SysAdmin Valley

There have been times where I’ve installed Linux on a computer and needed to reinstall Windows.  Sometimes I’ve had an issue where after the install gets finished, the installer appears fine but it doesn’t update the MBR (Master Boot Record).  So when you reboot the computer you get a Lilo or Grub error saying that the Linux Operating System that it thinks is install is not there.

Before you reinstall Windows, download any of the bootable Linux distro’s such as Fedora Live, Ubuntu or Knoppix and boot into the temporary Linux.  Then bring up a Linux shell and type the following.  You may need to change hda to your appropriate hard drive device

dd if=/dev/zero of=/dev/hda bs=512 count=1

I do a lot of work with MySQL and I’ve had this reoccuring problem were I need to find some text in a table and replace it with new text. Like say I have a table of data that talks about dogs and I want to replace every occurrence of dog with cat. The old way I would search the entire table to find all rows that have the word dog in it, then that would give me a list to manually update each row. I’d then rerun the query to see if I missed any.

Recently I found that MySQL supports a command called what else but “replace”. So let’s say I have a table called “news” and in the table is a column called “content” and I wanted to replace all references of “dog” with “cat”, here is an example query.

update news set content = replace(content, “dog”, “cat”);

Very simple, it tells MySQL to replace the “content” field with what’s in the “content” field but replace “dog” with “cat”.