Attachment 35506 Details for Bug 57298 – file.diff

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file.diff (text/plain), 18.12 KB, created by Dan Pelleg on 2003-09-27 23:20:11 UTC

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Created: 2003-09-27 23:20:11 UTC

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>--- en_US.ISO8859-1/books/handbook/multimedia/chapter.sgml.orig	Fri Sep 26 20:33:58 2003
>+++ en_US.ISO8859-1/books/handbook/multimedia/chapter.sgml	Sat Sep 27 18:03:44 2003
>@@ -1409,4 +1409,382 @@
> 
>   </sect2>
>  </sect1>
>+
>+ <sect1 id="removable-media">
>+  <sect1info>
>+    <authorgroup>
>+      <author>
>+        <firstname>Dan</firstname>
>+	<surname>Pelleg</surname>
>+	<contrib>Contributed by </contrib>
>+      </author>
>+      
>+    </authorgroup>
>+    
>+  </sect1info>
>+
>+    <title>Using Removable Memory Devices</title>
>+
>+      <para>Many consumer electronic devices now support removable memory
>+        cards.  They provide a fast and easy way to transfer information to
>+        and from a PC.  Here we explore the ways to use those cards under
>+        &os;.  Our goal is to minimize the administrative overhead for the
>+        user - eliminating the need for <username>root</username> access or
>+        manual mounts.  For simple tasks such as uploading files from the
>+        card we can even come up with a completely hands-off operation -
>+        the user doesn't have to do anything but insert the card in, wait
>+        for a while, and then pop it back out.</para>
>+
>+      <sect2 id="cf-intro">
>+        <title>Introduction</title>
>+
>+        <para>The discussion refers to Compact Flash (CF) cards. However,
>+          most of the instructions also apply, with slight modifications,
>+          to other types of 'flash' media (SmartMedia, MMC, MemoryStick and
>+          all their variations), as well as cameras, MP3 players, and other
>+          devices supported by the &man.umass.4 device driver.  </para>
>+
>+        <para>Compact Flash cards typically interface to a PC in one of
>+          two ways: an external USB card-reader, or through the PC-CARD
>+          (also known as "PCMCIA") slot.  For the PC-CARD case, a cheap
>+          adapter allows insertion of CF media to a standard PC-CARD slot.
>+          Some laptops have a special CF slot, eliminating the need for an
>+          adapter.  The way &os; accesses your device will vary, depending
>+          on the reader type.  PC-CARD readers will show up as ATA disks,
>+          while USB readers will show up as SCSI disks.</para>
>+
>+        <para>Once the "disks" show up, we can mount the filesystem on
>+          them, and then manipulate it in the standard way - copying and
>+          deleting files.  We explore two approaches to doing this.  The
>+          first involves a script that handles the specific task of
>+          uploading all of the new files from the CF card to the PC,
>+          requiring no user intervention.  The second is more general, and
>+          uses the automounter to mount the filesystem as soon as it is
>+          accessed, letting the user directly manipulate it.  </para>
>+
>+        <para>To make things easy to follow, we first detail the steps
>+          for USB readers, and then explain how the same procedures work
>+          for PC-CARD devices.</para>
>+
>+        </sect2>
>+        <sect2 id="cf-usb">
>+          <title>USB-Based Compact-Flash Readers</title>
>+            <sect3>
>+              <title>Requirements</title>
>+
>+                <para>Support for USB readers requires the &man.umass.4
>+                  driver.  As the manpage tells you, you will need the
>+                  following options in your kernel config: </para>
>+
>+                <programlisting>device usb
>+device ohci (OR device uhci)
>+device umass
>+device scbus
>+device da
>+device pass</programlisting>
>+
>+                <para>Note that the GENERIC kernel that comes with 4.8
>+                  already includes them all.  After recompiling your kernel
>+                  (or not, if you're using GENERIC), you should be able to
>+                  plug the reader into the USB slot and have it show up.
