Added -o flag to restore.

[dump.git] / rmt / rmt.8.in

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.\"     $Id: rmt.8.in,v 1.8 2002/04/15 11:57:29 stelian Exp $
.\"
.Dd __DATE__
.Dt RMT 8
.Os "rmt __VERSION__"
.Sh NAME
.Nm rmt
.Nd remote magtape protocol module
.Sh SYNOPSIS
.Nm rmt
.Sh DESCRIPTION
.Nm rmt
is a program used by the remote 
.Nm dump,
.Nm restore 
or
.Nm tar
programs in manipulating a magnetic tape drive through an interprocess
communication connection.
.Nm rmt
is normally started up with an
.Xr rexec 3
or
.Xr rcmd 3
call.
.Pp
The 
.Nm
program accepts requests specific to the manipulation of magnetic tapes, 
performs the commands, then responds with a status indication.  
All responses are in
.Tn ASCII
and in one of the following two forms.
.Pp
Successful commands have responses of:
.Bd -filled -offset indent
.Sm off
.Sy A Ar number No \en
.Sm on
.Ed
.Pp
where
.Ar number
is an
.Tn ASCII
representation of a decimal number.
.Pp
Unsuccessful commands are responded to with:
.Bd -filled -offset indent
.Sm off
.Xo Sy E Ar error-number
.No \en Ar error-message
.No \en
.Xc
.Sm on
.Ed
.Pp
where
.Ar error-number
is one of the possible error numbers described in
.Xr intro 2
and
.Ar error-message
is the corresponding error string as printed from a call to
.Xr perror 3 .
.Pp
The protocol is comprised of the
following commands, which are sent as indicated - no spaces are supplied
between the command and its arguments, or between its arguments, and
.Ql \en
indicates that a newline should be supplied:
.Bl -tag -width Ds
.Sm off
.It Xo Sy \&O Ar device
.No \en Ar mode No \en
.Xc
.Sm on
Open the specified 
.Ar device
using the indicated
.Ar mode .
.Ar Device
is a full pathname and
.Ar mode
is an
.Tn ASCII
representation of a decimal number suitable for passing to
.Xr open 2 .
If a device had already been opened, it is closed before a 
new open is performed.
.Sm off
.It Xo Sy C Ar device No \en
.Xc
.Sm on
Close the currently open device.  The
.Ar device
specified is ignored.
.Sm off
.It Xo Sy L
.Ar whence No \en
.Ar offset No \en
.Xc
.Sm on
Perform an
.Xr lseek 2
operation using the specified parameters.
The response value is that returned from the
.Xr lseek
call.
.Sm off
.It Sy W Ar count No \en
.Sm on
Write data onto the open device.
.Nm rmt
reads
.Ar count
bytes from the connection, aborting if a premature end-of-file is encountered.
The response value is that returned from the
.Xr write 2
call.
.Sm off
.It Sy R Ar count No \en
.Sm on
Read
.Ar count
bytes of data from the open device.
If
.Ar count
exceeds the size of the data buffer (10 kilobytes), it is
truncated to the data buffer size.
.Nm rmt
then performs the requested 
.Xr read 2
and responds with 
.Sm off
.Sy A Ar count-read No \en
.Sm on
if the read was successful; otherwise an error in the standard format 
is returned.  If the read was successful, the data read is then sent.
.Sm off
.It Xo Sy I Ar operation
.No \en Ar count No \en
.Xc
.Sm on
Perform a
.Dv MTIOCOP
.Xr ioctl 2
command using the specified parameters.  The parameters are interpreted as the
.Tn ASCII
representations of the decimal values to place in the 
.Ar mt_op
and
.Ar mt_count
fields of the structure used in the
.Xr ioctl
call.  The return value is the
.Ar count
parameter when the operation is successful.
.Pp
By issuing the
.Ql I-1\en0\en
command, a client will specify that he is using the VERSION 1 protocol.
.Pp
For a VERSION 0 client, the
.Ar operation
parameter is the platform 
.Ar mt_op
value (could be different if the client and the
.Nm
server are on two different platforms). For a VERSION 1 client,
the 
.Ar operation
parameter is standardized as below:
.Bl -tag -width Fl
.It Ic 0
Issue a MTWEOF command (write
.Ar count
end-of-file records).
