NetBSD/sbin/restore/restore.8

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.\"     @(#)restore.8	8.4 (Berkeley) 5/1/95
.\"
.Dd July 15, 2018
.Dt RESTORE 8
.Os
.Sh NAME
.Nm restore ,
.Nm rrestore
.Nd "restore files or file systems from backups made with dump"
.Sh SYNOPSIS
.Nm
.Fl i
.Op Fl cdhmuvyN
.Op Fl b Ar bsize
.Op Fl D Ar algorithm
.Op Fl f Ar file
.Op Fl M Ar mfile
.Op Fl s Ar fileno
.Nm
.Fl R
.Op Fl cduvyN
.Op Fl b Ar bsize
.Op Fl D Ar algorithm
.Op Fl f Ar file
.Op Fl M Ar mfile
.Op Fl s Ar fileno
.Nm
.Fl r
.Op Fl cduvyN
.Op Fl b Ar bsize
.Op Fl D Ar algorithm
.Op Fl f Ar file
.Op Fl M Ar mfile
.Op Fl s Ar fileno
.Nm
.Fl t
.Op Fl cdhuvy
.Op Fl b Ar bsize
.Op Fl f Ar file
.Op Fl s Ar fileno
.Op Ar
.Nm
.Fl x
.Op Fl cdhmuvyN
.Op Fl b Ar bsize
.Op Fl D Ar algorithm
.Op Fl f Ar file
.Op Fl M Ar mfile
.Op Fl s Ar fileno
.Op Ar
.Pp
.in -\n[indent-synopsis]u
(The
.Bx 4.3
option syntax is implemented for backward compatibility, but
is not documented here.)
.Sh DESCRIPTION
The
.Nm
command performs the inverse function of
.Xr dump 8 .
A full backup of a file system may be restored and
subsequent incremental backups layered on top of it.
Single files and
directory subtrees may be restored from full or partial
backups.
.Nm
works across a network;
to do this see the
.Fl f
flag described below.
Other arguments to the command are file or directory
names specifying the files that are to be restored.
Unless the
.Fl h
flag is specified (see below),
the appearance of a directory name refers to
the files and (recursively) subdirectories of that directory.
.Pp
If any file arguments are given with the
.Fl x
flag,
or specified in the command shell with the
.Fl i
flag,
the permissions of the root directory
.Em will not
be applied to the current directory,
unless one of those file arguments explicitly represents the root inode
.Po e.g.:
a literal
.Sq \&.
.Pc .
This is a change from the traditional behaviour,
which used to be to always prompt the user.
.Pp
Exactly one of the following flags is required:
.Bl -tag -width Ds
.It Fl i
This mode allows interactive restoration of files from a dump.
After reading in the directory information from the dump,
.Nm
provides a shell like interface that allows the user to move
around the directory tree selecting files to be extracted.
The available commands are given below;
for those commands that require an argument,
the default is the current directory.
.Bl -tag -width Fl
.It Ic add Op Ar arg
The current directory or specified argument is added to the list of
files to be extracted.
If a directory is specified, then it and all its descendants are
added to the extraction list
(unless the
.Fl h
flag is specified on the command line).
Files that are on the extraction list are prepended with a
.Dq *
when they are listed by
.Ic ls .
.It Ic \&cd Ar arg
Change the current working directory to the specified argument.
.It Ic delete Op Ar arg
The current directory or specified argument is deleted from the list of
files to be extracted.
If a directory is specified, then it and all its descendants are
deleted from the extraction list
(unless the
.Fl h
flag is specified on the command line).
The most expedient way to extract most of the files from a directory
is to add the directory to the extraction list and then delete
those files that are not needed.
.It Ic extract
All the files that are on the extraction list are extracted
from the dump.
.Nm
will ask which volume the user wishes to mount.
The fastest way to extract a few files is to
start with the last volume, and work towards the first volume.
.It Ic help , \&?
List a summary of the available commands.
.It Ic \&ls Op Ar arg
List the current or specified directory.
Entries that are directories are appended with a
.Dq / .
Entries that have been marked for extraction are prepended with a
.Dq * .
If the verbose
flag is set the inode number of each entry is also listed.
.It Ic pwd
Print the full pathname of the current working directory.
.It Ic quit , Ic xit
Restore immediately exits,
even if the extraction list is not empty.
.It Ic setmodes
All the directories that have been added to the extraction list
have their owner, modes, and times set;
nothing is extracted from the dump.
This is useful for cleaning up after a restore has been prematurely aborted.
