Section: Maintenance Commands (8)
Updated: $Date: 2003/02/14 21:53:55 $
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iscsid - establish iSCSI connections
[ -d ]
[ -n ]
establishes connections with iSCSI targets defined in
Once the Linux iSCSI driver is activated, a discovery process for
iSCSI storage devices will proceed as follows:
The iSCSI daemon requests available iSCSI targets from the
iSCSI target, and passes the information discovered to the
iSCSI kernel module.
The iSCSI kernel module establishes connections to the targets.
Linux queries targets for device information.
Linux creates a mapping from SCSI device nodes to iSCSI targets.
should be started after networking is configured and
stopped after all iSCSI devices have been unmounted.
Warning: Data corruption can occur if you do not unmount iSCSI devices
before disabling network interfaces!
Because Linux assigns SCSI device nodes dynamically whenever
a SCSI logical unit is detected, the mapping from device nodes
(e.g /dev/sda, /dev/sdb) to iSCSI targets and logical units may
Variations in process scheduling and network delay may result in
iSCSI targets being mapped to different SCSI device nodes every time
the driver is started. Because of this variability, configuring
applications or operating system utilities to use the standard
SCSI device nodes to access iSCSI devices may result in SCSI
commands being sent to the wrong target or logical unit.
To provide a more reliable namespace, the iSCSI driver will scan the
system to determine the mapping from SCSI device nodes to iSCSI
targets, and then create a tree of directories and symbolic links
under /dev/iscsi to make it easier to use a particular iSCSI
target's logical units.
The iSCSI driver automatically maintains a bindings file
/var/iscsi/bindings. This file contains persistent bindings
to ensure that the same iSCSI bus and target id number are
used for every iSCSI session to a particular iSCSI TargetName,
no matter how many times the driver is restarted.
This feature ensures that the SCSI numbers in the device symlinks
described above will always map to the same iSCSI target.
Note that because of the way Linux dynamically allocates SCSI device
nodes as SCSI devices are found, the driver does not and can not
ensure that any particular SCSI device node (e.g. /dev/sda) will
always map to the same iSCSI TargetName. The symlinks described
in the section on Device Names are intended to provide a persistent
device mapping for use by applications and fstab files, and should
be used instead of direct references to particular SCSI device nodes.
If the bindings file grows too large, lines for targets that no
longer exist may be manually removed by editing the file. Manual
editing should not normally be needed, since the driver can maintain
up to 65535 different bindings.
- -b bindingfile
Specify an alternative bindings file instead of
which is the default.
Turns on debug mode. Each occurence of
will increment the debug level by one. The default is zero (off).
- -f configfile
Specify an alternative configuration file instead of
which is the default.
- -l basedir
Specify the base directory under which to build a tree of directories
containing symlinks to SCSI device nodes, in a manner similar to the
Linux kernel option. Using these symlinks hides variations in the
mapping from SCSI device nodes to SCSI device id numbers.
- -m mode
Specify the directory permission mode (in octal) to use when creating
Print version and exit.
reacts to a set of signals. You may easily send a signal to
using the following:
kill -SIGNAL `cat /var/run/iscsid.pid`
The daemon and all of it's children will die.
sent to the main daemon process will restart all discovery processes
and reprobe LUNs on all targets.
and all of it's children will die after shutting down all of the
kernel's iSCSI sessions.
Wait for children.
The number of iSCSI targets and LUNs that can be used depends on the
number of SCSI device nodes supported by your kernel. Each iSCSI
target will be probed for up to 256 LUNs, until the Linux kernel's
limit of SCSI devices has been reached.
The iSCSI drivers, README files, and example configuration files are
available on the Linux-iSCSI homepage at:
target address and LUN configuration
persistent iSCSI InitiatorName
the process id of the running daemon
persistent bus and target id bindings for iSCSI TargetNames
information about iSCSI devices
a directory tree containing symlinks to iSCSI device nodes.
- DEVICE NAMES
- TARGET BINDINGS
- SEE ALSO
This document was created by
using the manual pages.
Time: 05:43:48 GMT, June 16, 2003