[daip] Re: BA048 (fwd)

[Patrick P Murphy]

On Wed, 26 Mar 2003 13:21:28 +0000 (GMT), Pedro Manuel Augusto
   <augusto at uma.pt> said: 

> [root at augusto /]# df -kl /mnt/dados/AUGUSTO_1/
> Filesystem           1K-blocks      Used Available Use% Mounted on
> /dev/hda9             28886768   1119680  27767088   4% /mnt/dados

Fair enough; it's local (the filesystem isn't NFS, it's an IDE disk).

> [root at augusto /]# mount | grep /mnt/dados
> /dev/hda9 on /mnt/dados type vfat (rw,umask=0)

Type VFAT: it's a windows filesystem.  This is part (or maybe all) of the
problem.  VFAT files cannot support normal unix permissions.  In addition,
the filesystem is not mounted with a uid= option; see the man page for
mount, under "Mount options for fat":

       (Note: fat is not a separate filesystem, but a common part of the
       msdos, umsdos and vfat filesystems.)

       uid=value and gid=value
              Set the owner and group of all files. (Default: the uid and
              gid of the current process.)

Because they're not specified, they default to root.  If you have an aips
user, you might want to mount that filesystem as uid=nnn where nnn is the
numeric UID for the aips account.  But there are other problems:

> [root at augusto /]# id -a
> uid=0(root) gid=0(root)
> groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),100(users)
> [root at augusto /]# ls -la /mnt/dados/AUGUSTO_1/
> total 91888
> drwxrwxrwx    2 root     root        81920 Mar 25 10:58 ./
> drwxrwxrwx    7 root     root        16384 Jan  1  1970 ../
> -rwxrwxrwx    1 root     root         8192 Mar 25 10:36 AGD002001.05K;*
> -rwxrwxrwx    1 root     root        10240 Mar 25 10:38 AND002001.05K;*

<snip>

This I don't understand.  The permissions are set so that anyone can do
anything to the directory (./) and the files.  But you couldn't delete
them. 

I suspect something to do with the VFAT file system is at fault here.  If
the actual filesystem is NTFS, that could be it.  There are, or were,
issues with Linux being able to write to such disks.  If it's an old
fashioned FAT filesystem (your windows experts will understand the
difference) then the uid= option and read/write access from Linux will
work fine.  It may be that for your version of Linux, accessing a NTFS
filesystem as VFAT may *appear* to be read/write, but is in fact readonly.

There's the possibility that things could clear up if you edited
/etc/fstab (as root) to change the mount type to "ntfs".  This appears to
be supported in my Red Hat 8.0 system (but I don't run windows [almost
ever] so I don't have any NTFS filesystems to check this against.

The best solution would be to back up the files, convert the filesystem to
EXT2 or EXT3, and restore them (and I realize this poses problems).  AIPS
assumes a normal unix filesystem underneath everything, one that obeys the
usual conventions of file user and group permissions, and NTFS mounted as
a VFAT filesystem does not fit this definition.  I would not recommend
using a NTFS or VFAT or FAT filesystem in production mode as an AIPS disk.

				- Pat