>+                  Usually, the media has to be already in the reader before
>+                  you plug in the USB connector.  So, if things don't work
>+                  for you, unplug the reader from the USB slot, stick the
>+                  memory card in, and plug it into USB again.</para>
>+
>+                <para>The message log will tell you the device name for
>+                  the CF card.  <devicename>umass</devicename>-attached
>+                  devices will show up like this:</para>
>+
>+                <screen>da0 at umass-sim0 bus 0 target 0 lun 0</screen>
>+
>+                <para>indicating that the device name is
>+                  <devicename>da0</devicename>.  Note that if you already
>+                  have SCSI devices in the system, this might interfere
>+                  with whatever you have in &man.fstab.5;.  To avoid nasty
>+                  surprises, you should wire down all of your other SCSI
>+                  devices so their numbering doesn't change.</para>
>+
>+                <para>If the reader is supported, at this point you
>+                  should be able to mount the device.  If you are using a
>+                  card from a standard camera or music player, the
>+                  following command, typed as root, will mount it under
>+                  <filename class="directory">/mnt</filename>:</para>
>+
>+                <screen>&prompt.root; <userinput>mount -t msdos /dev/da0s1 /mnt</userinput></screen>
>+
>+                <para>In theory, at this point you can become
>+                  <username>root</username> whenever you want and
>+                  <command>mount</command> the device.  However the goal
>+                  here is to try and avoid this step.  The following
>+                  section and <xref linkend="cf-automount"> describe two
>+                  different strategies that accomplish this.</para>
>+
>+              </sect3>
>+              <sect3>
>+                <title>Using an upload script</title>
>+
>+                <para>Most often, the computer is used as a backing store
>+                  for the small-capacity CF card.  You take a few photos on
>+                  your digital camera, and want to make sure you have
>+                  copied them to a "real" disk so you can later process
>+                  them.  We use a script that uploads all the new photos
>+                  from a CF card into the PC's disk-drive.  Once installed,
>+                  it will go into action as soon as the CF media is
>+                  attached.  It will <command>mount</command> the
>+                  filesystem, copy the new files over, and then unmount it.
>+                  The only thing the user has to do is insert the media and
>+                  later pull it out.</para>
>+
>+                <para>You can <link linkend="cf-script">download a copy of the
>+                  script</link>.  We assume you have it installed at
>+                  <filename>/usr/local/sbin/copy-flash</filename> and
>+                  marked it as executable.</para>
>+
>+                <para>Next, you will need the USB daemon, &man.usbd.8;.
>+                  Add this line to <filename>/etc/rc.conf</filename>,
>+                  unless it's already there:</para>
>+
>+                <programlisting>usbd_enable="YES"</programlisting>
>+
>+                <para>To make the script run when a USB reader is
>+                  attached, add an entry to
>+                  <filename>/etc/usbd.conf</filename>.  It will look like
>+                  this:</para>
>+
>+                <programlisting>device "CF card"
>+devname "umass[0-9]+"
>+attach "/usr/local/sbin/copy-flash da0 /tmp/cf <replaceable>CFOWNER</replaceable>"</programlisting>
>+
>+                <para>where <devicename>da0</devicename> should be
>+                  substituted by whatever device you see in the message
>+                  log.  Before you use this hook, replace the string
>+                  CFOWNER.  It should be a user name, and the copied files
>+                  will be owned by that user.  This is normally you or the
>+                  primary user of the machine.  Also, create the target
>+                  directory into which the files will be copied.  In this
>+                  example it is <filename
>+                  class="directory">/tmp/cf</filename>.  Make sure you
>+                  choose a partition that is big enough to contain all the
>+                  files you plan on using.  Finally, don't forget to kill
>+                  and restart <command>usbd</command>.</para>
>+
>+                <para>The provided script will also sound a short melody
>+                  once the copying is done.  This lets you know it is safe
>+                  to pull out the CF card.  If you don't hear it, add the
>+                  &man.spkr.4 psuedo-device to your kernel.</para>
>+
>+              </sect3>
>+            </sect2>
>+            <sect2 id="cf-pccard">
>+              <title>PC-CARD readers</title>
>+
>+                <para>This section repeats the previous one, this time
>+                  explaining how to make a PC-CARD slot (or a dedicated CF
>+                  slot) work.</para>
>+
>+              <sect3>
>+                <title>Requirements</title>
>+
>+                  <para>Compared to USB readers, PC-CARD readers are
>+                    simpler.  They only require the &man.pccardd.8 daemon
>+                    to run.  In all likelihood, you already have it.  If
>+                    not, add the following line to
>+                    <filename>/etc/rc.conf</filename>:</para>
>+
>+                  <programlisting>pccard_enable="YES"</programlisting>
>+
>+                  <para>Again, the message log will tell us the name of
>+                    the device.  For example, one
>+                    <command>pccardd</command>-attached device shows up
>+                    as:</para>
>+
>+                    <screen>ad8: 124MB &lt;SAMSUNG CF/ATA&gt; [496/16/32] at ata4-master BIOSPIO</screen>
>+
>+                    <para>indicating that the device is <devicename>ad8</devicename>.</para>
>+
>+              </sect3>
>+              <sect3>
>+                <title>Using an upload script</title>
>+
>+                  <para>The <link linkend="cf-script">same script as
>+                    above</link> can be used for PC-CARD readers.  The only
>+                    difference is what runs it - in this case, it is
>+                    <command>pccardd</command> instead of
>+                    <command>usbd</command>.  Add this entry to
>+                    <filename>/etc/pccardd.conf</filename> (create the file
>+                    if it doesn't exist on your system):</para>
>+
>+                    <programlisting># GENERIC Flash ATA / ATA HDD
>+	generic fixed_disk
>+		config  0x1 "ata" ?
