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Archivage et Compression

Archivage

Afin de poursuivre, il convient de créer une arborescence à sauvegarder :

opensuse:~ # mkdir -p /test/repY; mkdir /test/repZ
opensuse:~ # cd /test/repY; touch Y1 Y2 Y3
opensuse:/test/repY # cd /test/repZ; touch Z1 Z2
opensuse:/test/repZ # ls -lR /test
/test:
total 8
drwxr-xr-x 2 root root 4096 Feb 1 12:08 repY
drwxr-xr-x 2 root root 4096 Feb 1 12:08 repZ
/test/repY:
total 0
-rw-r--r-- 1 root root 0 Feb 1 12:08 Y1
-rw-r--r-- 1 root root 0 Feb 1 12:08 Y2
-rw-r--r-- 1 root root 0 Feb 1 12:08 Y3
/test/repZ:
total 0
-rw-r--r-- 1 root root 0 Feb 1 12:08 Z1
-rw-r--r-- 1 root root 0 Feb 1 12:08 Z2

tar

Présentation

Le programme tar a été originellement prévu pour sauvegarder sur des bandes magnétiques, d'où son nom issu de tape archiver.

La commande tar peut sauvegarder vers :

un fichier spécial, par exemple le nom d'un lecteur de bande,

un fichier ordinaire sur disque,

la sortie standard pour être utilisé dans un pipe.

Options de la Commande

Les options de la commande tar sont :

