Nathan, yeah. I agree. I have submitted a lilo patch to do just that (not allowing itself to install onto a XFS partition). But, it seems there are going to be folks not subscribed to the list that may unknowingly install lilo in that manner. On Mon, 2002-03-25 at 22:56, Nathan Scott wrote: > hi, > > On Mon, Mar 25, 2002 at 09:50:14PM -0600, Derek James Witt wrote: > > Hey all. > > > > I'm going through the kernel source for XFS and I'm trying to find out > > how many superblocks a partition usually has and the maximum it's > > allowed to have. > > There is one superblock at the head of every allocation group. > xfs_info/xfs_db/... will show you how many allocation groups a > filesystem has. There is one primary superblock, in the first > AG (at offset zero); and any number of secondary superblocks - > the number of AGs is a mkfs time option. > > The primary superblock is the one the kernel uses at all times. > The secondary superblocks are usually only written at mkfs time, > and are read by xfs_repair when reconstructing the primary SB. > > > So far in xfs_mount.h, I'm seeing that we are allowed > > two superblocks. I am proposing that we have two consecutive primary > > superblocks (duplicates) in use. In other words, mirrored blocks. > > I'll leave it for others to judge the relative merits of this, > my first thought is that it seems overly complex when the answer > should be "don't overwrite the SB in the first place". > > > So, if lilo or any other boot loader comes along and overwrites a part > > of the first superblock, the mounting code can still get at the 2nd sb. > > I think the operational model here should remain "run xfs_repair" > once you've blown your foot off... but, just my 2c. > > > But, the problem is that the size of the superblock I've seen varies > > from 512 bytes to 65535 bytes. In lilo's sources, we got blocks of size > > 1024 and sector sizes of 512. Any ideas on what to do on this? > > The XFS superblock fits within 512 bytes. > > cheers. > > -- > Nathan > -- ** Derek J Witt ** * Email: mailto:djw@flinthills.com * * Home Page: http://www.flinthills.com/~djw/ * *** "...and on the eighth day, God met Bill Gates." - Unknown **
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