houck@m.cs.uiuc.edu (Chris Houck) (06/20/91)
I was following the suggestions posted here recently about using spare 'a' partitions to hold backup copies of / So I did a dd from rz0a to rz1a and, of course, clobbered the paritioning for disk rz1 (it was a different size + had more partitions) So, doing a 'chpt -q rz1' gives me the partition table for rz0 rather than the one I set up for rz1. I can still access all of the partitions on rz1 and df gives the proper filesystem sizes, so the correct data is in the kernel somewhere. How can I flush it out to the disk? Thanks -Chris (houck@biobio.cs.uiuc.edu)
mjr@hussar.dco.dec.com (Marcus J. Ranum) (06/20/91)
houck@m.cs.uiuc.edu (Chris Houck) writes: > >So, doing a 'chpt -q rz1' gives me the partition table for rz0 rather than the >one I set up for rz1. Well, if you used the default partition map, you could try blasting another copy back onto the disk with 'chpt -d' - if not, it's probably faster to just dump/restore, especially if you can do the dump/restore to disk on some other drive. mjr. -- THIS IS A DISCLAIMER. That's because there is always some IDIOT out there who sees a posting by me, gets the idea that I have an inside line on corporate policy, and gets bent out of shape. If you can figure out how someone smart enough to slobber on a keyboard can make such a leap of faith, please tell me.
grr@cbmvax.commodore.com (George Robbins) (06/20/91)
In article <1991Jun19.221738.4983@m.cs.uiuc.edu> houck@m.cs.uiuc.edu (Chris Houck) writes: > > I was following the suggestions posted here recently about using spare 'a' > partitions to hold backup copies of / So I did a dd from rz0a to rz1a > and, of course, clobbered the paritioning for disk rz1 (it was a different > size + had more partitions) Ouch, you gotta watch that. dd'ing "a" or "c" involves risks of overwriting patitition tables and/or bad block areas (antiquity). dd'ing a is ok when the two disks are of the same nature and parititioning. > So, doing a 'chpt -q rz1' gives me the partition table for rz0 rather than the > one I set up for rz1. I can still access all of the partitions on rz1 and > df gives the proper filesystem sizes, so the correct data is in the kernel somewhere. > How can I flush it out to the disk? Try chpt -a, it appears that it writes the working parition table back onto the disk. If this fails you simply chpt the individual partitions back to where they were. Hopefully, the modified partiting is written down somewhere, else it can be really painful trying to reconstruct your thinking... -- George Robbins - now working for, uucp: {uunet|pyramid|rutgers}!cbmvax!grr but no way officially representing: domain: grr@cbmvax.commodore.com Commodore, Engineering Department phone: 215-431-9349 (only by moonlite)
ian@sibyl.eleceng.ua.OZ (Ian Dall) (06/25/91)
In article <22595@cbmvax.commodore.com> grr@cbmvax.commodore.com (George Robbins) writes: >In article <1991Jun19.221738.4983@m.cs.uiuc.edu> houck@m.cs.uiuc.edu (Chris Houck) writes: >> >> So I did a dd from rz0a to rz1a >> and, of course, clobbered the paritioning for disk rz1 (it was a different >> size + had more partitions) > >Ouch, you gotta watch that. dd'ing "a" or "c" involves risks of overwriting >patitition tables and/or bad block areas (antiquity). Which is one of the reasons I think sticking the partition information in the super block sucks. It is a *bit* better than having it built into the kernel sevice driver, but that is not the only alternative. On a System V box I am familiar with (could be common in the sysV world for all I know) the disk partition information is kept in the first two blocks of the (physical) disk. By convention the partition table defines those two blocks as being a partition (6) so that a program (dpart like chpt) can get at the partition table to modify it. The advantages of this scheme are: 1) You can use dd to make copies of all your partition tables in ordinary files. Keep these files on more than one disk and you should always be able to restore a partition table, even if you have to format at disk. Whilst you can certainly make copies of the superblock, you don't really want to trash other superblock info when you copy it back (or to another disk). 2) There is nothing special about any partition except the one with the two blocks for the partition table in it. You can put swap anywhere except on the 2 block partition containing the partition table. -- Ian Dall I'm not into isms, but hedonism is the most harmless I can think of. -- Phillip Adams ACSnet: ian@sibyl.eleceng.ua.oz internet: ian@sibyl.eleceng.ua.oz.au