NAME
dar - disk archive
SYNOPSIS
dar [-c | -x | -l | -d | -t | -C | -+] [<path>/]<basename> [options]
dar -h
dar -V
DESCRIPTION
dar is a full featured backup tool, aimed for disks (floppy, CD-R(W),
DVD-R(W), zip, jazz, etc.)
dar can store a backup in several files (called "slices" in the
following) of a given size, eventually pausing or running a user
command/script before starting the next slice. This can allow for
example, the burning of the last generated slice on a CD-R, or changing
a floppy disk before continuing on the next one. Like its grand-
brother, the great "tar" command, dar may also use compression, at the
difference that compression is used inside the archive to be able to
have compressed slices of the defined size. But the most important
feature of dar is its ability to make differential backups. In other
words, backups that contain only new files or files that have changed
from a backup of reference. Moreover with differential backup, dar
also stores files that have been deleted since the backup of reference.
Thus, when restoring, first a full backup, then additional differential
backups, at each restoration you get the exact state of the filesystem
at the time of the backup. And of course, the reference backup may be a
full or a differential backup itself.
dar is the first backup program I know that can also remove files
during restoration! By the way, in this document, "archive" and
"backup" mean the same thing, and are used interchangeably.
Unlike the tar command, dar is not suited for directly writing to
tapes. So keep using tar for tape archives. Because, even when using
dar to write a slice on a tape, you will loose all the interest of
another feature of dar which is its ability to directly access any of
the archived files, even when compression is used. This way, and in
contrast to the tar command, dar is able to extract a given file much
faster from a backup and to also recover files that follow a data
corruption (loosing only the file in which data corruption has
occurred).
This, of course, has its limitations, in particular when data
corruption occurs in the vital part of the backup, i.e. the few first
bytes of each slice or the last part of the archive (the catalogue). In
case you need to store archives on a bad quality medium, you could
protect each slice with a Parchive recovery file. (see NOTES for more
information about Parchive, and how to transparently run Parchive from
dar)
Slices have a base name given on the command line, which is completed
by a dot, a number, a dot and the extension (dar) to form a filename.
On the command line you will never have to give the full file name of a
slice.
Let’s take an example:
considering the base name "joe", dar will make one
or several slices during backup process. The
filenames with of these slices are: joe.1.dar
joe.2.dar ... joe.10.dar ... etc. If you want to
extract, list, or use this backup as reference, you
will only have to use the base name, which is the
string "joe" in this example.
OPTIONS
COMMANDS:
Important note: Not all system actually support long options (Solaris,
FreeBSD, ...). For example --create will not be available on these
systems, and you will have to use -c instead. In the same way, not all
system do support optional arguments (FreeBSD without GNU getopt for
example), you then need to explicitly give the argument, for example in
place of "-z" you will need to give "-z 9", see "EXPLICIT OPTIONAL
ARGUMENTS" paragraph near the end of this document.
-c, --create [<path>/]<basename>
creates a backup with the name based on <basename>.
All the slices will be created in the directory
<path> if specified, else in the current directory.
If the destination filesystem is too small to
contain all the slices of the backup, the -p option
(pausing before starting new slices) might be of
interest. Else, in the case the filesystem is full,
dar will suspend the operation, asking for the user
to make free space, then continue its operation. To
make free space, the only thing you cannot do is to
touch the slice being written. If the filename is
"-" *and* no slice is asked for (no -s option) the
archive is produced on the standard output allowing
the user to send the resulting archive through a
pipe.
-x, --extract [<path>/]<basename>
extracts files from the given backup. Slices are
expected to be in the current directory or in the
directory given by <path>. It is also possible to
use symbolic links to gather slices that are not in
the same directory. Path may also point to a
removable device (floppy, CD, etc.), in this case,
to be able to mount/unmount the device, you must
not launch dar from that directory. In other words,
the current directory must not be that directory
(see tutorial for details).
-l, --list [<path>/]<basename>
lists the contents of the given backup. In general
dar will only require the first and the last slice
of the archive.
-t, --test [<path>/]<basename>
checks the backup integrity. Even without
compression, dar is able to detect at least one
error per file in the archive, thanks to a 16 bits
CRC recorded per file in the catalogue. If one
error has occurred in a file stored in the archive,
dar will report it in 100% of all cases. If two
errors have occurred, dar will see them in 93,8% of
the cases. If three errors occurred, dar will see
them in 100% of the cases. If four errors have
occurred, dar will see them in 90.6% of the cases,
etc.
-d, --diff [<path>/]<basename>
compares saved files in the backup with those in
the filesystem.
-C, --isolate [<path>/]<basename>
isolate a catalogue from its archive. The argument
is the basename of the file that will contain the
catalogue. The -A option is mandatory here to give
the name of the archive to extract the catalogue
from. Slicing is available (-s -S -p -b etc.). If
the filename is "-" *and* no slice is asked (no -s
option) the catalogue is produced on the standard
output, allowing the user to send the resulting
catalogue through a pipe. Note that there is no
difference in concept between a catalogue and an
archive. Thus you can do all operation on a
catalogue, in particular take it as reference for a
differential archive. A catalogue produced with -C
is just like a differential archive done right
after a full backup, (no data in it).
-+, --merge [<path>/]<basename>
create a subset archive from one or two existing
archives (the resulting archive name is the
argument to this command). The dar file selection
mechanism (see below) let the user decide which
files will be present in the resulting archive and
which one will be ignored. This option thus let the
user merge two archives in a single one (with a
filtering mechanism that accepts all files), as
well as this option let the user create a smaller
archive which data is taken from one or two
archives of reference. Note that at no time the
contents of the archives of reference is extracted
to real files and directories: this is an archive
to archive transfer, thus you may lack support for
Extended Attribute while you will be able to fully
manipulate files with their Extended Attributes
from one archive to the resulting one. If the
basename is "-" *and* no slice is asked (no -s
option), the archive is produced on standard output
allowing the user to send the resulting archive
through a pipe. The first mandatory archive of
reference if provided thanks to the -A option,
while the second "auxiliary" (and optional) archive
of reference is provided thanks to the -@ option.
