doc/sg_persist.8

.TH SG_PERSIST "8" "October 2007" "sg3_utils\-1.25" SG3_UTILS
.SH NAME
sg_persist \- sends a SCSI PERSISTENT RESERVE (IN or OUT) command
to manipulate registrations and reservations
.SH SYNOPSIS
.B sg_persist
[\fIOPTIONS\fR] \fIDEVICE\fR
.PP
.B sg_persist
[\fIOPTIONS\fR] \fI\-\-device=DEVICE\fR
.PP
.B sg_persist
\fI\-\-help\fR | \fI\-\-version\fR
.SH DESCRIPTION
.\" Add any additional description here
.PP
This utility allows Persistent reservations and registrations to be
queried and changed. Persistent reservations and registrations are
queried by sub\-commands (called "service actions" in SPC\-4) of the
SCSI PERSISTENT RESERVE IN (PRIN) command. Persistent reservations and
registrations are changed by sub\-commands of the SCSI PERSISTENT RESERVE
OUT (PROUT) command.
.PP
There is a two stage process to obtain a persistent reservation. First an
application (an I_T nexus in standard's jargon) must register a reservation
key. If that is accepted (and it should be unless some other I_T nexus has
registered that key) then the application can try and reserve the device.
The reserve operation must specify the reservation key and a "type" (see
the \fI\-\-prout\-type=TYPE\fR option).
.PP
It is relatively safe to query the state of Persistent reservations and
registrations. With no options this utility defaults to the READ KEYS
sub\-command of the PRIN command. Other PRIN sub\-commands are
READ RESERVATION, REPORT CAPABILITIES and READ FULL STATUS.
.PP
Before trying to change Persistent reservations and registrations users
should be aware of what they are doing. The relevant sections of the
SCSI Primary Commands document (i.e. SPC\-4 whose most recent draft is
revision 9 dated 17th February 2007) are sections 5.6 (titled "Reservation"),
6.13 (for the PRIN command) and 6.14 (for the PROUT command). To safeguard
against accidental use, the \fI\-\-out\fR option must be given when a
PROUT sub\-command (e.g.  \fI\-\-register\fR) is used.
.PP
The older SCSI RESERVE and RELEASE commands (both 6 and 10 byte variants)
are not supported by this utility. In SPC\-3, RESERVE and RELEASE are 
deprecated, replaced by Persistent Reservations. RESERVE and RELEASE
have been removed from SPC\-4 and Annex B is provided showing how to
convert to persistent reservation commands. See a utility
called 'scsires' for support of the SCSI RESERVE and RELEASE commands.
.PP
The \fIDEVICE\fR is required by all variants of this utility apart
from \fI\-\-help\fR. The \fIDEVICE\fR can be given either as an
argument (typically but not necessarily the last one) or via
the \fI\-\-device=DEVICE\fR option.
.PP
SPC\-4 does not use the term "sub\-command". It uses the term "service action"
for this and for part of a field's name in the parameter block associated
with the PROUT command (i.e. "service action reservation key"). To lessen
the potential confusion the term "sub\-command" has been introduced. 
.SH OPTIONS
Arguments to long options are mandatory for short options as well.
The following options are sorted in alphabetical order, based on their
long option name.
.TP
\fB\-C\fR, \fB\-\-clear\fR
Clear is a sub\-command of the PROUT command. It releases the
persistent reservation (if any) and clears all registrations from the
device. It is required to supply a reservation key that is registered
for this I_T_L nexus (identified by \fI\-\-param\-rk=RK\fR).
.TP
\fB\-d\fR, \fB\-\-device\fR=\fIDEVICE\fR
\fIDEVICE\fR to send SCSI commands to. The \fIDEVICE\fR can either be
provided via this option or via a freestanding argument. For example,
these two: 'sg_persist \-\-device=/dev/sg2' and 'sg_persist /dev/sg2'
are equivalent.
.TP
\fB\-h\fR, \fB\-\-help\fR
output a usage message.
.TP
\fB\-H\fR, \fB\-\-hex\fR
the response to a valid PRIN sub\-command will be output in hexadecimal.
