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DAR

DAR

Section: User Commands (1) Updated: May 21st, 2009
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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


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
EXPLICIT OPTIONAL ARGUMENTS
EXIT CODES
SIGNALS
FILES
CONDITIONAL SYNTAX
EXAMPLES
SEE ALSO
KNOWN BUGS
AUTHOR

This document was created by man2html, using the manual pages.
Time: 21:10:13 GMT, April 16, 2011