Note that in the current status, the resulting
archive contains all files from the mandatory
archive of reference (that matched the file
selection mechanism) plus those file of the
auxiliary archive that are not already present in
the mandatory archive of reference. In other words,
no overwriting is possible, a more complex way to
solve conflicts will take place in a future
version. Last by default, archive data selected for
merging is uncompressed, and re-compressed. Thus
the merging operation can be used to change
compression algorithm of given archive as well as
change its encryption. But, for better performance
it is also possible thanks to the -ak option (see
below the -ak option for usage restrictions) to
merge files keeping them compressed, thus no
decompression/re-compression is performed at all,
which make the operation faster.
-h, --help displays help usage.
-V, --version displays version information.
GENERAL OPTIONS:
-v, --verbose[=s[kipped]]
verbose output. --verbose and --verbose=skipped are
independent. --verbose=skipped displays the files
being excluded by filters, while --verbose display
actions under process.
-q, --quiet Suppress the final statistics report. If no verbose
output is asked beside this option, nothing is
displayed if the operation succeeds.
-b, --beep makes the terminal ring when user action is
required (like for example the creation of a new
slice using the -p option)
-n, --no-overwrite do not allow overwriting of any file or slice.
-w, --no-warn Do not warn before overwriting file or slice. By
default (no -n and no -w) overwriting is allowed
but a warning is issued before proceeding. This
option may receive ’a’ as argument:
-wa, --no-warn=all This implies the -w option, and means that over
avoiding warning for file overwriting, DAR also
avoid signaling a file about to be removed when its
type is not the expected one. File are removed when
they have been recorded as deleted since the
archive of reference. At restoration of the
differential archive, if a file of the given name
exists, it is remove, but if the type does not
match the file that was present at the time of the
archive of reference (directory, plain file, fifo,
socket, char or block device, etc.), a warning is
normally issued to prevent the accidental removal
of data that was not saved in the backup of
reference. (See also -k option)
-R, --fs-root <path>
The path points to the directory tree containing
all the files that will be enrolled in the
operation (backup, restoration or comparison). By
default the current directory is used. All other
paths used in -P or -g options on the command line
are and must be relative to this path (or to
current directory if -R is not present). Note that
-R is useless for testing (-t option) isolation (-C
option) and merging (-+ option)
-X, --exclude <mask>
The mask is a string with wild cards (like * and ?)
which is applied to filenames which are not
directories. If a given file matches the mask, it
is excluded from the operation. By default (no -X
on the command line), no file is excluded from the
operation. -X may be present several times on the
command line, in that case a file will not be
considered for the given operation if it matches at
least one -X mask.
-I, --include <mask>
The mask is applied to filenames which are not
directories. If a given file matches the mask and
does not match any mask given with -X, the file is
selected for the operation. By default (no -I and
no -X on the command line), all files are included
for the operation. -I may be present several times
on the command line, in that case all file that
match one of the -I mask will be considered for the
given operation, if they do not also match one of
the -X mask.
-P, --prune <path> Do not consider file or directory sub-tree given by
the path. -P may be present several time on the
command line. The difference with -X is that the
mask is not applied only to the filename, but also
include the path. Moreover it applies also to
directories (-X does not). By default (no -P on the
command-line), no sub-tree or file is excluded from
the operation, and all the directory tree (as
indicated by -R option) is considered. Note that
<path> may contains wild-cards like * or ? see
glob(7) man page for more informations.
-g, --go-into <path>
Files or directory to only take in account, as
opposed to -P. -g may be present several time on
command-line. Same thing here, the difference with
-I is that the mask is applied to the path+filename
and also concerns directories. By default all files
under the -R directory are considered. Else, if one
or more -g option is given, just those are selected
(if they do not match any -P option). All paths
given this way must be relative to the -R
directory. This is equivalent as giving <path> out
of any option. Warning, -g option cannot receive
wild-cards, these would not be interpreted.
-[, --include-from-file <listing_file>
Files listed in the listing file are included for
the operation. No wild card expression is
interpreted in the listing file, the null character
is not allowed and the carriage return is used to
separate file names (one file name per line). Note
that this option applies to any files and directory
exactly as -g does, with an important difference
however: -g option only uses relative paths to the
root directory (the directory given with the -R
option), while -[ can use absolute path as well.
Another difference is when the argument is a
directory -g will include all the subdirectories
under that directory, while when the same entry is
found in a listing file given to -[ only that
directory will be included, no subdirectory or
subfile would be enrolled in the backup, with -[
you need to list the exact set of file you want to
backup. You can thus generate a listing file with
the ’find / -print > somefile’ command and give
’somefile’ as argument to -[ option. Note that
however, dar will not save files out of the -R
given root directory tree.
-], --exclude-from-file <listing_file>
Files listed in the listing file are excluded from
the operation. If a directory is listed in the file
all its contents is excluded (unless using ordered
method and another mask includes some of its
subfiles or subdirectories). This option is the
opposite of -[ and acts the same was as -P option
does (in particular it is compared to the whole
path+filename and applies to files and
directories). As for -[ option, -] listing file can
contain absolute paths, but wild cards are not
expanded, neither.
File selection in brief:
As seen above, -I -X -P, -g, -[ and -] options are used to select the
files to operate on. -I and -X only use the name of files and do not
apply to directories, while -P, -g -[ and -] use the filename *and* the
path, they *do* apply to directories.
since version 2.2.0 two modes of interpretation of these options exist.
