On Thu, Aug 23, 2012 at 07:43:29PM +0530, Prashant Shah wrote: > > We wrote a small tool to dump file inode information from ext2/3 > partition as an assignment related to learning about file systems. > > https://github.com/prashants/tools/tree/master/ext > https://github.com/prashants/tools/blob/master/ext/ext3dump.c > > I am not sure if there is any future use for it other than for > learning purposes. I hope it was enjoyable learning how to access an ext2/3 filesystem directly! Some comments about your code: *) It requires that the file system be mounted (so you can get the inode number), and then it accesses the file directly through the block device. This is a no-no, since the block might not have been flushed out to disk yet if it was a newly created file. *) You don't check that the inode number that you got by using open()/stat() is from the same file system that you are accessing via the block device. *) You don't check to see if the filesystem feature flags are as you expect; this utility will blow up pretty spectacularly on an ext4 file system. If you want to see how a better version of this functionality can be built, please see the "debugfs" program which is part of e2fsprogs. It uses the libext2fs libraries, and is a much more robust program for direct access to a file system via the block device for debugging purposes. If you want to see a more user-friendly interface, please take a look at the e2tools package. It also uses the libext2fs library which is distributed as part of e2fsprogs (and installed on pretty much all Linux distributions), and is a more polished way of accessing a file directly meant to be used by end users --- as opposed to debugfs, which is really meant for file system engineers. So debugfs is more powerful, but you can also do severe harm to the file system if you open the filesystem read/write and you start messing with it. At the same time, debugfs is also a more interesting if you are a student who wants to get a much better understanding of the underlying file system format. Regards, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