opensuse:/test/repZ # tar --help
Usage: tar [OPTION...] [FILE]...
GNU `tar' saves many files together into a single tape or disk archive, and can
restore individual files from the archive.
Examples:
tar -cf archive.tar foo bar # Create archive.tar from files foo and bar.
tar -tvf archive.tar # List all files in archive.tar verbosely.
tar -xf archive.tar # Extract all files from archive.tar.
Main operation mode:
-A, --catenate, --concatenate append tar files to an archive
-c, --create create a new archive
-d, --diff, --compare find differences between archive and file system
--delete delete from the archive (not on mag tapes!)
-r, --append append files to the end of an archive
-t, --list list the contents of an archive
--test-label test the archive volume label and exit
-u, --update only append files newer than copy in archive
-x, --extract, --get extract files from an archive
Operation modifiers:
--check-device check device numbers when creating incremental
archives (default)
-g, --listed-incremental=FILE handle new GNU-format incremental backup
-G, --incremental handle old GNU-format incremental backup
--ignore-failed-read do not exit with nonzero on unreadable files
--level=NUMBER dump level for created listed-incremental archive
-n, --seek archive is seekable
--no-check-device do not check device numbers when creating
incremental archives
--no-seek archive is not seekable
--occurrence[=NUMBER] process only the NUMBERth occurrence of each file
in the archive; this option is valid only in
conjunction with one of the subcommands --delete,
--diff, --extract or --list and when a list of
files is given either on the command line or via
the -T option; NUMBER defaults to 1
--sparse-version=MAJOR[.MINOR]
set version of the sparse format to use (implies
--sparse)
-S, --sparse handle sparse files efficiently
Overwrite control:
-k, --keep-old-files don't replace existing files when extracting
--keep-newer-files don't replace existing files that are newer than
their archive copies
--no-overwrite-dir preserve metadata of existing directories
--overwrite overwrite existing files when extracting
--overwrite-dir overwrite metadata of existing directories when
extracting (default)
--recursive-unlink empty hierarchies prior to extracting directory
--remove-files remove files after adding them to the archive
-U, --unlink-first remove each file prior to extracting over it
-W, --verify attempt to verify the archive after writing it
Select output stream:
--ignore-command-error ignore exit codes of children
--no-ignore-command-error treat non-zero exit codes of children as
error
-O, --to-stdout extract files to standard output
--to-command=COMMAND pipe extracted files to another program
Handling of file attributes:
--atime-preserve[=METHOD] preserve access times on dumped files, either
by restoring the times after reading
(METHOD='replace'; default) or by not setting the
times in the first place (METHOD='system')
--delay-directory-restore delay setting modification times and
permissions of extracted directories until the end
of extraction
--group=NAME force NAME as group for added files
--mode=CHANGES force (symbolic) mode CHANGES for added files
--mtime=DATE-OR-FILE set mtime for added files from DATE-OR-FILE
-m, --touch don't extract file modified time
--no-delay-directory-restore
cancel the effect of --delay-directory-restore
option
--no-same-owner extract files as yourself (default for ordinary
users)
--no-same-permissions apply the user's umask when extracting permissions
from the archive (default for ordinary users)
--numeric-owner always use numbers for user/group names
--owner=NAME force NAME as owner for added files
-p, --preserve-permissions, --same-permissions
extract information about file permissions
(default for superuser)
--preserve same as both -p and -s
--same-owner try extracting files with the same ownership as
exists in the archive (default for superuser)
-s, --preserve-order, --same-order
sort names to extract to match archive
Device selection and switching:
-f, --file=ARCHIVE use archive file or device ARCHIVE
--force-local archive file is local even if it has a colon
-F, --info-script=NAME, --new-volume-script=NAME
run script at end of each tape (implies -M)
-L, --tape-length=NUMBER change tape after writing NUMBER x 1024 bytes
-M, --multi-volume create/list/extract multi-volume archive
--rmt-command=COMMAND use given rmt COMMAND instead of rmt
--rsh-command=COMMAND use remote COMMAND instead of rsh
--volno-file=FILE use/update the volume number in FILE
Device blocking:
-b, --blocking-factor=BLOCKS BLOCKS x 512 bytes per record
-B, --read-full-records reblock as we read (for 4.2BSD pipes)
-i, --ignore-zeros ignore zeroed blocks in archive (means EOF)
--record-size=NUMBER NUMBER of bytes per record, multiple of 512
Archive format selection:
-H, --format=FORMAT create archive of the given format
FORMAT is one of the following:
gnu GNU tar 1.13.x format
oldgnu GNU format as per tar <= 1.12
pax POSIX 1003.1-2001 (pax) format
posix same as pax
ustar POSIX 1003.1-1988 (ustar) format
v7 old V7 tar format
--old-archive, --portability
same as --format=v7
--pax-option=keyword[[:]=value][,keyword[[:]=value]]...
control pax keywords
--posix same as --format=posix
-V, --label=TEXT create archive with volume name TEXT; at
list/extract time, use TEXT as a globbing pattern
for volume name
Compression options:
-a, --auto-compress use archive suffix to determine the compression
program
-I, --use-compress-program=PROG
filter through PROG (must accept -d)
-j, --bzip2 filter the archive through bzip2
-J, --xz filter the archive through xz
--lzip filter the archive through lzip
--lzma filter the archive through lzma
--lzop
--no-auto-compress do not use archive suffix to determine the
compression program
-z, --gzip, --gunzip, --ungzip filter the archive through gzip
-Z, --compress, --uncompress filter the archive through compress
Local file selection:
--add-file=FILE add given FILE to the archive (useful if its name
starts with a dash)
--backup[=CONTROL] backup before removal, choose version CONTROL
-C, --directory=DIR change to directory DIR
--exclude=PATTERN exclude files, given as a PATTERN
--exclude-backups exclude backup and lock files
--exclude-caches exclude contents of directories containing
CACHEDIR.TAG, except for the tag file itself
--exclude-caches-all exclude directories containing CACHEDIR.TAG
--exclude-caches-under exclude everything under directories containing
CACHEDIR.TAG
--exclude-tag=FILE exclude contents of directories containing FILE,
except for FILE itself
--exclude-tag-all=FILE exclude directories containing FILE
--exclude-tag-under=FILE exclude everything under directories
containing FILE
--exclude-vcs exclude version control system directories
-h, --dereference follow symlinks; archive and dump the files they
point to
--hard-dereference follow hard links; archive and dump the files they
refer to
-K, --starting-file=MEMBER-NAME
begin at member MEMBER-NAME in the archive
--newer-mtime=DATE compare date and time when data changed only
--no-null disable the effect of the previous --null option
--no-recursion avoid descending automatically in directories
--no-unquote do not unquote filenames read with -T
--null -T reads null-terminated names, disable -C
-N, --newer=DATE-OR-FILE, --after-date=DATE-OR-FILE
only store files newer than DATE-OR-FILE
--one-file-system stay in local file system when creating archive
-P, --absolute-names don't strip leading `/'s from file names
--recursion recurse into directories (default)
--suffix=STRING backup before removal, override usual suffix ('~'
unless overridden by environment variable
SIMPLE_BACKUP_SUFFIX)
-T, --files-from=FILE get names to extract or create from FILE
--unquote unquote filenames read with -T (default)
-X, --exclude-from=FILE exclude patterns listed in FILE
File name transformations:
--strip-components=NUMBER strip NUMBER leading components from file
names on extraction
--transform=EXPRESSION, --xform=EXPRESSION
use sed replace EXPRESSION to transform file
names
File name matching options (affect both exclude and include patterns):
--anchored patterns match file name start
--ignore-case ignore case
--no-anchored patterns match after any `/' (default for
exclusion)
--no-ignore-case case sensitive matching (default)
--no-wildcards verbatim string matching
--no-wildcards-match-slash wildcards do not match `/'
--wildcards use wildcards (default for exclusion)
--wildcards-match-slash wildcards match `/' (default for exclusion)
Informative output:
--checkpoint[=NUMBER] display progress messages every NUMBERth record
(default 10)
--checkpoint-action=ACTION execute ACTION on each checkpoint
--full-time print file time to its full resolution
--index-file=FILE send verbose output to FILE
-l, --check-links print a message if not all links are dumped
--no-quote-chars=STRING disable quoting for characters from STRING
--quote-chars=STRING additionally quote characters from STRING
--quoting-style=STYLE set name quoting style; see below for valid STYLE
values
-R, --block-number show block number within archive with each
message
--show-defaults show tar defaults
--show-omitted-dirs when listing or extracting, list each directory
that does not match search criteria
--show-transformed-names, --show-stored-names
show file or archive names after transformation
--totals[=SIGNAL] print total bytes after processing the archive;
with an argument - print total bytes when this
SIGNAL is delivered; Allowed signals are: SIGHUP,
SIGQUIT, SIGINT, SIGUSR1 and SIGUSR2; the names
without SIG prefix are also accepted
--utc print file modification times in UTC
-v, --verbose verbosely list files processed
--warning=KEYWORD warning control
-w, --interactive, --confirmation
ask for confirmation for every action
Compatibility options:
-o when creating, same as --old-archive; when
extracting, same as --no-same-owner
Other options:
-?, --help give this help list
--restrict disable use of some potentially harmful options
--usage give a short usage message
--version print program version
Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.
The backup suffix is `~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.
The version control may be set with --backup or VERSION_CONTROL, values are:
none, off never make backups
t, numbered make numbered backups
nil, existing numbered if numbered backups exist, simple otherwise
never, simple always make simple backups
Valid arguments for the --quoting-style option are:
literal
shell
shell-always
c
c-maybe
escape
locale
clocale
*This* tar defaults to:
--format=gnu -f- -b20 --quoting-style=escape --rmt-command=/usr/lib/rmt
--rsh-command=/usr/bin/rsh
Report bugs to <bug-tar@gnu.org>.

