On 03/29/2011 10:45 AM, Daniel Taylor wrote: > I would like to be able to break our ext4 file system > (specifically corrupt the journal) to be sure that we > can automatically notice the problem and attempt an > autonomous fix. > > dumpe2fs tells me the inode, but not, that I can see, the > blocks where the journal exists (for "dd"ing junk to it). yeah, AFAICS, you can corrupt it by dd. As for the journal, normally the journal file uses the inode no 8. So use debugfs -R 'stat <8>' /dev/sdx. Then you will get the disk layout of your journal. In my box, it looks as: Inode: 8 Type: regular Mode: 0600 Flags: 0x80000 Generation: 0 Version: 0x00000000:00000000 User: 0 Group: 0 Size: 33554432 File ACL: 0 Directory ACL: 0 Links: 1 Blockcount: 65536 Fragment: Address: 0 Number: 0 Size: 0 ctime: 0x4d86f9ad:00000000 -- Mon Mar 21 15:09:33 2011 atime: 0x4d86f9ad:00000000 -- Mon Mar 21 15:09:33 2011 mtime: 0x4d86f9ad:00000000 -- Mon Mar 21 15:09:33 2011 crtime: 0x4d86f9ad:00000000 -- Mon Mar 21 15:09:33 2011 Size of extra inode fields: 28 EXTENTS: (0-8191): 131072-139263 So see, you get the file's physical block number of that file 131072-139263. Now corrupt the file as you wish with dd. ;) Regards, Tao -- 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
