Date: Thu, 11 Feb 2010 12:10:46 -0500 From: Pierre-Luc Drouin <pldrouin@pldrouin.net> To: Matthew Seaman <m.seaman@infracaninophile.co.uk> Cc: RW <rwmaillists@googlemail.com>, freebsd-questions@freebsd.org Subject: Re: Memory disk "a la mfsroot"? Message-ID: <4B743A16.9020201@pldrouin.net> In-Reply-To: <4B74283B.1070903@infracaninophile.co.uk> References: <4B7419F5.7050602@pldrouin.net> <4B741E56.8010002@infracaninophile.co.uk> <20100211153925.7b88844d@gumby.homeunix.com> <4B74283B.1070903@infracaninophile.co.uk>
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Matthew Seaman wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 11/02/2010 15:39, RW wrote: > >> On Thu, 11 Feb 2010 15:12:22 +0000 >> Matthew Seaman <m.seaman@infracaninophile.co.uk> wrote: >> > > >>> On 11/02/2010 14:53, Pierre-Luc Drouin wrote: >>> >>> >>>> I would like to know if there is a mount command that allows to >>>> create a memory disk that can be initialized from a file. What I am >>>> looking for is something like mount_mfs -F, but that does not >>>> modify the actual file. I know what I could easily to this by >>>> copying the content of the file to the memory disk, but I am >>>> looking for a solution that can be configured via fstab. >>>> >>> Yes. See mdconfig(8) -- there are examples in there of exactly what >>> you want to do. >>> >> I don't think covers what he is asking for. I think you would need a >> union filsystem that overlays a swap-backed filesystem on top of a >> file-backed filesystem - if that's possible. >> > > Actually, I was thinking more along the lines of mounting a .iso as a > cd9660 filesystem. Which won't muck up the underlying .iso, but only > because it's read-only. You could mount a FFS image read-only in > exactly the same way -- I think there's a 'last mounted on' field in the > backing file image that will be updated if the it is writable (even if > the fs itself is mounted ro) but that's not the right answer either. > > Basically, you're going to have to mount and initialise as two separate > operations as far as I can see. > By this do you mean that I would need to copy the whole content of the read-only filesystem to the memory disk? I looked at the man page for mount_unionfs and there is a big warning saying that it is a bad idea to use it, so I guess I will pass on this solution... What I am trying to do basically is to mount a filesystem from a CD but I want to use a memory disk to allow write operations. I would basically want the filesystem to behave like a regular read-write filesystem, but not have to copy everything into a memory disk. What does "mfs_root" do exactly in the official FreeBSD boot CDs? Does it copy the content of mfsroot.gz into a memory disk? That filesystem is so small that I guess it can be copied without any problem... Thanks! > Cheers, > > Matthew > > - -- > Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard > Flat 3 > PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate > Kent, CT11 9PW > -----BEGIN PGP SIGNATURE----- > Version: GnuPG/MacGPG2 v2.0.14 (Darwin) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ > > iEYEARECAAYFAkt0KDsACgkQ8Mjk52CukIxZaACcCIsHKNBckWDFzRWDJqEH/vVC > Pd4AnRp74n7+Jl+z28VwBEYqpfQmNVJ0 > =lxug > -----END PGP SIGNATURE----- > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" >
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