Exercices

Vous allez maintenant sauvegarder votre dossier test ainsi que son contenu vers un fichier :

opensuse:/test/repZ # tar cvf /tmp/test.tar /test
tar: Removing leading `/' from member names
/test/
/test/repY/
/test/repY/Y1
/test/repY/Y3
/test/repY/Y2
/test/repZ/
/test/repZ/Z1
/test/repZ/Z2

Pour visualiser la table of contents de votre sauvegarde, utilisez la commande suivante :

opensuse:/test/repZ # tar tvf /tmp/test.tar
drwxr-xr-x root/root 0 2012-02-01 12:07 test/
drwxr-xr-x root/root 0 2012-02-01 12:08 test/repY/
-rw-r--r-- root/root 0 2012-02-01 12:08 test/repY/Y1
-rw-r--r-- root/root 0 2012-02-01 12:08 test/repY/Y3
-rw-r--r-- root/root 0 2012-02-01 12:08 test/repY/Y2
drwxr-xr-x root/root 0 2012-02-01 12:08 test/repZ/
-rw-r--r-- root/root 0 2012-02-01 12:08 test/repZ/Z1
-rw-r--r-- root/root 0 2012-02-01 12:08 test/repZ/Z2

Afin de créer une sauvegarde incrémentale, vous avez besoin de créer un fichier qui servira de référence de date :

opensuse:/test/repZ # touch /tmp/dateref

Modifiez maintenant deux des fichiers de votre arborescence test :

opensuse:/test/repZ # echo "openSUSE est super \!" > /test/repY/Y1
opensuse:/test/repZ # echo "openSUSE is wonderful \!" > /test/repZ/Z1

Pour procéder à votre sauvegarde incrémentale, vous devez sauvegarder uniquement les fichiers modifiés ou créés depuis la création de votre fichier /tmp/dateref.

Saisissez donc la commande suivante :

opensuse:/test/repZ # tar -cvf /tmp/incremental.tar -N /tmp/dateref /test
tar: Removing leading `/' from member names
/test/
/test/repY/
/test/repY/Y1
tar: /test/repY/Y3: file is unchanged; not dumped
tar: /test/repY/Y2: file is unchanged; not dumped
/test/repZ/
/test/repZ/Z1
tar: /test/repZ/Z2: file is unchanged; not dumped

<note important> Notez l'utilisation de l'option -N avec l'arguement /tmp/dateref qui pezrmet d'identifier les fichiers modifiés ou créés depuis la création de /tmp/dateref. </note>

Contrôlez maintenant le contenu de l'archive /tmp/incremental.tar :

opensuse:/test/repZ # tar tvf /tmp/incremental.tar
drwxr-xr-x root/root 0 2012-02-01 12:07 test/
drwxr-xr-x root/root 0 2012-02-01 12:08 test/repY/
-rw-r--r-- root/root 22 2012-02-01 17:00 test/repY/Y1
drwxr-xr-x root/root 0 2012-02-01 12:08 test/repZ/
-rw-r--r-- root/root 25 2012-02-01 17:00 test/repZ/Z1

Supprimez maintenant le contenu du répertoire test :

opensuse:/test/repZ # rm -rf /test/*

<note important> Notez que le système vous permet de supprimer le répertoire /test/repZ, or vous vous situez dans ce même répertoire ! </note>

Afin de pouvoir restaurer les fichiers de votre première sauvegarde, placez-vous à la racine de votre système et restaurez le contenu de votre répertoire test en saisissant la commande tar suivante :

opensuse:/test/repZ # cd /
opensuse:/ # tar xvf /tmp/test.tar
test/
test/repY/
test/repY/Y1
test/repY/Y3
test/repY/Y2
test/repZ/
test/repZ/Z1
test/repZ/Z2

Constatez maintenant que l'opération s'est bien déroulée :

opensuse:/ # ls -lR /test
/test:
total 8
drwxr-xr-x 2 root root 4096 Feb 1 12:08 repY
drwxr-xr-x 2 root root 4096 Feb 1 12:08 repZ
/test/repY:
total 0
-rw-r--r-- 1 root root 0 Feb 1 12:08 Y1
-rw-r--r-- 1 root root 0 Feb 1 12:08 Y2
-rw-r--r-- 1 root root 0 Feb 1 12:08 Y3
/test/repZ:
total 0
-rw-r--r-- 1 root root 0 Feb 1 12:08 Z1
-rw-r--r-- 1 root root 0 Feb 1 12:08 Z2

<note important> Notez qu'à ce stade les fichiers /test/repY/Y1 et /test/repZ/Z1 sont vides. </note>

Restaurez maintenant votre archive incrémentale :

opensuse:/ # tar xvf /tmp/incremental.tar
test/
test/repY/
test/repY/Y1
test/repZ/
test/repZ/Z1

Constatez maintenant que l'opération s'est bien déroulée :

opensuse:/ # ls -lR /test
/test:
total 8
drwxr-xr-x 2 root root 4096 Feb 1 12:08 repY
drwxr-xr-x 2 root root 4096 Feb 1 12:08 repZ
/test/repY:
total 4
-rw-r--r-- 1 root root 22 Feb 1 17:00 Y1
-rw-r--r-- 1 root root 0 Feb 1 12:08 Y2
-rw-r--r-- 1 root root 0 Feb 1 12:08 Y3
/test/repZ:
total 4
-rw-r--r-- 1 root root 25 Feb 1 17:00 Z1
-rw-r--r-- 1 root root 0 Feb 1 12:08 Z2