The normal original method and the ordered method:
the normal method is the default:
A directory is elected for operation if no -P or -] option
excludes it. If at least one -g or -[ option is given one
command line, one -g option must cover it, else it is not
elected for operation. If a directory is not selected, no
recursion is done in it (the directory is pruned). For non
directories files, the same is true (P, -g, -[ and -] do
apply) and a second test must also be satisfied: no -X
option must exclude the filename, and if at least one -I
option is given, one must match the given filename (using
or not wild-cards).
the ordered method (when -am option is given on command-line):
The ordered method takes care of the order of presence
between -X and -I in one hand and of -P, -g, -[ and -] in
the other hand (note that it has also the same action
concerning EA selection when using -u and -U options, but
that’s no more file selection). In the ordered method the
last argument take precedence over all the previous ones,
let’s take an example:
-X "*.mp?" -I "*.mp3" -I "toto*"
Here dar will include all files except file of name
"*.mp?" (those ending with "mpX" where X is any
character), but it will however include those ending
with ".mp3". It will also include files which name
begin by "toto" whatever they end with. This way,
"toto.mp2" will be saved (while it matches "*.mp?" it
also begins by "toto") as well as "toto.txt" as well
as "joe.mp3" (while it matches "*.mp?" it also ends by
"mp3"). But will not be saved "joe.mp2" (because it
does not begin by "toto", nor ends by "mp3", and match
"*.mp?" mask). As we see the last option (-I or -X)
overcomes the previous one. -P, -g, -[ and -] act
together the same but as seen above they do not only
act on filename, but on the whole path+filename. Note
that (-g, -P, -[, -]) and (-X , -I) are independent
concerning their relative order. You can mix -X -I -g
-P -] -[ in any order, what will be important is the
relative positions of -X options compared to -I
options, and the relative positions of -g -[ -] and -P
options between them.
In logical terms, if <prev_mask> is the mask generated by all
previous mask on the command line, -I <mask> generates the new
following mask: <prev_mask> or <mask> . While -X <mask>
generates the new following mask: <prev_mask> and not <mask>.
This is recursive each time you add a -I or -X option. Things
work the same with -P, -g, -[ and -] options.
This ends the file selection explication let’s continue with other
options.
-u, --exclude-ea <mask>
Do not consider the Extended Attributes (EA) that
are matched by the given mask. By default, no EA
are excluded, if the support for EA has been
activated at compilation time. This option can be
used multiple times.
-U, --include-ea <mask>
Do only consider the EA that match the given mask.
By default, all EA are included if no -u or -U
option is present and if the support for EA has
been activated at compilation time. This option can
be used multiple times. See also the -am and -ae
options, they also apply to -U and -u options and
read below the Note concerning EA.
Note concerning Extended Attributes (EA)
Support for EA must be activated at compilation time (the
configure script tries to do so if your system has all the
required support for that). Thus you can get two binaries of dar
(of the same version), one supporting EA and another which does
not (dar -V to see whether EA support is activated). The
archives they produce are the same and can be read by each
other. The only difference is that the binary without EA support
is not able to save or restore EAs, but is still able to test
them and list their presence.
Since version 2.3.x the name of EA include the namespace for dar
be able to consider any type of EA (not only "system" and "user"
as previously). Thus the two previous options -u and -U have
changed and now take an argument which is a mask applied to EA
names written in the following form namespace.name where
"namespace" is for example "user". Note that the mask may or may
not include the dot (.) and match arbitrary part of the EA
namespace+name, just remind that masks will be applied to the
"namespace.name" global string.
the -am flag here also enables the ordered method, for EA
selection too. The ordered versus normal method have been
explained above in the file selection note, with some examples
using -X and -I. Here this is the same with -U and -u, (just
replace -X by -u and -I by -U and remember that the
corresponding mask will apply to Extended Attribute selection in
place of file selection).
Another point, independently of the -am option the -ae option
can be used at restoration time only. If set, when a file is
about to be overwritten, all EA will be first erased before
restoring those selected for restoration in the archive
(according to the -U and -u options given). If not set, the EA
of the existing file will be overwritten, those extra EA that
are not in the archive or are not selected for restoration in
regard to the -u and -U options will be preserved. If you have
not used any -u/-U option at backup time and want to restore
from a set of full/differential backups the EA exactly as they
were, you have to use -ae for dar removes the EA before
overwriting their set of EA as stored in the archive. Without
-ae option dar will simply add EA to existing ones, thus get a
different set of EA for a give file than those recorded at the
time of the backup.
Last point the -acase and -an options alters the case
sensitivity of the -U and -u masks that follow them on the
command-line/included files as they do for -I, -X, -P, -g, -[
and -] as well. Very last point ;-), by default during backup
dar set back the atime after having read each file (see -aa/-ac
options), this has as side effect to modify the ctime date of
each file. But ctime change is used by dar to detect EA changes.
In brief, the next time you backup a file that had to be read
(thus which contents changed), its EA will be saved even if they
had not changed. To avoid this slide effect, you can use the -ac
option.
This ends the Extended Attribute selection explication let’s continue
with other options.
-i, --input <path> is available when reading from pipe (basename is
"-" for -x, -l, -t, -d or for -A when -c, -C or -+
is used). When reading from pipe, standard input is
used, but with this option, the file <path>
(usually a named pipe) is used instead. This
option is to receive output from dar_slave program
(see doc/NOTES for examples of use).
-o, --output <path> is available when reading from pipe (basename is
"-" for -x, -l, -t, -d or for -A when -c, -C or -+
is used). When reading from pipe, standard output
is used to send request to dar_slave, but with this
option, the file <path> (usually a named pipe) is
used instead. When standard output is used, all
messages goes to standard error (not only
interactive messages). See doc/NOTES for examples
of use.
-O, --comparison-field[=<flag>]
When comparing with the archive of reference (-c
-A) during a differential backup, when extracting
(-x) or when comparing (-d) do only consider
certain fields. The available flags are:
ignore-owner all fields are considered except
ownership. This is useful when dar
is used by a non-privileged user. It
will not consider a file has changed
just because of a uid or gid
mismatch and at restoration dar will
not even try to set the file
ownership.
mtime only inode type and last
modification date is considered as
well as inode specific attributes
like file size for plain files.