.It Ic 1
Issue a MTFSF command (forward space over
.Ar count
file marks).
.It Ic 2
Issue a MTBSF command (backward space over
.Ar count
file marks).
.It Ic 3
Issue a MTFSR command (forward space
.Ar count
inter-record gaps).
.It Ic 4
Issue a MTBSR command (backward space
.Ar count
inter-record gaps).
.It Ic 5
Issue a MTREW command (rewind).
.It Ic 6
Issue a MTOFFL command (rewind and put the drive offline).
.It Ic 7
Issue a MTNOP command (no operation, set status only).
.El
.Sm off
.It Xo Sy i Ar operation
.No \en Ar count No \en
.Xc
.Sm on
Perform an extended
.Dv MTIOCOP
.Xr ioctl 2
command using the specified parameters.
The parameters are interpreted as the
.Tn ASCII
representations of the decimal values to place in the 
.Ar mt_op
and
.Ar mt_count
fields of the structure used in the
.Xr ioctl
call.  The return value is the
.Ar count
parameter when the operation is successful.
The possible operations are:
.Bl -tag -width Fl
.It Ic 0
Issue a MTCACHE command (switch cache on).
.It Ic 1
Issue a MTNOCACHE command (switch cache off).
.It Ic 2
Issue a MTRETEN command (retension the tape).
.It Ic 3
Issue a MTERASE command (erase the entire tape).
.It Ic 4
Issue a MTEOM command (position to end of media).
.It Ic 5
Issue a MTNBSF command (backward space count files to BOF).
.El
.ne 1i
.Sm off
.It Sy S
.Sm on
Return the status of the open device, as
obtained with a
.Dv MTIOCGET
.Xr ioctl
call.  If the operation was successful,
an ``ack'' is sent with the size of the
status buffer, then the status buffer is
sent (in binary, which is non-portable between different platforms).
.Sm off
.It Xo Sy s Ar sub-command
.Xc
.Sm on
This is a replacement for the previous S command, portable across different
platforms. If the open device is a magnetic tape, return members of the 
magnetic tape status structure, as obtained with a
.Dv MTIOCGET 
ioctl call. If the open device is not a magnetic tape, an error is returned.
If the 
.Dv MTIOCGET
operation was successful, the numerical value of the structure member is 
returned in decimal. The following sub commands are supported:
.Bl -tag -width Fl
.It Ic T
return the content of the structure member
.Ar mt_type
which contains the type of the magnetic tape device.
.It Ic D
return the content of the structure member
.Ar mt_dsreg
which contains the "drive status register".
.It Ic E
return the content of the structure member
.Ar mt_erreg
which contains the "error register". This structure member must be retrieved
first because it is cleared after each
.Dv MTIOCGET
ioctl call.
.It Ic R
return the content of the structure member
.Ar mt_resid
which contains the residual count of the last I/O.
.It Ic F
return the content of the structure member
.Ar mt_fileno
which contains the file number of the current tape position.
.It Ic B
return the content of the structure member
.Ar mt_blkno
which contains the block number of the current tape position.
.It Ic f
return the content of the structure member
.Ar mt_flags
which contains MTF_ flags from the driver.
.It Ic b
return the content of the structure member
.Ar mt_bf
which contains the optimum blocking factor.
.El
.El
.Sm on
.Pp
Any other command causes 
.Nm
to exit.
.Sh DIAGNOSTICS
All responses are of the form described above.
.Sh SEE ALSO
.Xr rcmd 3 ,
.Xr rexec 3 ,
.Xr /usr/include/sys/mtio.h ,
.Xr rdump 8 ,
.Xr rrestore 8
.Sh BUGS
People should be discouraged from using this for a remote
file access protocol.
.Sh AUTHOR
The
.Nm dump/restore
backup suit was ported to Linux's Second Extended File System
by Remy Card <card@Linux.EU.Org>. He maintained the initial versions
of dump (up and including 0.4b4, released in january 1997).
.Pp
Starting with 0.4b5, the new maintainer is Stelian Pop
.br
<stelian@popies.net>.
.Sh AVAILABILITY
The
.Nm dump/restore
backup suit is available from 
.br
http://dump.sourceforge.net
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .