Currently, I've a local Debian mirror for stable/squeeze, and I also have
the up-to-date DVD iso files for this distribution.  See below for detail:

1- The local mirror of debian is located at the following location on my
computer:

werner@debian-asus:~/software/LocalRepo/apt-mirror/mirror/
mirror.bjtu.edu.cn/debian$ ls
dists  pool

2- The DVD iso files for this distribution are located at the following
location on my computer:

werner@debian-asus:~/software/LocalRepo/jigdo/iso-dvd/stable$ ls
debian-6.0.6-amd64-DVD-1.iso  debian-6.0.6-amd64-DVD-5.iso
debian-6.0.6-amd64-DVD-2.iso  debian-6.0.6-amd64-DVD-6.iso
debian-6.0.6-amd64-DVD-3.iso  debian-6.0.6-amd64-DVD-7.iso
debian-6.0.6-amd64-DVD-4.iso  debian-6.0.6-amd64-DVD-8.iso

Now, I want to use these dvd files to update the local mirror of debian,
all of the things need to do is sync the newer files in each dists and
pool directories on the DVD files with the local mirror of debian.  So I
use the following script named rsync_localrepo.sh for this purpose:

werner@debian-asus:~$ cat rsync_localrepo.sh
#!/bin/bash

if [ -d /media/cdrom ]; then  sudo umount /media/cdrom; fi

for i in *iso
do
sudo mount -o loop -t iso9660 /home/werner/software/LocalRepo/jigdo/iso-
dvd/stable/${i} /media/cdrom
rsync -avuP --temp-dir=/tmp /media/cdrom/dists/ /home/werner/software/
LocalRepo/apt-mirror/mirror/mirror.bjtu.edu.cn/debian/dists/
rsync -avuP --temp-dir=/tmp /media/cdrom/pool/ /home/werner/software/
LocalRepo/apt-mirror/mirror/mirror.bjtu.edu.cn/debian/pool/
sudo umount /media/cdrom
done

But, when I run this script, I meet the following issues:

---------------
werner@debian-asus:~$ ./rsync_localrepo.sh
umount: /media/cdrom: not mounted
Usage: mount -V                 : print version
       mount -h                 : print this help
       mount                    : list mounted filesystems
       mount -l                 : idem, including volume labels
So far the informational part. Next the mounting.
The command is `mount [-t fstype] something somewhere'.
Details found in /etc/fstab may be omitted.
       mount -a [-t|-O] ...     : mount all stuff from /etc/fstab
       mount device             : mount device at the known place
       mount directory          : mount known device here
       mount -t type dev dir    : ordinary mount command
Note that one does not really mount a device, one mounts
a filesystem (of the given type) found on the device.
One can also mount an already visible directory tree elsewhere:
       mount --bind olddir newdir
or move a subtree:
       mount --move olddir newdir
One can change the type of mount containing the directory dir:
       mount --make-shared dir
       mount --make-slave dir
       mount --make-private dir
       mount --make-unbindable dir
One can change the type of all the mounts in a mount subtree
containing the directory dir:
       mount --make-rshared dir
       mount --make-rslave dir
       mount --make-rprivate dir
       mount --make-runbindable dir
A device can be given by name, say /dev/hda1 or /dev/cdrom,
or by label, using  -L label  or by uuid, using  -U uuid .
Other options: [-nfFrsvw] [-o options] [-p passwdfd].
For many more details, say  man 8 mount .
sending incremental file list
rsync: change_dir "/media/cdrom/dists" failed: No such file or directory
(2)

sent 12 bytes  received 12 bytes  48.00 bytes/sec
total size is 0  speedup is 0.00
rsync error: some files/attrs were not transferred (see previous errors)
(code 23) at main.c(1060) [sender=3.0.7]
sending incremental file list
rsync: change_dir "/media/cdrom/pool" failed: No such file or directory
(2)

sent 12 bytes  received 12 bytes  48.00 bytes/sec
total size is 0  speedup is 0.00
rsync error: some files/attrs were not transferred (see previous errors)
(code 23) at main.c(1060) [sender=3.0.7]
umount: /media/cdrom: not mounted
---------------

Could someone please give me some hints on these issues?  Thanks in
advance.