Ownership is ignored, permission is
ignored. During comparison,
difference on ownership or
permission is ignored and at
restoration time dar will not try to
set the inode permission and
ownership.
inode-type Only the inode type is considered.
Ownership, permission and dates are
ignored. Inode specific attributes
are still considered (like file size
for plain files). Thus comparison
will ignore differences for
ownership, permission, and dates and
at restoration dar will not try to
set the ownership, permission and
dates.
When no flag is provided to this option, -O option acts as if the
"ignore-owner" flag was set, which is the behavior in older releases (<
2.3.0). Note also that for backward compatibility, --ignore-owner
option still exists and is now just an alias to the --comparison-
field=ignore-owner option. Of course if this option is not used, all
fields are used for comparison or restoration.
-H[num], --hour[=num]
if -H is used, two dates are considered equal if
they differ from a integer number of hours, and
that number is less than or equal to [num]. If not
specified num defaults to 1. This is used when
making a differential backup, to compare
last_modification date of inodes, and at
restoration time if the -r option (restore only
more recent files) is used. This is to workaround
some filesystems (like Samba filesystem) that seems
to change the dates of files after having gone from
or to daylight saving time (winter/summer time).
-E, --execute <string>
the string is a user command-line to be launched
between slices. For reading (thus using -t, -d, -l
or -x options), the command is executed before the
slice is read or even asked, for writing instead
(thus using -c, -C or -+ option), the command is
executed once the slice has been completed. Some
substitution string can be used in the string:
%% will be replaced by %
%p will be replaced by the slice path
%b will be replaced by the slice basename
%n will be replaced by the slice number (to
be read or just written). For reading,
dar often needs the last slice, but
initially it does not know its number. If
it cannot be found in the current
directory, the user command-line is then
called with %n equal to 0. This is a
convenient way to inform the user command
to provide the last slice. If after it is
still not present, dar asks the user (as
usually) with a message on the terminal.
Once the last slice is found, the user
command-line is called a second time,
with %n equal to the value of the last
slice number.
%e will be replaced by the slice extension
(always substituted by "dar")
%c will be replaced by the context. Actually
three possible values exist: "init",
"operation" and "last_slice". When
reading an archive for (testing,
extraction, diff, listing, or while
reading the archive of reference, see
below the -F option), the "init" context
takes place from the beginning up to the
time the catalogue is retrieved. On a
multiple slice archive this correspond to
the first slice request and to the last
slice requests. After, that point comes
the "operation" context. While creating
an archive, the context is always
"operation" except when the last slice
has been created, in which case the
context is set to "last_slice".
Several -E option can be given, given commands will then be called in
the order they appear on the command line, and included files.
-F, --execute-ref <string>
same as -E but is applied between slices of the
reference archive (-A option).
-K, --key [[<algo>]:]<string>
encrypt/decrypt the archive using the <algo> cipher
with the <string> as pass phrase. An encrypted
archive can only be read if the same pass phrase is
given. Available ciphers are "blowfish" (alias
"bf") for strong encryption and "scrambling" (alias
"scram") for a very weak encryption. By default if
no <algo> or no ’:’ is given, the blowfish cipher
is assumed. If your password contains a column ’:’
you need to specify the cipher to use (or at least
use the initial ’:’ which is equivalent to ’bf:’).
If the <string> is empty the pass phrase will be
asked at execution time. Thus, the smallest
argument that -K can receive is ’:’ which means
blowfish cipher with the pass phrase asked at
execution time.
With release 2.3.4 a better implementation of the blowfish algorithm
has been used within dar, while recent version can transparently read
older implementation (using ’bf’ cipher) you can create new archive
with this old weakened blowfish implementation using the
’blowfish_weak’ or ’bfw’ cipher. Note that this way of encryption is
strong but weakened by frequent IV collision (same Initial Vectors used
often). This feature is kept available for those using old openssl
library that do not provide all the header required to implement the
new blowfish implementation.
Note that giving the pass phrase as argument to -K (or -J see below)
may let other users learn pass phrase (thanks to the ps, or top program
for examples). It is thus wise to either use an empty pass which will
make dar ask the pass phrase at when needed, or use -K (or -J option)
from an Dar Command File (see -B option), assuming it has the
appropriated permission to avoid other users reading it.
-J, --key-ref [[<algo>]:]<string>
same as -K but the given key is used to decrypt the
archive of reference (given with -A option).
-#, --crypto-block <size>
to be able to randomly access data in an archive,
it is not encrypted globally but block by block.
You can define the encryption block size thanks to
this argument which default to 10240 bytes. Note
that syntax used for -s option is also available
here. Note also that crypto-block is stored as a 32
bits integer thus value larger than 4GB will cause
an error. Note last, that the block size given here
must be provided when reading this resulting
archive (through the -* or -# options). If it is
not the correct one, the archive will not be
possible to decrypt, it is thus safe to keep the
default value (and not use at all the -# option).
-*, --crypto-block-ref <size>
same as --crypto-block but for the archive of
reference (same default value).
-B, --batch <filename>
You can put in the file any option or argument as
used on command line, that will be parsed as if
they were in place of the "-B <filename>" option.
This way you can overcome the command line size
limitation. Commands in the file may be disposed on
several lines, and -B option can also be used
inside files, leading a file to include other
files. But an error occurs in case of loop (a file
includes itself) and DAR aborts immediately.
Comments are now allowed, and must start by a hash
‘#’ character on each line. Note that for a line to
be considered as comment the hash character must be
the first character of the line (space or tab can
still precede the hash). See Conditional Syntax
bellow for a more rich syntax in configuration
files.