<note important> Notez que les fichiers /test/repY/Y1 et /test/repZ/Z1 sont maintenant non-vides. </note>

cpio

Présentation

La commande cpio (Copy Input To Output). cpio peut gérer les archives au format tar. La différence majeure entre tar et cpio est que ce dernier stocke les chemins d'accès aux fichiers sauvgardés en même temps que les fichiers eux-mêmes. Ceci implique que dans le cas où le chemin absolu a été spécifié lors de la sauvegarde, il est impossible de restaurer un fichier à un autre emplacement que son emplacement d'origine.

Vous allez utiliser maintenant le logiciel cpio pour effectuer les sauvegardes et restaurations.

Options de la Commande

Les options de la commande cpio sont :

opensuse:/ # cpio --help
Usage: cpio [OPTION...] [destination-directory]
GNU `cpio' copies files to and from archives
Examples:
# Copy files named in name-list to the archive
cpio -o < name-list [> archive]
# Extract files from the archive
cpio -i [< archive]
# Copy files named in name-list to destination-directory
cpio -p destination-directory < name-list
Main operation mode:
-i, --extract Extract files from an archive (run in copy-in
mode)
-o, --create Create the archive (run in copy-out mode)
-p, --pass-through Run in copy-pass mode
-t, --list Print a table of contents of the input
Operation modifiers valid in any mode:
--block-size=BLOCK-SIZE Set the I/O block size to BLOCK-SIZE * 512
bytes
-B Set the I/O block size to 5120 bytes
-c Use the old portable (ASCII) archive format
-C, --io-size=NUMBER Set the I/O block size to the given NUMBER of
bytes
--force-local Archive file is local, even if its name contains
colons
-f, --nonmatching Only copy files that do not match any of the given
patterns
-F, --file=[[USER@]HOST:]FILE-NAME
Use this FILE-NAME instead of standard input or
output. Optional USER and HOST specify the user
and host names in case of a remote archive
-H, --format=FORMAT Use given archive FORMAT
-M, --message=STRING Print STRING when the end of a volume of the
backup media is reached
-n, --numeric-uid-gid In the verbose table of contents listing, show
numeric UID and GID
--quiet Do not print the number of blocks copied
--rsh-command=COMMAND Use remote COMMAND instead of rsh
-v, --verbose Verbosely list the files processed
-V, --dot Print a "." for each file processed
-W, --warning=FLAG Control warning display. Currently FLAG is one of
'none', 'truncate', 'all'. Multiple options
accumulate.
Operation modifiers valid only in copy-in mode:
-b, --swap Swap both halfwords of words and bytes of
halfwords in the data. Equivalent to -sS
-r, --rename Interactively rename files
-s, --swap-bytes Swap the bytes of each halfword in the files
-S, --swap-halfwords Swap the halfwords of each word (4 bytes) in the
files
--to-stdout Extract files to standard output
-E, --pattern-file=FILE Read additional patterns specifying filenames to
extract or list from FILE
--only-verify-crc When reading a CRC format archive, only verify the
CRC's of each file in the archive, don't actually
extract the files
Operation modifiers valid only in copy-out mode:
-A, --append Append to an existing archive.
-O [[USER@]HOST:]FILE-NAME Archive filename to use instead of standard
output. Optional USER and HOST specify the user
and host names in case of a remote archive
Operation modifiers valid only in copy-pass mode:
-l, --link Link files instead of copying them, when
possible
Operation modifiers valid in copy-in and copy-out modes:
--absolute-filenames Do not strip file system prefix components from
the file names
--no-absolute-filenames Create all files relative to the current
directory
Operation modifiers valid in copy-out and copy-pass modes:
-0, --null A list of filenames is terminated by a null
character instead of a newline
-a, --reset-access-time Reset the access times of files after reading them
-I [[USER@]HOST:]FILE-NAME Archive filename to use instead of standard input.
Optional USER and HOST specify the user and host
names in case of a remote archive
-L, --dereference Dereference symbolic links (copy the files
that they point to instead of copying the links).
-R, --owner=[USER][:.][GROUP] Set the ownership of all files created to the
specified USER and/or GROUP
Operation modifiers valid in copy-in and copy-pass modes:
-d, --make-directories Create leading directories where needed
-m, --preserve-modification-time
Retain previous file modification times when
creating files
--no-preserve-owner Do not change the ownership of the files
--sparse Write files with large blocks of zeros as sparse
files
-u, --unconditional Replace all files unconditionally
-?, --help give this help list
--usage give a short usage message
--version print program version
Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.
Report bugs to <bug-cpio@gnu.org>.

