220 lines
8.7 KiB
Text
220 lines
8.7 KiB
Text
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README file for the osst driver
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===============================
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(w) Kurt Garloff <garloff@suse.de> 12/2000
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This file describes the osst driver as of version 0.8.x/0.9.x, the released
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version of the osst driver.
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It is intended to help advanced users to understand the role of osst and to
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get them started using (and maybe debugging) it.
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It won't address issues like "How do I compile a kernel?" or "How do I load
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a module?", as these are too basic.
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Once the OnStream got merged into the official kernel, the distro makers
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will provide the OnStream support for those who are not familiar with
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hacking their kernels.
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Purpose
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-------
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The osst driver was developed, because the standard SCSI tape driver in
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Linux, st, does not support the OnStream SC-x0 SCSI tape. The st is not to
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blame for that, as the OnStream tape drives do not support the standard SCSI
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command set for Serial Access Storage Devices (SASDs), which basically
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corresponds to the QIC-157 spec.
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Nevertheless, the OnStream tapes are nice pieces of hardware and therefore
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the osst driver has been written to make these tape devs supported by Linux.
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The driver is free software. It's released under the GNU GPL and planned to
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be integrated into the mainstream kernel.
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Implementation
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--------------
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The osst is a new high-level SCSI driver, just like st, sr, sd and sg. It
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can be compiled into the kernel or loaded as a module.
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As it represents a new device, it got assigned a new device node: /dev/osstX
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are character devices with major no 206 and minor numbers like the /dev/stX
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devices. If those are not present, you may create them by calling
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Makedevs.sh as root (see below).
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The driver started being a copy of st and as such, the osst devices'
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behavior looks very much the same as st to the userspace applications.
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History
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-------
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In the first place, osst shared it's identity very much with st. That meant
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that it used the same kernel structures and the same device node as st.
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So you could only have either of them being present in the kernel. This has
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been fixed by registering an own device, now.
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st and osst can coexist, each only accessing the devices it can support by
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themselves.
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Installation
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------------
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osst got integrated into the linux kernel. Select it during kernel
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configuration as module or compile statically into the kernel.
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Compile your kernel and install the modules.
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Now, your osst driver is inside the kernel or available as a module,
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depending on your choice during kernel config. You may still need to create
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the device nodes by calling the Makedevs.sh script (see below) manually,
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unless you use a devfs kernel, where this won't be needed.
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To load your module, you may use the command
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modprobe osst
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as root. dmesg should show you, whether your OnStream tapes have been
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recognized.
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If you want to have the module autoloaded on access to /dev/osst, you may
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add something like
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alias char-major-206 osst
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to your /etc/modprobe.conf (before 2.6: modules.conf).
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You may find it convenient to create a symbolic link
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ln -s nosst0 /dev/tape
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to make programs assuming a default name of /dev/tape more convenient to
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use.
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The device nodes for osst have to be created. Use the Makedevs.sh script
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attached to this file.
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Using it
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--------
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You may use the OnStream tape driver with your standard backup software,
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which may be tar, cpio, amanda, arkeia, BRU, Lone Tar, ...
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by specifying /dev/(n)osst0 as the tape device to use or using the above
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symlink trick. The IOCTLs to control tape operation are also mostly
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supported and you may try the mt (or mt_st) program to jump between
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filemarks, eject the tape, ...
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There's one limitation: You need to use a block size of 32kB.
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(This limitation is worked on and will be fixed in version 0.8.8 of
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this driver.)
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If you just want to get started with standard software, here is an example
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for creating and restoring a full backup:
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# Backup
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tar cvf - / --exclude /proc | buffer -s 32k -m 24M -B -t -o /dev/nosst0
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# Restore
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buffer -s 32k -m 8M -B -t -i /dev/osst0 | tar xvf - -C /
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The buffer command has been used to buffer the data before it goes to the
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tape (or the file system) in order to smooth out the data stream and prevent
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the tape from needing to stop and rewind. The OnStream does have an internal
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buffer and a variable speed which help this, but especially on writing, the
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buffering still proves useful in most cases. It also pads the data to
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guarantees the block size of 32k. (Otherwise you may pass the -b64 option to
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tar.)
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Expect something like 1.8MB/s for the SC-x0 drives and 0.9MB/s for the DI-30.
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The USB drive will give you about 0.7MB/s.
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On a fast machine, you may profit from software data compression (z flag for
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tar).