-N, --noconf Do not try to read neither ~/.darrc nor /etc/darrc
configuration files. See files section bellow.
-e, --empty Do not perform any action (backup, restoration or
merging), displays all messages as if it was for
real ("dry run" action).
-aSI, --alter=SI[-unit[s]]
when using k M G T E Z Y prefixes to define a size,
use the SI meaning: multiple of 10^3 (a Mega is
1,000,000).
-abinary, --alter=binary[-unit[s]]
when using k M G T E Z Y prefixes to define a size,
use the historical computer science meaning:
multiple of 2^10 (a Mega is 1,048,576).
The --alter=SI and --alter=binary options can be used several times on
the command line. They affect all prefixes which follow, even those
found in files included by the -B option, up to the next --alter=binary
or --alter=SI occurrence. Note that if in a file included by the -B
option, an --alter=binary or --alter=SI is encountered, it affects all
the following prefixes, even those outside the included files. For
example, when running with the parameters "-B some.dcf -s 1K", 1K may
be equal to 1000 or 1024, depending on --alter=binary or --alter=SI
being present in the some.dcf file. By default (before any
--alter=SI/binary option is reached), binary interpretation of prefixes
is done, for compatibility with older versions.
-Q Do not display an initial warning on stderr when
not launched from a terminal (when launched from a
cronjob for example). This means that all questions
to the user will be answered with ’no’, which most
of the time will abort the program. Please note
that this option cannot be used in the
configuration file, it must be given on the command
line. Since version 2.2.2, giving this option also
forces the non-interactive mode, even if dar is
launched from a terminal. This makes it possible
for dar to run in the background. When you do, it’s
recommended to redirect stdout and/or sterr to
files.
-aa, --alter=atime when reading a filesystem, while doing a backup (-c
option) or comparing (-d option) by default dar
tries to be as much transparent as possible, and
set back the last access time (atime) of read files
and directories, as if they have not been read.
But, preserving atime of read files, make their
ctime to be changed (last inode change). There is
no possibility to preserve both atime and ctime. If
you want to overcome the default original behavior
of dar and want to keep ctime unchanged, the
--alter=atime is for you. Some security software
rely on the ctime to be preserved, some other
software rely on the atime to be preserved like
leafnode NNTP caching software.
-ac, --alter=ctime set back the date alteration to ctime (see
--alter=atime above), this is the default behavior.
The use of this switch is to override the -aa
option in dar configuration files or command-line
(see -B option). From -aa and -ac the one which is
last parsed from command-line or included files
takes the win.
-am, --alter=mask set the ordered mode for mask. This affects the way
-I and -X options are interpreted, as well as -g,
-P, -[ and -] options, -Z and -Y options and -U and
-u options. It can take any place on the command-
line and can be placed only once. See the file
selection in brief paragraph above for a detailed
explanation of this option.
-an, --alter=no-case
set the filters in case insensitive mode. This
concerns only masks specified after this option
(see also -acase option below). This changes the
behavior of -I, -X, -g, -P, -Z, -Y, -u and -U
options.
-acase, --alter=case
set back to case sensitive mode for filters. All
following masks are case sensitive, up to end of
parsing or up to the next -an option. This changes
the behavior of -I, -X, -g, -P, -Z, -Y, -u and -U
options.
-ar, --alter=regex set the filters to be interpreted as regular
expressions (man regex(7) ) instead of the default
glob expression (man glob(7) ) This modifies the
-I, -X, -g, -P, -Z, -Y, -u and -U options that
follows up to an eventual -ag option (see just
below). Note that for -P and -g options, the given
mask matches the relative path part of the files
path: Let’s take an example, assuming you have
provided /usr/local to the -R option, the mask
"^foo$" will replaced internally by
"^/usr/local/foo$" while the mask "foo$" will be
replaced internally by "^/usr/local/.*foo$".
-ag, --alter=glob This option returns to glob expressions mode (which
is the default) after an -ar option has been used,
this applies to any -I, -X, -g, -P, -Z, -Y, -u and
-U options that follow up to an eventual new -ar
option (see just above).
-j, --jog when virtual memory is exhausted, ask user to make
room before trying to continue. By default, when
memory is exhausted dar aborts. Note that on
several system, when memory is exhausted the kernel
is likely to kill the process that failed to obtain
virtual memory, thus on some systems, dar may not
be able to ask user for what to do when memory is
exhausted.
SAVING, ISOLATION AND MERGING OPTIONS (to use with -c, -C or -+)
-z[level], --gzip[=level]
compresses within slices using gzip algorithm (if
not specified, no compression is performed). The
compression level (an integer from 1 to 9) is
optional, and is 9 by default, which is max
compression/slow processing. At the opposite, 1
means less compression and faster processing.
-y[level], --bzip2[=level]
compresses using bzip2 algorithm. See -z above for
usage details.
-s, --slice <number>
Size of the slices in bytes. If the number is
appended by k (or K), M, G, T, P E, Z or Y the size
is in kilobytes, megabytes, gigabytes, terabytes,
petabytes, exabytes, zettabytes or yottabytes
respectively. Example: "20M" means 20 megabytes, by
default, it is the same as giving 20971520 as
argument (see also -aSI and -abinary options). If
-s is not present the backup will be written to a
single slice whatever the size of the backup may be
(there is probably some filesystem limitation, thus
you might expect problems for file size over 2
gigabytes, depending on your filesystem, but this
is not a limitation of dar).
-S, --first-slice <number>
-S gives the size of the first slice which may be
chosen independently of the size of following
slices. This option needs -s and by default, the
size of the first slice is the same as the one of
the following slices.
-p [<integer>], --pause[=<integer>]
pauses before writing to a new slice (this requires
-s). By default there is no pause, all slices are
written in the same directory, up to the end of the
backup or until the filesystem is full. In this
later case, the user is informed of the lack of
disk space and dar stops for user action. As soon
as some disk space is available, the user can
continue the backup. The optional integer that this
option can receive tells dar to only pause very ’n’
slice. Giving 3 for ’n’ will make dar pause only
after slices 3, 6, 9 and so on. If this integer is
not specified, the behavior is as if ’1’ was given
as argument which makes dar pause after each slice.
