MBR cleaning and Serial port
I’ve not received my RHCE certification for a week. This issue makes me so anxious since this certification is very very important to me. As Red Hat official reply, they will track the examiner to submit me archieve. Yes, I feel confident to pass the difficult exam, but long waiting is hard time.
Install Windows after Linux installation.
Fixed an old problem this week. When I try to install Windows in Linux box which has been install Red Hat Enterprise Linux 4.4, select boot device from CD-ROM, the Windows installation program only shows a few text and system seems to be hang. First, I thinks it is cause by CD corrupt and change another Windows CD, it has the same symptom. I googled with this issue and found nothing userful. Last time I had to add second harddisk and install new grub, which took a very long time. When thinking of this, perhaps it’s causes by MBR locked. Hmm, things come to easy. “dd if=/dev/zero of=/dev/hda bs=1024 count=512” to clear all MBR information on the harddisk. Of course original Linux is not able to start again for missing MBR info, but now, Windows operating system would be installed successfully. According to the fixing process, MBR stores operating system boot info and partition table in the first 512 byte of harddisk. It is effective to clear MBR in order to get pure environment.
Connect Linux boxes with Serial port
During tuning kernel, we need to check information when system boots. For example, there’re two Linux machines,
192.168.123.143
192.168.123.67
We want to redirect all 143 information to 67. This could be done by following steps:
1. Login 143, modify /boot/grub/grub.conf
title 2.6.19
root (hd0,0)
kernel /vmlinuz-2.6.19 ro root=LABEL=/1 console=ttyS0,19200
initrd /initrd-2.6.19.img
2. Also in 143, modify /etc/inittab, add the marked line.
# Run gettys in standard runlevels
S0:2345:respawn:/sbin/agetty -L 19200 ttyS0 vt100
3. Restart 143, press DEL to enter CMOS setting,
Console Redirect —- 19200, VT100, COM1, Enabled.
4. Login 67, run minicom program,
# minicom
CTRL+A – Z – O – minicom setting – Serial Port – 19200 8IN 1, ttyS0
Save as default setting and restart minicom.
# minicom -C /root/kernel.log
At this point, you would see all the information of 143 and save the output to /root/kernel.log.