>+		insert /usr/local/sbin/copy-flash $device /tmp/cf <replaceable>CFOWNER</replaceable>
>+		logstr  "GENERIC Flash ATA / ATA HDD"</programlisting>
>+
>+                  <para>Again, change CFOWNER to the name of the user you
>+                    want to have access to the files.</para>
>+              </sect3>
>+            </sect2>
>+            <sect2 id="cf-automount">
>+              <title>Using the automounter</title>
>+
>+                <para>Much of the information in this section is from a
>+                  <ulink url="http://www.daemonnews.org/200202/automounting.html">
>+                  Dæmon News article by Renaud Waldura </ulink>.  The
>+                  automounter can mount filesystems automatically whenever
>+                  they are accessed.  That is, you simply
>+                  <command>ls</command> or <command>cd</command> to a
>+                  directory that represents a filesystem, and the
>+                  automounter intercepts the operation, and makes sure the
>+                  underlying filesystem is mounted.  It is typically used
>+                  for managing NFS mounts, but here we use it for local
>+                  mounts.</para>
>+
>+                <para>Add these lines to <filename>/etc/amd.map</filename>:</para>
>+
>+                <programlisting>localhost		type:=auto;fs:=${map};pref:=${key}/
>+
>+localhost/cf            type:=program;fs:=/mnt/cf;\
>+    mount:="/sbin/mount mount /mnt/cf";\
>+    unmount:="/sbin/umount umount /mnt/cf"</programlisting>
>+
>+                <para>Next, add a line for the filesystem in
>+                  <filename>/etc/fstab</filename>.  It will look like this,
>+                  assuming that in your system the reader appears as the
>+                  device <filename>/dev/ad8</filename>:</para>
>+
>+<programlisting>/dev/ad8s1  /mnt/cf  msdos  rw,noauto  0  0</programlisting>
>+
>+                <para>Note that we specify the first slice on the disk,
>+                  and the <option>msdos</option> filesystem.  Many digital
>+                  cameras expect their CF cards to be configured in this
>+                  way.  We also need to create the mount point:</para>
>+
>+                  <screen>&prompt.root; <userinput>mkdir -p /mnt/cf</userinput></screen>
>+
>+                <para>To enable the automounter, add this line to
>+                  <filename>/etc/rc.conf</filename>:</para>
>+
>+                <programlisting>portmap_enable=YES
>+amd_enable="YES"
>+amd_flags="-a /.amd_mnt -l syslog /host /etc/amd.map"</programlisting>
>+
>+                <para>Once you start <command>amd</command> (or reboot),
>+                  any user should be able to access the CF card, simply by
>+                  doing a <command>ls</command> or <command>cd</command> on
>+                  the directory <filename
>+                  class="directory">/host/localhost/cf</filename></para>
>+
>+                <para>Remember that <command>amd</command> only unmounts
>+                  the filesystem after it has been idle for some time.