-A, --ref [<path>]/<basename>
specifies the archive to use as reference
(mandatory with -C). By default (default is only
possible with -c option) no archive is used and all
files are saved (in regards to -I -X -P and -g
options). All slices of the reference backup are
expected to be on the same directory given by
<path> or the current directory by default. Usually
only the first and the last slice are required to
extract the catalogue of reference. If necessary
the use of symbolic links is also possible here to
gather slices that do not reside in the same
directory. You can also point <path> to a floppy or
any other mounted directory, because dar will pause
and ask the user for required slices if they are
not present. The argument to -A may be of four
types:
- An existing archive basename, which will be
taken as reference
- a dash ("-") which implies the use of -o and -i
options, this allows the archive of reference to be
read from a pair of pipes with dar_slave at the
other ends. Dar_slave can be run through ssh on a
remote host for example.
- a plus sign ("+") which makes the reference be
the current directory status (not available with -+
option: merging). In other word, no file’s data
will be saved, just the current status of the
inodes will be recorded in the catalogue. This is
like an extracted catalogue form a full backup, it
can be taken for further reference without having
to make the full backup itself. This feature is
known as the "snapshot" backup.
- a <date>, if -af option has been placed before
-A on the command-line (or in a included file, see
-B option). For more about that feature see -af
option below.
-@, --aux-ref [<path>]/<basename>
specifies an auxiliary archive of reference. This
option is only available with -+ option (merging).
Over -A option which is mandatory with -+ option,
you may give a second archive of reference thanks
to the -% option. This allows one to merge two
archive in a single one. See also -$, -~ and -% for
other options concerning auxiliary archive of
reference.
-$, --aux-key [[<algo>]:]<string>
same as -J but for the auxiliary archive of
reference (-@ option).
-~, --aux-execute <string>
same as -F but for the auxiliary archive of
reference (-@ option).
-%, --aux-crypto-block <size>
same as -* but for the auxiliary archive of
reference (-@ option).
-D, --empty-dir When excluding directories either explicitly using
-P or -] options, or implicitly by giving a -g or
-[ options (a directory is excluded if it does not
match mask given with -g options or -[ options) dar
does not store anything about these. But with -D
option, dar stores them as empty directories. This
can be useful, if excluding a mount point (like
/proc or /dev/pts). At restoration time, dar will
then recreate these directories (if necessary).
This option has no meaning with -C and is ignored
in that case.
-Z, --exclude-compression <mask>
Filenames covered by this mask are not compressed.
It is only useful with -z or -y. By default, all
file are compressed (if compression is used). This
option can be used several times, in that case a
file that matches one of the -Z mask will not be
compressed.
-Y, --include-compression <mask>
Filenames covered by this mask (and not covered by
-Z) are the only to be compressed. It is only
available with -z no -y. By default all files are
compressed. This option can be used several times,
in that case all files that match one of the -Y
will be compressed, if they do not also match on of
the -Z masks. The ordered method here applies too
when activated (with -am option), it works exactly
the same as -I and -X options, but apply to file
compression, not file selection.
-m, --mincompr <number>
files which size is below this value will not be
compressed. If -m is not specified it is equivalent
to giving -m 100 as argument. If you want to
compress all file whatever their size is you thus
need to type -m 0 on the command line. The same
number extensions as those used with -s or -S are
available here, if you want to specify the size in
kilobyte, megabyte, gigabyte etc.
-ak, --alter=keep-compressed
During merging operation, keep files compressed,
this has several restrictions : -z, -y, -Z, -Y, -m
are ignored, if two archives have to be merged,
both must use the same compression algorithm or one
of them must not use compression at all (this last
restriction will probably disappear in a next
version). The advantage of this option is a greater
speed of execution (compression is usually CPU
intensive).
-af, --alter=fixed-date
Modify the -A option behavior, making it receiving
a <date> as argument in place of the
[<path>]/<basename> default argument. The <date> is
used to define which file to save (file which
modification is newer or equal to <date>) and which
to consider unchanged (those older than <date>).
This option has only a sense when creating an
archive (not when merging or isolating).
<date> must be a date in the following possible formats:
- a number of second since Jan 1st, 1970
- a date in the following form
[[[year/]month/]day-]hour:minute[:second]
Here are some examples of date:
91836383927108078
2005/11/19-19:38:48 Which is 38 past 7 PM and 48 seconds, the
19th of November 2005
20:20 Which is 8 PM of the current day
2-00:08 Which is 8 past noon, the second day of the current
month
2/2-14:59 Which is 1 to 3 PM, the 2nd of February in the current
year
--nodump do not save files which have the ’d’ flag set (see
chattr(1) lsattr(1) ext2 commands). This option may
not be available if the system dar has been
compiled on did not provide support for ext2 flags.
Note that this option does nothing with -+ option
(merging) as no filesystem is used for that
operation.
-G, --on-fly-isolate [<path>]/<basename>
When creating a backup (-c option) or merging two
backups (-+ option), -G option perform a catalogue
isolation of the resulting archive. This step is
done after the backup/merging has completed. The
on-fly isolation is compressed with bzip2 (using
compression level 9), and is a single sliced
archive without encryption. Due to command-line
exiguity, it is not possible to change compression
algo, slice size or encryption scheme for the on-
fly isolation. If you need a more complicated
isolation, either look for a GUI over libdar, or do
a normal (not on-fly) isolation (By the way it is
possible to isolate an already isolated catalogue,
this is equivalent to a copy, but you can add
encryption, change compression, change slicing,
etc.), you can also use dar_xform if you only want
to change slices size (this is faster as no
decompression/re-compression is done).