.It Ic verbose
The sense of the
.Fl v
flag is toggled.
When set, the verbose flag causes the
.Ic ls
command to list the inode numbers of all entries.
It also causes
.Nm
to print out information about each file as it is extracted.
.It Ic what
List dump header information.
.It Ic Debug
Enable debugging.
.El
.It Fl R
.Nm
requests a particular tape of a multi volume set on which to restart
a full restore
(see the
.Fl r
flag below).
This is useful if the restore has been interrupted.
.It Fl r
Restore (rebuild a file system).
The target file system should be made pristine with
.Xr newfs 8 ,
mounted and the user
.Xr cd 1 Ns 'd
into the pristine file system
before starting the restoration of the initial level 0 backup.
If the level 0 restores successfully, the
.Fl r
flag may be used to restore
any necessary incremental backups on top of the level 0.
The
.Fl r
flag precludes an interactive file extraction and can be
detrimental to one's health if not used carefully (not to mention
the disk).
An example:
.Bd -literal -offset indent
newfs /dev/rsd0g
mount /dev/sd0g /mnt
cd /mnt

restore rf /dev/rst0
.Ed
.Pp
Note that
.Nm
leaves a file
.Pa restoresymtable
in the root directory to pass information between incremental
restore passes.
This file should be removed when the last incremental has been
restored.
.Pp
.Nm ,
in conjunction with
.Xr newfs 8
and
.Xr dump 8 ,
may be used to modify file system parameters
such as size or block size.
.It Fl t
The names of the specified files are listed if they occur
on the backup.
If no file argument is given,
then the root directory is listed,
which results in the entire content of the
backup being listed,
unless the
.Fl h
flag has been specified.
Note that the
.Fl t
flag replaces the function of the old
.Ic dumpdir
program.
.ne 1i
.It Fl x
The named files are read from the given media.
If a named file matches a directory whose contents
are on the backup
and the
.Fl h
flag is not specified,
the directory is recursively extracted.
The owner, modification time,
and mode are restored (if possible).
If no file argument is given,
then the root directory is extracted,
which results in the entire content of the
backup being extracted,
unless the
.Fl h
flag has been specified.
.El
.Pp
The following additional options may be specified:
.Bl -tag -width Ds
.It Fl b Ar bsize
The number of kilobytes per dump record.
If the
.Fl b
option is not specified,
.Nm
tries to determine the block size dynamically.
.It Fl c
Normally,
.Nm
will try to determine dynamically whether the dump was made from an
old (pre-4.4) or new format file system.
The
.Fl c
flag disables this check, and only allows reading a dump in the old
format.
.It Fl D Ar algorithm
Computes the digest of each regular files using the
.Ar algorithm
and output to standard output.
The
.Ar algorithm
is one of
.Ar md5 ,
.Ar rmd160 ,
or
.Ar sha1 .
This option doesn't imply
.Fl N .
.It Fl d
Enable debugging.
.It Fl f Ar file
Read the backup from
.Ar file ;
.Ar file
may be a special device file
like
.Pa /dev/rst0
(a tape drive),
.Pa /dev/rsd1c
(a disk drive),
an ordinary file,
or
.Ql Fl
(the standard input).
If the name of the file is of the form
.Dq host:file ,
or
.Dq user@host:file ,
.Nm
reads from the named file on the remote host using
.Xr rmt 8 .
If the name of the file is
.Ql Fl ,
.Nm
reads from standard input.
Thus,
.Xr dump 8
and
.Nm
can be used in a pipeline to dump and restore a file system
with the command
.Bd -literal -offset indent
dump 0f - /usr | (cd /mnt; restore xf -)
.Ed
.It Fl h
Extract the actual directory,
rather than the files that it references.
This prevents hierarchical restoration of complete subtrees
from the dump.
.It Fl M Ar mfile
Do not set the file flags on restore.
Instead, append an
.Xr mtree 8
specification to
.Ar mfile ,
which can be used to restore file flags with a command such as
.Bd -literal -offset indent
sort mfile | mtree -e -i -u
.Ed
.It Fl m
Extract by inode numbers rather than by file name.
This is useful if only a few files are being extracted,
and one wants to avoid regenerating the complete pathname
to the file.
.It Fl N
Do not perform actual writing to disk.
.It Fl s Ar fileno
Read from the specified
.Ar fileno
on a multi-file tape.
File numbering starts at 1.
.It Fl u
The
.Fl u
(unlink)
flag removes files before extracting them.
