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J. van der Knaap
*nix forums beginner
Joined: 07 Feb 2005
Posts: 2
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 Posted: Mon Feb 07, 2005 7:48 pm Post subject:
mount_nullfs question
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I mean to run an ftp server that uses ftpchroot, restricting all users
to the root of their homedirs. However all users should have access to
some dirs that are outside their root. I thought I might get there by
using symbolic links, but that doesn't quite seem to work with an
ftpchroot-ed ftpd, especially when the public dirs are not on the same
slice.
It's been suggested I try mount_nullfs to mount dirs outside user's
root/homedir to points inside their homedir. This does work.
However the manpages of mount_nullfs displays a rather ominous bug warning:
THIS FILE SYSTEM TYPE IS NOT YET FULLY SUPPORTED (READ: IT DOESN'T WORK)
AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM. USE AT YOUR OWN
RISK. BEWARE OF DOG. SLIPPERY WHEN WET.
Does anybody here have experiences with mount_nullfs resulting in loss
of data? Under which conditions did/can that occur? Can there be an
educated guess as to the risk I would be running?
Thank you,
Joost |
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Kris Kennaway
*nix forums Guru
Joined: 28 Apr 2002
Posts: 634
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| Posted: Tue Feb 08, 2005 12:00 am Post subject:
Re: mount_nullfs question
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On 2005-02-07, J. van der Knaap <spamzuigt@pastrami.be> wrote:
| Quote: | I mean to run an ftp server that uses ftpchroot, restricting all users
to the root of their homedirs. However all users should have access to
some dirs that are outside their root. I thought I might get there by
using symbolic links, but that doesn't quite seem to work with an
ftpchroot-ed ftpd, especially when the public dirs are not on the same
slice.
It's been suggested I try mount_nullfs to mount dirs outside user's
root/homedir to points inside their homedir. This does work.
However the manpages of mount_nullfs displays a rather ominous bug warning:
THIS FILE SYSTEM TYPE IS NOT YET FULLY SUPPORTED (READ: IT DOESN'T WORK)
AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM. USE AT YOUR OWN
RISK. BEWARE OF DOG. SLIPPERY WHEN WET.
Does anybody here have experiences with mount_nullfs resulting in loss
of data? Under which conditions did/can that occur? Can there be an
educated guess as to the risk I would be running?
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In 5.3 it seems to work, at least in the situations I've used it in
(r/w file storage). What I haven't tested are exotic things like
using sockets on the nullfs lower level, simultaneously mmapping files
on both upper and lower levels, etc. What may happen if you hit a bug
is that your system will panic, and there will be damage to the
filesystem that needs to be repaired by fsck (i.e. associated loss of
files). Give it a try, but make sure you have backup and recovery
procedures in place.
Kris |
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Mike Packard
*nix forums beginner
Joined: 08 Feb 2005
Posts: 5
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| Posted: Tue Feb 08, 2005 2:38 am Post subject:
Re: mount_nullfs question
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Kris Kennaway wrote:
| Quote: | On 2005-02-07, J. van der Knaap <spamzuigt@pastrami.be> wrote:
I mean to run an ftp server that uses ftpchroot, restricting all users
to the root of their homedirs. However all users should have access to
some dirs that are outside their root. I thought I might get there by
using symbolic links, but that doesn't quite seem to work with an
ftpchroot-ed ftpd, especially when the public dirs are not on the same
slice.
It's been suggested I try mount_nullfs to mount dirs outside user's
root/homedir to points inside their homedir. This does work.
However the manpages of mount_nullfs displays a rather ominous bug warning:
THIS FILE SYSTEM TYPE IS NOT YET FULLY SUPPORTED (READ: IT DOESN'T WORK)
AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM. USE AT YOUR OWN
RISK. BEWARE OF DOG. SLIPPERY WHEN WET.
Does anybody here have experiences with mount_nullfs resulting in loss
of data? Under which conditions did/can that occur? Can there be an
educated guess as to the risk I would be running?
In 5.3 it seems to work, at least in the situations I've used it in
(r/w file storage). What I haven't tested are exotic things like
using sockets on the nullfs lower level, simultaneously mmapping files
on both upper and lower levels, etc. What may happen if you hit a bug
is that your system will panic, and there will be damage to the
filesystem that needs to be repaired by fsck (i.e. associated loss of
files). Give it a try, but make sure you have backup and recovery
procedures in place.
Kris
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Kris,
A while ago I did the same thing. Worked fine, but eventually I got
nervous on the exact same statement you quoted. So instead I switch to
NFS. My home dirs are on their own partition, and I allow only local to
mount them (for NFS). Don't run into any problems this way and don't
expect to. I've got enough horses on my machine to never expect any
slowdowns since I'm going through localhost. I would like to run the
null fs though just not gutsy enough to.
Mike Packard
news@packardshome.net |
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Denis Shaposhnikov
*nix forums beginner
Joined: 08 Feb 2005
Posts: 2
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| Posted: Tue Feb 08, 2005 7:14 am Post subject:
Re: mount_nullfs question
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| Quote: | "J" == J van der Knaap <spamzuigt@pastrami.be> writes:
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J> It's been suggested I try mount_nullfs to mount dirs outside
J> user's root/homedir to points inside their homedir. This does
J> work.
nullfs was very slow in my env (inside jail), try unionfs -r instead.
--
DSS5-RIPE DSS-RIPN 2:550/5068@fidonet 2:550/5069@fidonet
mailto:dsh@vlink.ru http://neva.vlink.ru/~dsh/ |
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Kris Kennaway
*nix forums Guru
Joined: 28 Apr 2002
Posts: 634
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| Posted: Tue Feb 08, 2005 11:55 am Post subject:
Re: mount_nullfs question
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On 2005-02-08, Denis Shaposhnikov <dsh@vlink.ru> wrote:
| Quote: | "J" == J van der Knaap <spamzuigt@pastrami.be> writes:
J> It's been suggested I try mount_nullfs to mount dirs outside
J> user's root/homedir to points inside their homedir. This does
J> work.
nullfs was very slow in my env (inside jail), try unionfs -r instead.
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unionfs is more likely to blow up in cases like I mentioned.
Kris |
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