-M, --no-mount-points
stay in the same filesystem as the root directory
(see -R option), subdirectory that are mounting
points for other filesystems will not be saved or
saved empty if -D option is used (useless with -+
option)
-, , --cache-directory-tagging
don’t save contents of directories that use the
Cache Directory Tagging Standard. See
http://www.brynosaurus.com/cachedir/spec.html for
details. (this option is useless with -+ option)
RESTORATION OPTIONS (to use with -x)
-k, --no-deleted Do not delete files that have been deleted since
the backup of reference (file overwriting can still
occur). By default, files that have been destroyed
since the backup of reference are deleted during
restoration, but a warning is issued before
proceeding, except if -w is used. If -n is used, no
file will be deleted (nor overwritten), thus -k is
useless when using -n.
-r, --recent restore only files that are absent or more recent
than those present in filesystem. -r is useless if
-n is present.
-f, --flat do not restore directory structure. All file will
be restored in the directory given to -R, if two
files of the same name have to be restored, the
usual scheme for warning (-w option) and
overwriting (-n option) is used. No rename scheme
is planned actually. When this option is set, dar
does not remove files that have been stored as
deleted since last backup. (-f implicitly implies
-k).
-ae, --alter=erase_ea
Drop all existing EA of files present in filesystem
that will have to be restored. This way, the
restored files will have the exact set of EA they
had at the time of the backup. If this option is
not given, a file to restore will have its EA
overwritten by those present in the backup and if
some extra EAs are present they will remain
untouched. See the Note concerning Extended
Attributes (EA) above for a detailed explanation
about this behavior.
TESTING AND DIFFERENCE OPTIONS (to use with -t or -d)
No specific option, but all general options are available except -n and
-w which are useless, as testing and comparing only read data.
LISTING OPTIONS (to use with -l)
-T, --list-format=<normal | tree | xml>, --tree-format
By default, listing provides a tar-like output (the
’normal’ output). You can however get a tree-like
output (the ’tree’ output) or an XML structured
output (the ’xml’ output). Providing -T without
argument gives the same as providing the ’tree’
argument to it. The option --tree-format is an
alias to --list-format=tree (backward
compatibility). Note that the files doc/dar-
catalog-*.dtd define the format of the XML output
listing (This file is also installed under
$PREFIX/share/doc)
-as, --alter=saved list only saved files
-I and -X can be used to filter file to list base on their
name (is ignored when --list-format=tree is used).
Note that -P and -g options are not available while
listing.
Else only -v and -b from general options are useful. Note that -v
displays an archive summary first, where a lot of information about the
archive can be obtained.
displayed fields
[data] possible values are [ ] or [Saved] or [InRef] .
[ ] means that the data has not been saved
because there is no change since backup of
reference. [Saved] means that the data has been
saved, and thus this archive is able to restore the
file. [InRef] is used when isolating a catalogue
from an archive and means that the file was saved
in the reference archive.
[EA] possible values are " " (empty string) or [ ]
or [InRef] or [Saved]. It Shows if Extended
Attributes are present and saved ([Saved]), are
present but not saved ([ ]) which means there
is no change since backup of reference, or if there
is no EA saved for this file (empty string).
[InRef] is used when isolating a catalogue from an
archive and means that the file was saved in the
reference archive.
[compr] possible values are [....%] or [-----] or [ ]
or [worse]. Shows if the file has been compressed
and the compression rate reached ([...%]), or if
the file is stored without compression ([ ] see
-Y and -Z options) or if the file is not subject to
compression because it is not a saved regular file
([----]), or if the file takes more space
compressed than its original size ([worse]), due to
compression overhead.
permission
see ls man page.
user owner of the file
group group owner of the file
size size in byte of the file (if compression is
enabled, the real size in the archive is
"compression rate" time smaller).
date the last modification date of the file. The last
access time is also saved and restored, but not
displayed.
filename The name of the file.
EXPLICIT OPTIONAL ARGUMENTS
When dar has not been compiled with GNU getopt, which is not present by
default on some systems like FreeBSD, you may lack the optional
arguments syntax. For example "-z" will create a parse error on
command-line, or in -B configuration files. The solution is to
explicitly give the argument. Here follows a list of explicit argument
to use in place of optional ones:
-z must be replaced by -z 9
-y must be replaced by -y 9
-w must be replaced by -w d or -w default
-H must be replaced by -H 1
important ! When using GNU getopt(), optional arguments are available
by sticking the argument to the short option: "-z" for example is
available as well as "-z9". But "-z 9" is wrong, it will be read as
"-z" option and "9", a command line argument (not an argument to the -z
option). In the other side, when using a non GNU getopt this time, "-z"
becomes an option that always requires an argument, and thus "-z 9" is
read as "-z" option with "9" as argument, while "-z9" will be rejected
as a unknown option, and "-z" alone will generate an error as no
argument is provided. In consequences, you need a space between the
option (like "-z") and its argument (like "9"), when dar does not rely
on a GNU getopt() call, which also imply you to explicitly use
arguments to options listed just above.
EXIT CODES
dar exits with the following code:
0 Operation successful.
1 Syntax error on command-line.
2 Error due to a hardware problem or a lack of memory.
3 Detection of a condition that should never happen, and which
is considered as a bug of the application.
4 Code issued when the user has aborted the program upon dar
question from dar. This also happens when dar is not run from
a terminal (for example launched from crontab) and dar has a
question to the user. In that case, dar aborts the same way
as if the user pressed the escape key at the question prompt.
5 is returned when an error concerning the treated data has
been detected. While saving, this is the case when a file
could not be opened or read. While restoring, it is the case
when a file could not be created or replaced. While
comparing, it is the case when a file in the archive does not
match the one in the filesystem. While testing, it is the
case when a file is corrupted in the archive.