Regards

Also, if a filesystem is mounted there's a possibility that it is in
use so umount may fail.

  for i in /home/werner/.../iso-dvd/stable/*iso
  do
    sudo ... "$i" /media/cdrom

In the absence of any matches for *iso in $PWD, $i will be '*iso' in the
loop.  Parameter expansion would then give:

  sudo mount -o loop -t iso9660 /home/.../stable/*iso /media/cdrom

Finally globbing, which would take place due to $i *NOT* *BEING* *QUOTED,*
would result in the shell invoking mount with a list of all the files
matching *iso in the .../stable/ directory:

  sudo mount -o loop -t iso9660  \
       /home/.../stable/debian-6.0.6-amd64-DVD-1.iso \
       /home/.../stable/debian-6.0.6-amd64-DVD-2.iso \
       /home/.../stable/debian-6.0.6-amd64-DVD-3.iso \
       /home/.../stable/debian-6.0.6-amd64-DVD-4.iso \
       /home/.../stable/debian-6.0.6-amd64-DVD-5.iso \
       /home/.../stable/debian-6.0.6-amd64-DVD-6.iso \
       /home/.../stable/debian-6.0.6-amd64-DVD-7.iso \
       /home/.../stable/debian-6.0.6-amd64-DVD-8.iso \
       /media/cdrom

The remaining errors are a consequence of the mount failure.

Untested.

#! /bin/sh -

repo=$HOME/software/LocalRepo

isodir=$repo/jigdo/iso-dvd/stable

mirror=$repo/apt-mirror/mirror/mirror.bjtu.edu.cn/debian

isomount=/media/cdrom

if mount | grep -q " on $isomount\\>" ; then
  echo "Mount point '$isomount' in use." 1>&2
  exit 1
fi

if [ ! -d "$isodir" ]; then
  echo "Missing DVD filesystem image directory: '$isodir'" 1>&2
  exit 1
fi

mkdir -v -p -- "$mirror" || exit 1

sudo mkdir -v -p -- "$isomount" || exit 1

for i in "$isodir"/*.iso ; do
  if sudo mount -o loop -t iso9660 "$i" "$isomount" ; then
    rsync -avuP --temp-dir=/tmp \
          "$isomount/dists" "$isomount/pool" "$mirror/"
    rc=$?
    # die if can't unmount -- avoid mount heaps.
    sudo umount "$isomount" || exit 1
    # Uncomment next line to treat rsync errors as fatal.
    # [ $rc -eq 0 ] || exit 1
  fi
done

In addition to that, you could try to loop-mount the image into a
subdirectory of /mnt instead of media (which is usually not automatically
managed), but AISB it is far easier to set up a local repository mirror and
only update the packages that are needed by its users.

Running the script's shell with the -x switch should help.  Other than that,
none of this has to do with shell programming.  And BTW, *G*NU is *N*ot
*U*nix.

--
PointedEars

Twitter: @PointedEars2
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

  # ls -l
  total 268404
  drwxr-xr-x 2 lpitcher users      4096 2012-10-26 16:00 kav
  -rw-r--r-- 1 lpitcher users 274565120 2012-05-30 15:17 kav_rescue_10.iso

  # file kav_rescue_10.iso
  kav_rescue_10.iso: ISO 9660 CD-ROM filesystem data UDF filesystem data
  (unknown version, id 'NSR01') 'KRD10                          ' (bootable)

  # ls -l kav
  total 0

  # # ****** Note the order of the mount options below ******

  # mount -t iso9660 -o ro,loop kav_rescue_10.iso kav && echo Success
  Success

  # ls -l kav
  total 4
  dr-xr-xr-x 1 root root 2048 2010-04-16 08:00 boot
  -r-xr-xr-x 1 root root    0 2012-02-07 03:00 livecd
  dr-xr-xr-x 1 root root 2048 2012-02-09 03:00 rescue

  # umount kav && echo Umount succeeded
  Umount succeeded

  # ls -l kav
  total 0

The mount above follows the 4th format of the mount(8) command shown in the
SYNOPSIS

  MOUNT(8)           Linux Programmer's Manual                  MOUNT(8)

  NAME
         mount - mount a file system

  SYNOPSIS
         mount [-lhV]

         mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
         mount [-fnrsvw] [-o options [,...]] device | dir
         mount [-fnrsvw] [-t vfstype] [-o options] device dir

[snip]

--
Lew Pitcher
"In Skills, We Trust"

$ mount --version
mount from util-linux 2.20.1 (with libblkid and selinux support)

it works on GNU/Linux with options in either order indeed (as it should).  
However, something *is* wrong here with the way the OP's mount(8) is
invoked, else it would not have displayed its command-line help.

--
PointedEars

Twitter: @PointedEars2
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

Thanks a lot, in fact, I've solved this issue by using the -x option
within bash.  

Regards