55 lines
2.4 KiB
Plaintext
55 lines
2.4 KiB
Plaintext
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Raw device driver support on SLS 9
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On SLS 9, you will notice that by default, raw devices (nodes) (/dev/rawctl
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and /dev/raw/rawN (1-15)) no longer exist whereas in SLES 8, the raw nodes were
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created when the system was initially installed. SLS 9, by default, uses
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the new dynamic userspace implementation "sysfs" together with "udev" which
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replaces the previous static "dev" system.
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Raw devices are moving towards eventual obsolescence with block+O_DIRECT
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support intended as a replacement. The primary application users of raw
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character devices have been databases so the database you are using will have
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to support the O_DIRECT functionality before moving away from raw character
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devices.
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Using RAW with kernel 2.6 (SLS 9)
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---------------------------------
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Raw device usage in kernel 2.6 together with udev and sysfs was intended to be
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quite seamless. Basically, all that is required is to load the raw module after
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each reboot using the commands "modprobe raw" or "rcraw start". Then use the
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"raw" command to create the bindings to the block character devices. The raw
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device nodes are no longer required to exist before the bindings are assigned
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and used.
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Using a single script, you can you load the raw module and bind the raw nodes
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to block devices.
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#!/usr/bin
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# load the raw module
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modprobe raw # can also use "rcraw start"
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# create the raw bindings
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raw /dev/raw/raw1 /dev/sdb1
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raw /dev/raw/raw2 /dev/sbc1
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You can see if the raw driver is available by issuing "rcraw status". If the
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raw driver is loaded, the command should return a status of "running". A status
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of "dead" will usually indicate that the driver was not loaded or
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the /dev/rawctl file does not exist. The /dev/rawctl file is automatically
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created when the module is loaded. This file and the /dev/raw/rawN nodes can
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also be viewed under the /sys/class/raw directory.
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Raw node permissions
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----------------------------------
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When the raw devices are assigned, permission settings are determined from the
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/etc/udev/udev.permission file. This file can be modified to assign different
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owner, group and/or access permissions to the raw nodes. For example, by
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default, the permission settings for raw nodes are as follows:
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raw/raw*:root:disk:660
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Here, root:disk is the default owner:group with read write access for owner and
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group. As an example, to create the raw nodes with an owner:group of
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user1:group1 and read write access for all, change the assignment as follows:
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raw/raw*:user1:group1:666
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