how to search and delete
 

I know "locate" can be used to search files,
and "rm" can be used to delete files.
My question is how to search a kind of file,
for example, abc.txt in /dev/hda5 and delete all of them?
thank you.

You can search for files recursively, including just files on the same partition using the find command. This also lets you execute a command for each file, which could be rm. See for more.

You will need to specify the mount-point of the partition, not the partition's device-special file; if you don't know where it's mounted then you can find it using

find . -name blabla.txt -exec rm "{}" \;

If you want to use locate, go ahead (just replace find . -name blabla.txt with locate blabla.txt)
But I'd recommend to be very careful with using it, since you can easily accidentaly remove i.e. all the files with *.txt extension using this kind of stuff.

That's why I usually do it with:

locate *something* > file.txt
And them see how file.txt looks like and use some regexps to modify the file to make it a script.
Then chmod u+x file.txt and ./file.txt to execute. Then I know what I'm doing and no surprises occur.