Date: Wed, 24 Apr 1996 19:15:43 -0400 (EDT) From: Dave Chapeskie <dchapes@zeus.leitch.com> To: FreeBSD-hackers@FreeBSD.org Subject: BUG in FreeBSD 2.1R Message-ID: <199604242315.TAA07530@ale.zeus.leitch.com> In-Reply-To: <199604242137.XAA28721@uriah.heep.sax.de>
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>As Seppo Kallio wrote: >> >> If I have >> >> /opt/ftp directory with permissions -rwx----- >> >> Then I mount /opt/ftp /dev/sd1a having -rwxr-xr-x >> >> The /opt/ftp directory is getting the real permissions from the original >> directory definition, but it is SHOWING the permissions the mounted disk >> directory has. > >cd /opt/ftp >pwd > >:-) > >This seems to be a bug with all Unix implementations i've seen so far. >The simplest workaround: since mount points finally always use the >permissions from the mounted resource, do always give them 555 or 755 >permissions. > >-- >cheers, J"org > >joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE >Never trust an operating system you don't have sources for. ;-) This is not a bug. I asked this question a year and a half ago on comp.os.386bsd.questions when pwd started giving me errors and I got the following useful reply. The only thing the system uses the mount point's permissions for is in reading ".." >From: blymn@awadi.com.au (Brett Lymn) Newsgroups: comp.os.386bsd.questions Subject: Re: pwd problem with NFS Date: 05 Sep 1994 06:55:47 GMT Message-ID: <BLYMN.94Sep5162547@mallee.awadi.com.au> At first I was going to just shrug my shoulders and say "I dunno" but after a bit of thought I think I have a theory (It's all mine!!!). The theory goes that though we are used to thinking that a file system "covers up" the underlying mount point. This cannot work for some things. Consider the concept of "..", from the file system point of view there is no ".." because it is the top of the tree. When that file system gets mounted under another one then I suppose some magic is done to point ".." of the mounted file system to the correct i-node of the mount point so that when you do something like "cd .." it works properly. Otherwise you would have the weird situation of doing a "cd .." from the mounted file system and staying where you are - just like you do in /. Now if the permissions of the mount point are such that you cannot read them then you cannot work out what you parent directory is hence the message from ls *but* the permissions you see for the mount point when something is mounted are those for "." of the mounted file system *not* the mount point. Getting everything to work so that you could see the underlying mount permissions without breaking the concept of just having something that looks like one big file system (anyone for VMS style sys$dsk0:[usr.blymn]? .... I thought not ;-) would be - ummmm - challenging. Managing disk storage on a unix system is made a lot easier by the fact you can do things like "hmmmm /var is filling up / a lot - I'll wack another disk on and mount it under /var to fix that" Dave> I wonder how many Dave> people get burned on this one. *Lots* I am on a Sun mailing list and see this problem turn up quite regularly. -- Brett Lymn -- Dave Chapeskie Leitch Technology International Inc. Email: dchapes@zeus.leitch.com
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