6 an error occurred while executing user command (given with -E
or -F option). Mainly because the creation of a new process
is not possible (process table is full) or the user command
returned an error code (exit status different of zero).
7 an error has occurred when calling a libdar routine. This
means the caller (dar program), did not respect the
specification of the API (and this can be considered as a
particular case of a bug).
8 the version of dar used is based in finite length integers
(it has been compiled with the option --enable-mode=...).
This code is returned when an integer overflow occurred. use
the full version (based in the so called "infinint" class) to
avoid this error.
9 this code indicates an unknown error. I have probably
forgotten to update the exception caching code to take care
of new exceptions... this is a minor bug you are welcome to
report.
10 you have tried to use a feature that has been disabled at
compilation time.
11 some saved files have changed while dar was reading them,
this may lead the data saved for this file not correspond to
a valid state for this file. For example, if the beginning
and the end of the file have been modified at the same time
(while dar is reading it), only the change at the end will be
saved (the beginning has already been read), the resulting
state of the file as recorded by dar has never existed and
may cause problem to the application using it.
SIGNALS
If dar receives a signal (see kill(2) man page) it will take the
default behavior which most of the time will abruptly abort the
program, except for the following signals:
SIGINT This signal is generated by the terminal when hitting CTRL-C
(with the terminal’s default settings), it can also be
generated with the kill command
SIGTERM This signal is generated by the system when changing of run-
level in particular when doing a shutdown, it can also be
generated with the kill command
SIGHUP Depending on the system, this signal may be sent before the
SIGTERM signal at shutdown time, it can also be generated
with the kill command
SIGQUIT This signal is generated by the terminal when hitting CTRL-\
(with the terminal’s default settings), it can also be
generated with the kill command
SIGUSR1 This signal can be generated by the kill command
SIGUSR2 This signal can be generated by the kill command
For those previous signals, two behavior exit. For SIGHUP, SIGINT,
SIGQUIT, SIGTERM and SIGUSR1, a delayed termination is done: the backup
or isolation operation is stopped, the catalogue is appended to the
archive and the archive is properly completed with the correct
terminator string, this way the generated archive is usable, and can be
used as reference for a differential backup at a later time. Note that
if an on-fly isolation had been asked, it will *not* be performed, and
no user command will be launched even if dar has been configured for
(-E option). For SIGUSR2 instead a fast termination is done: in case of
backup or isolation, the archive is not completed at all, only memory
and mutex are released properly.
For both type of termination and other operations than backup or
isolation, dar’s behavior is the same: For restoration, all opened
directories are closed and permissions are set back to their original
values (if they had to be changed for restoration). For listing,
comparison, testing, the program aborts immediately.
Another point, when using one of the previous signals, dar will return
with the exist status 4 meaning that the user has aborted the
operation. Note that answering "no" to a question from dar may also
lead dar to exit this way. last, If before the end of the program the
same signal is received a second time, dar will abort immediately.
FILES
$HOME/.darrc and /etc/darrc if present are read for configuration
option. They share the same syntax as file given to -B option. If
$HOME/.darrc is not present and only in that case, /etc/darrc is
consulted. You can still launch /etc/darrc from .darrc using a
statement like -B /etc/darrc. None of these file need to be present,
but if they are they are parsed AFTER any option on the command line
and AFTER included files from the command line (files given to the -B
option). NOTE: if $HOME is not defined $HOME/.darrc default to /.darrc
(at the root of the filesystem).
Else you can see conditional syntax bellow, and -N option above that
leads dar to ignore the /etc/darrc and $HOME/.darrc files.
CONDITIONAL SYNTAX
configuration files (-B option, $HOME/.darrc and /etc/darrc) usually
contain a simple list of command-line arguments, split or not over
several lines, and eventually mixed with comments (see -B option for
more). But, you can also use make-like targets to ask for a particular
set of commands to be used in certain conditions.
A condition takes the form of reserved word immediately followed by a
colon ’:’. This word + colon must stand alone on its line, eventually
with spaces or tabs beside it. The available conditions are:
extract: all option listed after this condition get used if
previously on command line or file the -x option
has been used
create: all option listed after this condition get used if
previously on command line or file (-B option) the
-c option has been used
listing: (or list:) if -l option has been used
test: if -t option has been used
diff: if -d option has been used
isolate: if -C option has been used
merge: if -+ option has been used
all: in any case
default: if no -c, -d, -x, -t, -C, -l or -+ option has been
used at this point of the parsing.
The condition stops when the next condition starts, or at End of File.
The commands inserted before any condition are equivalent to those
inserted after the "all:" condition. Remark : -c -d -x -t -C and -l are
mutual exclusive, only one of them can be used while calling dar.
Here is an example of conditional syntax
create:
# upon creation exclude the
# following files from compression
-Z "*.mp3" -Z "*.mpg"
all:
-b
-p
default:
# this will get read if not
# command has been set yet
-V
# thus by default dar shows its version
all:
-v
# for any command we also ask to be verbose
# this is added to the previous all: condition
Last point, you may have several time the same condition (several all:
) for example. They will be concatenated together.
EXAMPLES
You can find some more examples of use in the tutorial, mini-howto,
sample scripts, and other related documentation. All these are
available in dar’s source package, and are also installed beside dar in
the <--prefix>/share/dar directory. This documentation is also
available online at http://dar.linux.free.fr/doc/index.html#2
SEE ALSO
dar_xform(1), dar_slave(1), dar_manager(1), dar_cp(1)
see also TUTORIAL and NOTES files in the documentation.
KNOWN BUGS
dar cannot restore time of symbolic links. Many (all ?) UNIX do not
provide any way to do that, the utime() system call changes the file
pointed to by the link rather than the date of the link itself.
dar saves and restores atime and mtime, but cannot restore ctime (last
inode change), there does not seems to be a standard call to do that
under UNIX.
AUTHOR
http://dar.linux.free.fr/
Denis Corbin
France
Europe