By default (i.e. without this option) if the PRIN sub\-command is recognised
then the response will be decoded as per SPC\-4.
.TP
\fB\-i\fR, \fB\-\-in\fR
specify that a SCSI PERSISTENT RESERVE IN command is required. This
is the default.
.TP
\fB\-n\fR, \fB\-\-no\-inquiry\fR
the default action is to do a standard SCSI INQUIRY command and output
make, product and revision strings plus the peripheral device type
prior to executing a PRIN or PROUT command. With this option the
INQUIRY command is skipped.
.TP
\fB\-o\fR, \fB\-\-out\fR
specify that a SCSI PERSISTENT RESERVE OUT command is required.
.TP
\fB\-Y\fR, \fB\-\-param\-alltgpt\fR
set the 'all target ports' (ALL_TG_PT) flag in the parameter block of the
PROUT command. Only relevant for 'register' and 'register and ignore existing
key' sub\-commands.
.TP
\fB\-Z\fR, \fB\-\-param\-aptpl\fR
set the 'activate persist through power loss' (APTPL) flag in the parameter
block of the PROUT command. Relevant for 'register', 'register and ignore
existing key' and 'register and move' sub\-commands.
.TP
\fB\-K\fR, \fB\-\-param\-rk\fR=\fIRK\fR
specify the reservation key found in the parameter block of the PROUT
command. \fIRK\fR is assumed to be hex (up to 8 bytes long). Default value
is 0. This option is needed by most PROUT sub\-commands.
.TP
\fB\-S\fR, \fB\-\-param\-sark\fR=\fISARK\fR
specify the service action reservation key found in the parameter block
of the PROUT command. \fISARK\fR is assumed to be hex (up to 8 bytes long).
Default value is 0. This option is needed by some PROUT sub\-commands.
.TP
\fB\-P\fR, \fB\-\-preempt\fR
Preempt is a sub\-command of the PROUT command. Preempts the existing
persistent reservation (identified by \fI\-\-param\-sark=SARK\fR) with
the registration key that is registered for this I_T_L nexus (identified
by \fI\-\-param\-rk=RK\fR). The associated \fI\-\-prout\-type=TYPE\fR option
needs to match the type of the reservation.
.TP
\fB\-A\fR, \fB\-\-preempt\-abort\fR
Preempt and Abort is a sub\-command of the PROUT command. Preempts
the existing persistent reservation (identified by \fI\-\-param\-sark=SARK\fR)
with the registration key that is registered for this I_T_L nexus (identified
by \fI\-\-param\-rk=RK\fR). The associated \fI\-\-prout\-type=TYPE\fR option
needs to match the type of the reservation. ACA and other pending tasks are
aborted.
.TP
\fB\-T\fR, \fB\-\-prout\-type\fR=\fITYPE\fR
specify the PROUT command's 'type' argument. Required by 
the 'register\-move', 'reserve', 'release' and 'preempt (and abort)'
sub\-commands. Valid \fITYPE\fR values: 1\-> write exclusive, 3\->
exclusive access, 5\-> write exclusive \- registrants only, 6\-> 
exclusive access \- registrants only, 7\-> write exclusive \- all registrants,
8\-> exclusive access \- all registrants. Default value is 0 (which is
an invalid type). Each "persistent reservation type" is explained in more
detail in a subsection of that name in the read reservation section of
the PRIN command (section 6.13.3.4 of SPC\-4 revision 9). 
.TP
\fB\-s\fR, \fB\-\-read\-full\-status\fR
Read Full Status is a sub\-command of the PRIN command. For each registration
with the given SCSI device, it lists the reservation key and associated
information. TransportIDs, if supplied in the response, are decoded.
.TP
\fB\-k\fR, \fB\-\-read\-keys\fR
Read Keys is a sub\-command of the PRIN command. Lists all the reservation
keys registered (i.e. registrations) with the given SCSI device. This is
the default sub\-command for the SCSI PRIN command.
.TP
\fB\-r\fR, \fB\-\-read\-reservation\fR
Read Reservation is a sub\-command of the PRIN command. List information
about the current holder of the reservation on the \fIDEVICE\fR. If there
is no current reservation this will be noted. Information about the current
holder of the reservation includes its reservation key, scope and type.
