest of the job was easy.

make the volumes available for editing
lvm vgchange -ay

now for some house-keeping to make sure our drives are ready and have no errors

e2fsck -f /dev/VolGroup00/LogVol00

after waiting a long time for the above check to run the below command to resize the VG:

resize2fs /dev/VolGroup00/LogVol00

reboot

check to make sure we now have that extra 74.5GB available.
df -h

ALL DONE. Thanks to all who posted.
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Re: [SOLVED] how to boot into linux rescue mode using live CD

Postby AlanBartlett » 2010/10/16 16:35:24

Thank you for reporting back with full details of your success.

For posterity, this thread is marked [SOLVED].
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