This is useful when an executable file is in use.
Ignored if
.Fl t
or
.Fl N
flag is given.
.It Fl v
Normally
.Nm
does its work silently.
The
.Fl v
(verbose)
flag causes it to type the name of each file it treats
preceded by its file type.
.It Fl y
Do not ask the user whether to abort the restore in the event of an error.
Always try to skip over the bad block(s) and continue.
.El
.Pp
The historic alternate name
.Nm rrestore
was once required when restoring from a remote host.
This functionality is now built into
.Nm
itself.
.Sh ENVIRONMENT
If the following environment variable exists it will be used by
.Nm :
.Bl -tag -width "TMPDIR" -compact
.It TMPDIR
The directory given in TMPDIR will be used
instead of
.Pa /tmp
to store temporary files.
Refer to
.Xr environ 7
for more information.
.El
.Sh FILES
.Bl -tag -width "./restoresymtable" -compact
.It Pa /dev/nrst0
default tape unit to use.
Taken from
.Dv _PATH_DEFTAPE
in
.Pa /usr/include/paths.h .
.It Pa /dev/rst*
raw SCSI tape interface
.It Pa /tmp/rstdir*
file containing directories on the tape.
.It Pa /tmp/rstmode*
owner, mode, and time stamps for directories.
.It Pa \&./restoresymtable
information passed between incremental restores.
.El
.Sh DIAGNOSTICS
Complains if it gets a read error.
If
.Fl y
has been specified, or the user responds
.Ql y ,
.Nm
will attempt to continue the restore.
.Pp
If a backup was made using more than one tape volume,
.Nm
will notify the user when it is time to mount the next volume.
If the
.Fl x
or
.Fl i
flag has been specified,
.Nm
will also ask which volume the user wishes to mount.
The fastest way to extract a few files is to
start with the last volume, and work towards the first volume.
.Pp
There are numerous consistency checks that can be listed by
.Nm .
Most checks are self-explanatory or can
.Dq never happen .
Common errors are given below.
.Pp
.Bl -tag -width Ds -compact
.It Converting to new file system format.
A dump tape created from the old file system has been loaded.
It is automatically converted to the new file system format.
.Pp
.It <filename>: not found on tape
The specified file name was listed in the tape directory,
but was not found on the tape.
This is caused by tape read errors while looking for the file,
and from using a dump tape created on an active file system.
.Pp
.It expected next file <inumber>, got <inumber>
A file that was not listed in the directory showed up.
This can occur when using a dump created on an active file system.
.Pp
.It Incremental dump too low
When doing incremental restore,
a dump that was written before the previous incremental dump,
or that has too low an incremental level has been loaded.
.Pp
.It Incremental dump too high
When doing incremental restore,
a dump that does not begin its coverage where the previous incremental
dump left off,
or that has too high an incremental level has been loaded.
.Pp
.It Tape read error while restoring <filename>
.It Tape read error while skipping over inode <inumber>
.It Tape read error while trying to resynchronize
A tape (or other media) read error has occurred.
If a file name is specified,
then its contents are probably partially wrong.
If an inode is being skipped or the tape is trying to resynchronize,
then no extracted files have been corrupted,
though files may not be found on the tape.
.Pp
.It resync restore, skipped <num> blocks
After a dump read error,
.Nm
may have to resynchronize itself.
This message lists the number of blocks that were skipped over.
.El
.Sh SEE ALSO
.Xr rcmd 1 ,
.Xr rcmd 3 ,
.Xr environ 7 ,
.Xr dump 8 ,
.Xr mount 8 ,
.Xr newfs 8 ,
.Xr rmt 8
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .
.Sh BUGS
.Nm
can get confused when doing incremental restores from
dumps that were made on active file systems.
.Pp
A level zero dump must be done after a full restore.
Because
.Nm
runs in user mode,
it has no control over inode allocation;
thus a full dump must be done to get a new set of directories
reflecting the new inode numbering,
even though the content of the files is unchanged.
.Pp
The temporary files
.Pa /tmp/rstdir*
and
.Pa /tmp/rstmode*
are generated with a unique name based on the date of the dump
and the process ID (see
.Xr mktemp 3 ) ,
except for when
.Fl r
or
.Fl R
is used.
Because
.Fl R
allows you to restart a
.Fl r
operation that may have been interrupted, the temporary files should
be the same across different processes.
In all other cases, the files are unique because it is possible to
have two different dumps started at the same time, and separate
operations shouldn't conflict with each other.