An Oracle blog – Amardeep Sidhu

One of my friend today asked me about removing Linux partitions & GRUB (from a dual boot system) and return back to windows alone. Removing Linux involves just formatting/removing the partitions. Now to remove GRUB either do fdisk /mbr from a Windows 98 bootable CD or do fixmbr after booting into repair mode with Windows XP CD. But if you have none then to remove GRUB you will need some utility like this one and if you reboot before doing that it might make GRUB unable to boot into Windows. It will get stuck at GRUB> prompt only. So there is an option: to manually boot the OS you want (ie Windows). A quick search gave link to this thread. It involves few commands on the GRUB prompt:

grub> rootnoverify (hd0,0)
grub> makeactive
grub> chainloader +1
grub> boot

It will load the NTLDR where your Windows is installed in Partition 1 on HDD 1.

Last week I attended a training on AIX system administration from IBM (organized by company, obviously It was a 7 days course covering all of the system administration stuff. There was a lot of new stuff to learn, LVM being the most number of times uttered word, once we did the chapter on LVM. It was a nice experience as a whole as for the first time I attended any training on Unix.

The sessions (specially after lunch) were sleepy also. I find this ppt method of training pretty boring. The trainer (most of) strictly, stupidly follows the slides and slide, I feel is a dumb sort of thing, makes you feel sleepy except at the moments when there are few eye opening bullet points.

There should be bare minimum number of slides and for rest of the things, trainer should use white board so that everybody follows that and doesn’t sleep

Anyways it was really enjoying to be familiar with so many things in Unix.

Sidhu

I was searching for some good tutorials on awk. Found a very nice (brilliant indeed) article on Oracle website by Emmett Dulaney. A very good introduction for beginners. I searched for some other links as well. Have a read:

1. AWK: The Linux Administrators’ Wisdom Kit

2. A Guided Tour Of Awk

3. AWK Programming

4. UNIX Utilities – awk

Happy awk’ing

Sidhu

I have been installing Linux for last 6 years and for more than half the number of times, came across a message something like “This partitions is beyond the 1024 cylinder boundary and may not be bootable”. But never cared for it much and understood what exactly it meant to say ?

Yesterday I was reading System Admin guide to Linux by Lars Wirzenius (Thanks Howard for the link From there I came to know what exactly that message meant. Quoting from the guide itself:

Unfortunately, the BIOS has a design limitation, which makes it impossible to specify a track number that is larger than 1024 in the CMOS RAM, which is too little for a large hard disk. To overcome this, the hard disk controller lies about the geometry, and translates the addresses given by the computer into something that fits reality. For example, a hard disk might have 8 heads, 2048 tracks, and 35 sectors per track. Its controller could lie to the computer and claim that it has 16 heads, 1024 tracks, and 35 sectors per track, thus not exceeding the limit on tracks, and translates the address that the computer gives it by halving the head number, and doubling the track number. The mathematics can be more complicated in reality, because the numbers are not as nice as here (but again, the details are not relevant for understanding the principle). This translation distorts the operating system’s view of how the disk is organized, thus making it impractical to use the all-data-on-one-cylinder trick to boost performance.
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When using IDE disks, the boot partition (the partition with the bootable kernel image files) must be completely within the first 1024 cylinders. This is because the disk is used via the BIOS during boot (before the system goes into protected mode), and BIOS can’t handle more than 1024 cylinders. It is sometimes possible to use a boot partition that is only partly within the first 1024 cylinders. This works as long as all the files that are read with the BIOS are within the first 1024 cylinders. Since this is difficult to arrange, it is a very bad idea to do it; you never know when a kernel update or disk defragmentation will result in an unbootable system. Therefore, make sure your boot partition is completely within the first 1024 cylinders.

Hope it clears the logic why Linux cries about 1024 cylinder issue at the time of installation.

You can read the guide online from the link above and download the pdf here. Its simple and concise and just too good. Small thing covering much

Sidhu