12. The Linux-2.6 kernel12.1. What is new?
Setting up your system as described above for the Linux-2.4.x
kernels will be perfectly good, but with the Linux-2.6.x kernels
(x = 0, 1, 2, 3 at the time of this writing) much more is possible:
USB Hotplugging of devices has been improved immensely. This
means that it has become possible to attach and remove a
device from the USB port with full cognisance of the
system. If a device is attached, it will show in the /proc
filesystem. Once it is removed, it will not show anymore.
The sysfs system has been
introduced. By using this facility, a very tight grip on
attached devices, their attributes and nodes of attachment
is possible.
Utilities for handling hotplugging have been improved or
became available. With the aid of these it is possible to
easily distinguish between attached devices irrespective of
the order in which they were attached.
12.2. Kernel options
Kernel configuration options are very much the same as described
in Section 5.2. The configuration menu
(# make
menuconfig) has been organized differently
and more systematically. Here are the relevant choices:
12.2.1. Bus options-
Support for hot-pluggable devices (CONFIG_HOTPLUG)
12.2.2. Device drivers-
SCSI device support
-
SCSI device support (CONFIG_SCSI scsi_mod)
-
legacy /proc/scsi support (CONFIG_SCSI_PROC_FS)
-
SCSI disk support (CONFIG_BLK_DEV_SD sd_mod)
-
USB support
-
Support for USB (CONFIG_USB usbcore)
-
USB device filesystem (CONFIG_USB_DEVICEFS)
-
UHCI HCD support (CONFIG_USB_UHCI_HCD uhci_hcd)
-
USB Mass Storage support (CONFIG_USB_STORAGE usb_storage)
12.2.3. File systems-
Second extended (CONFIG_EXT2_FS ext2)
-
DOS/FAT/NT filesystems
-
DOS FAT fs support (CONFIG_FAT_FS fat)
-
MSDOS fs support (CONFIG_MSDOS_FS msdos)
-
VFAT (Windows 95) fs support (CONFIG_VFAT_FS vfat)
-
Pseudo filesystems
-
/proc file system support (CONFIG_PROC_FS)
12.3. Notes
It may be in your interest to consult
Migrating to Linux Kernel 2.6,
but it is not necessary to follow steps that cannot be followed.
12.4. Hotplugging and Naming
In Section 6.2 the situation of two USB
devices plugged in at the same time was discussed. The
difficulty is that it becomes hard for the user to
distinguish the two devices. Progress recently made in the
Linux Hotplug
Project (search for hotplug) and implemented in the
2.6-series of kernels, has made it possible to address this
problem efficiently. For implementation some utilities are
needed:
12.4.1. Installation
The sysfs filesystem is intrinsic to
the Linux-2.6 kernel series. It is used by
udev and
sysfstools to obtain information
about kernel objects (devices, etc.), their attributes
and mutual linkages. Activation is according to the
following procedure:
# cd /
# mkdir sys
# mount -t sysfs none /sys
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If you do ls -F
/sys, a whole directory structure
with entries like block/,
bus/, ... will be shown. You were
successful. The mounting should now be made permanent by
adding the following line to
/etc/fstab:
none /sys sysfs defaults 0 0
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This is installed in one of the usual ways without having
to make special configuration options. Instructions in
the README file are very clear. You should, however,
first make sure that the entry
/usr/local/lib is entered in
/etc/ld.so.conf so that the
libsysfs.so libraries will be
recognisable by the system. After installation, check
that the utilities /usr/local/bin/lsbus
and /usr/local/bin/systool have been
installed. Also check that the libraries mentioned above
have been properly linked in
(ldconfig -p | grep
libsysfs).
Next install the hotplug
scripts. The first thing to do is to check that
hotplugging will work on your system. Do:
less
/proc/sys/kernel/hotplug. The
result should be
/sbin/hotplug. If it is
not so, you should add the line echo
"/sbin/hotplug" > /proc/sys/kernel/hotplug to
an appropriate initialization script,
e.g. /etc/rc.d/rc.local. This
command could also be given (as root) before checking
that everything works. Installation is extremely
simple. Do: # make
install. Check afterwards that the
script /sbin/hotplug exists.
This is the last installation. Study the README file and
follow the instructions necessary to be able to run
make
USE_KLIBC=true. If you have
compiled the Linux-2.6.x kernel, this should not be too
difficult. A quick check would be to find out if
/sbin/udev and
/sbin/udevinfo exist. There are
other occurences as well, a very important one being
/etc/udev/udev.rules. If you have a
working setup for memory sticks (as described above) and
a memory stick plugged in you could try
ls /udev, you
should see the device (sda, sda1, ...). If it is there,
unplug the device and list again. It should be gone!
12.4.2. Naming memory sticks
With the udev utility in place, it
is possible to identify a memory stick on the basis of
some built-in attribute. One that works, is the
vendor identity. To find this for an
attached device, do systool
-vb scsi | grep vendor. This
should give a list of attached SCSI devices (remember
that your memory stick poses as a SCSI device Section 6.2). Let us suppose that you have two
memory sticks plugged in at the same time and found (as I
did) two vendor Id's, namely "UFD" and "STORAGE". Then
add to the file /etc/udev/udev.rules
the following lines (at the top if you like):
## Flash Memory 1
BUS="scsi", SYSFS_vendor="UFD*", NAME="namib%n"
## Flash Memory 2
BUS="scsi", SYSFS_vendor="STORAGE*", NAME="kalahari%n"
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The vendor-identities may have trailing blank spaces, and
therefore the wildcard asterisks have a purpose. Do not
ignore them. Remove and replace the memory sticks, then
do ls
/udev. Instead of the impersonal
sda, sda1,
etc. there should now be kalahari,
kalahari1,
namib and
namib1. The devices have been named
according to the "vendor" information in them. Thus we
can identify the device, no matter where it was
mapped. All that remains to be done is to creat
appropriate mount points like
/mnt/namib and
kalahari and make entries like
/udev/namib1 /mnt/namib vfat,ext2 user,noauto,rw 0 0
/udev/kalahari1 /mnt/kalahari vfat,ext2 user,noauto,rw 0 0
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in /etc/fstab to enable mounting
from other places.
This is great fun ... and remember, there are other
deserts on the planet.
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