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USB and IDE
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-----------
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Via the SCSI emulation layers usb-storage and ide-scsi, you can also use the
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osst driver to drive the USB-30 and the DI-30 drives. (Unfortunately, there
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is no such layer for the parallel port, otherwise the DP-30 would work as
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well.) For the USB support, you need the latest 2.4.0-test kernels and the
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latest usb-storage driver from
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http://www.linux-usb.org/
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http://sourceforge.net/cvs/?group_id=3581
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Note that the ide-tape driver as of 1.16f uses a slightly outdated on-tape
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format and therefore is not completely interoperable with osst tapes.
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The ADR-x0 line is fully SCSI-2 compliant and is supported by st, not osst.
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The on-tape format is supposed to be compatible with the one used by osst.
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Feedback and updates
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--------------------
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The driver development is coordinated through a mailing list
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<osst@linux1.onstream.nl>
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a CVS repository and some web pages.
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The tester's pages which contain recent news and updated drivers to download
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can be found on
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http://linux1.onstream.nl/test/
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If you find any problems, please have a look at the tester's page in order
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to see whether the problem is already known and solved. Otherwise, please
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report it to the mailing list. Your feedback is welcome. (This holds also
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for reports of successful usage, of course.)
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In case of trouble, please do always provide the following info:
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* driver and kernel version used (see syslog)
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* driver messages (syslog)
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* SCSI config and OnStream Firmware (/proc/scsi/scsi)
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* description of error. Is it reproducible?
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* software and commands used
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You may subscribe to the mailing list, BTW, it's a majordomo list.
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Status
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------
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0.8.0 was the first widespread BETA release. Since then a lot of reports
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have been sent, but mostly reported success or only minor trouble.
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All the issues have been addressed.
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Check the web pages for more info about the current developments.
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0.9.x is the tree for the 2.3/2.4 kernel.
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Acknowledgments
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----------------
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The driver has been started by making a copy of Kai Makisara's st driver.
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Most of the development has been done by Willem Riede. The presence of the
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userspace program osg (onstreamsg) from Terry Hardie has been rather
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helpful. The same holds for Gadi Oxman's ide-tape support for the DI-30.
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I did add some patches to those drivers as well and coordinated things a
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little bit.
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Note that most of them did mostly spend their spare time for the creation of
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this driver.
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The people from OnStream, especially Jack Bombeeck did support this project
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and always tried to answer HW or FW related questions. Furthermore, he
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pushed the FW developers to do the right things.
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SuSE did support this project by allowing me to work on it during my working
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time for them and by integrating the driver into their distro.
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More people did help by sending useful comments. Sorry to those who have
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been forgotten. Thanks to all the GNU/FSF and Linux developers who made this
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platform such an interesting, nice and stable platform.
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Thanks go to those who tested the drivers and did send useful reports. Your
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help is needed!
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Makedevs.sh
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-----------
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#!/bin/sh
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# Script to create OnStream SC-x0 device nodes (major 206)
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# Usage: Makedevs.sh [nos [path to dev]]
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# $Id: README.osst.kernel,v 1.4 2000/12/20 14:13:15 garloff Exp $
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major=206
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nrs=4
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dir=/dev
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test -z "$1" || nrs=$1
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test -z "$2" || dir=$2
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declare -i nr
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nr=0
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test -d $dir || mkdir -p $dir
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while test $nr -lt $nrs; do
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mknod $dir/osst$nr c $major $nr
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chown 0.disk $dir/osst$nr; chmod 660 $dir/osst$nr;
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mknod $dir/nosst$nr c $major $[nr+128]
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chown 0.disk $dir/nosst$nr; chmod 660 $dir/nosst$nr;
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mknod $dir/osst${nr}l c $major $[nr+32]
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chown 0.disk $dir/osst${nr}l; chmod 660 $dir/osst${nr}l;
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mknod $dir/nosst${nr}l c $major $[nr+160]
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chown 0.disk $dir/nosst${nr}l; chmod 660 $dir/nosst${nr}l;
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mknod $dir/osst${nr}m c $major $[nr+64]
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chown 0.disk $dir/osst${nr}m; chmod 660 $dir/osst${nr}m;
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mknod $dir/nosst${nr}m c $major $[nr+192]
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chown 0.disk $dir/nosst${nr}m; chmod 660 $dir/nosst${nr}m;
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mknod $dir/osst${nr}a c $major $[nr+96]
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chown 0.disk $dir/osst${nr}a; chmod 660 $dir/osst${nr}a;
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mknod $dir/nosst${nr}a c $major $[nr+224]
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chown 0.disk $dir/nosst${nr}a; chmod 660 $dir/nosst${nr}a;
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let nr+=1
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done
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