.TP
\fB\-s\fR, \fB\-\-read\-status\fR
same as \fI\-\-read\-full\-status\fR.
.TP
\fB\-G\fR, \fB\-\-register\fR
Register is a sub\-command of the PROUT command. It has 3 different
actions depending on associated parameters. a) add a new registration 
with '\-\-param\-rk=0' and '\-\-param\-sark=<new_rk>'; b) Change an existing
registration with '\-\-param\-rk=<old_rk>'
and '\-\-param\-sark=<new_rk>'; or  c) Delete an existing registration
with '\-\-param\-rk=<old_rk>' and '\-\-param\-sark=0'.
.TP
\fB\-I\fR, \fB\-\-register\-ignore\fR
Register and Ignore Existing Key is a sub\-command of the PROUT command.
Similar to \fI\-\-register\fR except that when changing a reservation key
the old key is not specified. The '\-\-prout-sark=<new_rk>' option should
also be given.
.TP
\fB\-M\fR, \fB\-\-register\-move\fR
register (another initiator) and move (the reservation held by the current
initiator to that other initiator) is a sub\-command of the PROUT command.
It requires the transportID of the other initiator. [The standard uses the
term I_T nexus but the point to stress is that there are two initiators
(the one sending this command and another one) but only one logical unit.]
The \fI\-\-prout\-type=TYPE\fR and \fI\-\-param\-rk=RK\fR options need to
match that of the existing reservation while \fI\-\-param\-sark=SARK\fR
option specifies the reservation key of the new (i.e. destination)
registration.
.TP
\fB\-Q\fR, \fB\-\-relative\-target\-port\fR=\fIRTPI\fR
relative target port identifier that reservation is to be moved to by
PROUT 'register and move' sub\-command. \fIRTPI\fR is assumed to be hex
in the range 0 to ffff inclusive. Defaults to 0 .
.TP
\fB\-L\fR, \fB\-\-release\fR
Release is a sub\-command of the PROUT command. It releases the
current persistent reservation. The \fI\-\-prout\-type=TYPE\fR 
and \fI\-\-param\-rk=RK\fR options, matching the reservation, must also be
specified.
.TP
\fB\-c\fR, \fB\-\-report\-capabilities\fR
Report Capabilities is a sub\-command of the PRIN command. It lists
information about the aspects of persistent reservations that the
\fIDEVICE\fR supports.
.TP
\fB\-R\fR, \fB\-\-reserve\fR
Reserve is a sub\-command of the PROUT command. It creates a new
persistent reservation (if permitted). The \fI\-\-prout\-type=TYPE\fR
and \fI\-\-param\-rk=RK\fR options must also be specified.
.TP
\fB\-X\fR, \fB\-\-transport\-id\fR=\fIH,H...\fR
a transportID is required for the PROUT 'register and move' sub\-command
and is optional for the PROUT 'register' and 'register and ignore
existing key' sub\-commands. The latter two sub\-commands can take multiple
transportIDs in a list but only one is supported with this option
variant (use the following option variant that reads stdin if multiple
transportIDs are required). \fIH,H...\fR is a comma separated list of hex
bytes which represent the transportID. The list of hex numbers will be
padded out with zeros to 24 bytes which is the minimum length of a
transportID. A transportID longer than 24 bytes (e.g. for iSCSI) is
padded with zeros so its length is a multiple of 4.
.TP
\fB\-X\fR, \fB\-\-transport\-id=\-\fR
a transportID is required for the PROUT 'register and move' sub\-command
and is optional for the PROUT 'register' and 'register and ignore
existing key' sub\-commands. The latter two sub\-commands can take multiple
transportIDs in a list. The argument is '\-' which indicates
stdin should be read for the transportID(s). Empty lines are ignored.
Everything from and including a "#" on a line is ignored.
Leading spaces and tabs are ignored. All numbers
are assumed to be hexadecimal and can be separated by space, comma or
tab. There can be one transportID per line. TranportIDs will be padded
out with zeros to 24 bytes which is the minimum length of a
transportID. A transportID longer than 24 bytes (e.g. for iSCSI) is
padded with zeros so its length is a multiple of 4.