>+                  This means that before you take the CF card out of the
>+                  slot, you need to stop using it (remembering to
>+                  <command>cd</command> out of any directories on it), and
>+                  wait.  Pulling out a mounted device can cause all kinds
>+                  of trouble, including data loss and system crashes.  So
>+                  you want to make sure you unmount first.  If you're in a
>+                  hurry and can't wait for <command>amd</command> to time
>+                  out, you can ask it to unmount the filesystem immediately
>+                  by doing:</para>
>+
>+<screen>&prompt.user; <userinput>amq -u /host/localhost/cf</userinput></screen>
>+
>+                <para>This, again, is not a privileged operation and does
>+                  not require <username>root</username> access.</para>
>+
>+            </sect2>
>+            <sect2 id="cf-summary">
>+              <title>Summary</title>
>+
>+                <para>We eliminated the need for root access to read and
>+                  write files stored on CF media.  We can let the
>+                  automounter do the mounting for us, or have a script that
>+                  does all the copying as well.  In fact, both of these
>+                  solutions can co-exist: whenever media is inserted, new
>+                  files are immediately copied over.  If the user later
>+                  wants to access the card and, say, delete some files,
>+                  they can do that and <command>amd</command> will take
>+                  care of mounting.</para>
>+
>+                <para>Once you start using the file-copy script, you will
>+                  probably discover that managing multiple copies of the
>+                  same data is hard.  The original photo is kept on the CF
>+                  card, the script makes another one on your local disk,
>+                  and you will also probably make a final copy in your
>+                  electronic album.  To make room and reduce clutter, you
>+                  will want to delete redundant copies.  It is often
>+                  easiest to do this on the PC where you can easily view
>+                  the photos on a big screen.  The problem is, the files
>+                  will re-appear the next time you pop the CF card in.  One
>+                  solution is to wipe the CF card clean every time you
>+                  insert it.  But it is wiser to give the good photos
>+                  another chance, just in case they get lost.  A trick I
>+                  find useful is to create a text file in the directory
>+                  which stores the files from the CF card, and in that file
>+                  I record the name of each file that I delete from the PC
>+                  copy.  This way, I can also quickly delete the same files
>+                  from the CF card whenever it fills up.</para>
>+
>+            </sect2>
>+            <sect2>
>+              <title>Acknowledgments</title>
>+
>+              <para>Scott Mitchell provided greatly valuable help for
>+                this article.  Thanks to Joshua Schachter and Nadav
>+                Eiron.</para>
>+            </sect2>
>+
>+            <sect2 id="cf-script">
>+              <title>Helper Script for Copying Files from CF Card</title>
>+                <programlisting>#!/bin/sh
>+# Dan Pelleg, March 2003
>+#
>+# copy-flash: mount a compact-flash card, copy the contents over, unmount
>+# usage: copy-flash [flash-device] [target-dir] [user]
>+
>+dev=${1:-da6}
>+tgt=${2:-/tmp/foo}
>+user=${3:-root}
>+
>+[ -e "$tgt" ] || mkdir -p $tgt && chown $user $tgt
>+[ -e /mnt/cf ] || mkdir -p /mnt/cf
>+
>+# figure out if we were called with a device like ad8 or ata4. If it's
>+# the latter, figure out the usable device name
>+case ${dev} in
>+    ata* )
>+        channel=${dev##ata}
>+
>+        if [ -n ${channel} ]; then
>+            realdev=$(atacontrol info $channel | grep ^Master | cut -d " " -f 3)
>+        fi
>+    ;;
>+
>+    ad* | da* )
>+        realdev=${dev}
>+    ;;
>+esac
>+
>+if [ -n "${realdev}" ]; then
>+    # on -CURRENT we might need to wait a bit before the device node appears
>+    if [ ! -e /dev/${realdev} ]; then
>+        sleep 5
>+    fi
>+    # if the slice doesn't yet exist, try to nudge
>+    # things so it does. Might be necessary for some devices
>+    # on -CURRENT
>+    # This mount is not supposed to succeed, but it does
>+    # sometime cause the device node to be created.
>+    if [ ! -e /dev/${realdev}s1 ]; then
>+        mount -t msdos /dev/${realdev} /mnt/cf && umount /mnt/cf
>+    fi
>+    mount -t msdos /dev/${realdev}s1 /mnt/cf && \
>+    su ${user} -c "cp -nRp /mnt/cf/ ${tgt}" ; \
>+    # play a tune to let the user know it's all over
>+    umount /mnt/cf && echo "MLT250o3fc" > /dev/speaker
>+fi</programlisting>
>+
>+            </sect2>
>+
>+  </sect1>
> </chapter>

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