.TP
\fB\-U\fR, \fB\-\-unreg\fR
optional when the PROUT register and move sub\-command is invoked. If given
it will unregister the current initiator (I_T nexus) after the other initiator
has been registered and the reservation moved to it. When not given the
initiator (I_T nexus) that sent the PROUT command remains registered.
.TP
\fB\-v\fR, \fB\-\-verbose\fR
print out cdb of issued commands prior to execution. If used twice
prints out the parameter block associated with the PROUT command prior
to its execution as well. If used thrice decodes given transportID(s)
as well. To see the response to a PRIN command in low level form use
the \fI\-\-hex\fR option.
.TP
\fB\-V\fR, \fB\-\-version\fR
print out version string. Ignore all other parameters.
.TP
\fB\-?\fR
output usage message. Ignore all other parameters.
.SH NOTES
In the 2.4 series of Linux kernels the \fIDEVICE\fR must be
a SCSI generic (sg) device. In the 2.6 series any SCSI device 
name (e.g. /dev/sdc, /dev/st1m or /dev/sg3) can be specified. 
For example "sg_persist \-\-read\-keys /dev/sda"
will work in the 2.6 series kernels.
.PP
The only scope for PROUT commands supported in the current draft of 
SPC\-4 is "LU_SCOPE". Hence there seems to be no point in offering an
option to set scope to another value.
.PP
Most errors with the PROUT sub\-commands (e.g. missing or 
mismatched \fI\-\-prout\-type=TYPE\fR) will result in a RESERVATION
CONFLICT status. This can be a bit confusing when you know there is
only one (active) initiator: the "conflict" is with the SPC standard, not
another initiator.
.PP
TransportIDs are defined in SPC\-4 and their structures vary depending
on the underlying transport.
.SH EXAMPLES
.PP
Due to defaults the simplest example executes the 'read keys' sub\-command
of the PRIN command:
.PP
   sg_persist /dev/sda
.PP
This is the same as the following (long\-winded) command:
.PP
   sg_persist \-\-in \-\-read\-keys \-\-device=/dev/sda
.PP
To read the current reservation either the '\-\-read\-reservation' form or
the shorter '\-r' can be used:
.PP
   sg_persist \-r /dev/sda
.PP
To
.B register
the new reservation key 0x123abc the following could be used:
.PP
   sg_persist \-\-out \-\-register \-\-param\-sark=123abc /dev/sda
.PP
Given the above registration succeeds, to
.B reserve
the \fIDEVICE\fR (with type 'write exclusive') the following
could be used:
.PP
   sg_persist \-\-out \-\-reserve \-\-param\-rk=123abc
.br
              \-\-prout\-type=1 /dev/sda
.PP
To
.B release
the reservation the following can be given (note that
the \-\-param\-rk and \-\-prout\-type arguments must match those of the
reservation):
.PP
   sg_persist \-\-out \-\-release \-\-param\-rk=123abc
.br
              \-\-prout\-type=1 /dev/sda
.PP
Finally to
.B unregister
a reservation key (and not effect other
registrations which is what '\-\-clear' would do) the command
is a little surprising:
.PP
   sg_persist \-\-out \-\-register \-\-param\-rk=123abc /dev/sda
.PP
Now have a close look at the difference between the register and
unregister examples above.
.PP
An example file that is suitably formatted to pass transportIDs via
the '\-\-transport\-id=\-' option can be found in the examples sub\-directory
of the sg3_utils package. That file is called 'transport_ids.txt'.
.SH EXIT STATUS
The exit status of sg_persist is 0 when it is successful. Otherwise see
the sg3_utils(8) man page.
.SH AUTHOR
Written by Doug Gilbert
.SH "REPORTING BUGS"
Report bugs to <dgilbert at interlog dot com>.
.SH COPYRIGHT
Copyright \(co 2004\-2007 Douglas Gilbert
.br
This software is distributed under the GPL version 2. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
.SH "SEE ALSO"
.B scsires(internet), examples/sg_persist_tst.sh(sg3_utils tarball)