Exercices

Dans un premier temps, vous devez utiliser la commande find pour construire une liste de fichiers à sauvegarder :

opensuse:/ # find /test > /tmp/cpio.liste
opensuse:/ # cat /tmp/cpio.liste
/test
/test/repY
/test/repY/Y1
/test/repY/Y3
/test/repY/Y2
/test/repZ
/test/repZ/Z1
/test/repZ/Z2

Sauvegardez maintenant les fichiers et répertoires référencés par le fichier /tmp/cpio.liste :

opensuse:/ # cpio -ov < /tmp/cpio.liste > /tmp/test.cpio
/test
/test/repY
/test/repY/Y1
/test/repY/Y3
/test/repY/Y2
/test/repZ
/test/repZ/Z1
/test/repZ/Z2
1 block

Consultez maintenant la table of contents de votre sauvegarde :

opensuse:/ # cpio -it < /tmp/test.cpio
/test
/test/repY
/test/repY/Y1
/test/repY/Y3
/test/repY/Y2
/test/repZ
/test/repZ/Z1
/test/repZ/Z2
1 block

Supprimez maintenant le répertoire /test/repY et son contenu :

opensuse:/ # rm -rf /test/repY

Contrôlez le bon déroulement de la suppression :

opensuse:/ # ls -lR /test
/test:
total 4
drwxr-xr-x 2 root root 4096 Feb 1 12:08 repZ
/test/repZ:
total 4
-rw-r--r-- 1 root root 25 Feb 1 17:00 Z1
-rw-r--r-- 1 root root 0 Feb 1 12:08 Z2

Restaurez les fichiers supprimés :

opensuse:/ # cpio -ivdum "/test/repY/*" < /tmp/test.cpio
/test/repY/Y1
/test/repY/Y3
/test/repY/Y2
1 block

<note important> Notez l'utilisation de la chaîne “/test/repY/*” qui permet de rechercher uniquement le répertoire repY ainsi que les fichiers Y1, Y2 et Y3 dans l'archive test.cpio. </note>

Contrôlez le bon déroulement de la restauration :

opensuse:/ # ls -lR /test
/test:
total 8
drwx------ 2 root root 4096 Feb 1 17:07 repY
drwxr-xr-x 2 root root 4096 Feb 1 12:08 repZ
/test/repY:
total 4
-rw-r--r-- 1 root root 22 Feb 1 17:00 Y1
-rw-r--r-- 1 root root 0 Feb 1 12:08 Y2
-rw-r--r-- 1 root root 0 Feb 1 12:08 Y3
/test/repZ:
total 4
-rw-r--r-- 1 root root 25 Feb 1 17:00 Z1
-rw-r--r-- 1 root root 0 Feb 1 12:08 Z2

dd

Présentation

La commande dd n'est pas réellement une commande de sauvegarde.

La commande dd copie le fichier passé en entrée dans le fichier de sortie en limitant le nombre d'octets copiés par l'utilisation de deux options :

count

le nombre

bs

la taille du bloc à copier

Options de la Commande

Les options de la commande dd sont :

opensuse:/ # dd --help
Usage: dd [OPERAND]...
or: dd OPTION
Copy a file, converting and formatting according to the operands.
bs=BYTES read and write BYTES bytes at a time (also see ibs=,obs=)
cbs=BYTES convert BYTES bytes at a time
conv=CONVS convert the file as per the comma separated symbol list
count=BLOCKS copy only BLOCKS input blocks
ibs=BYTES read BYTES bytes at a time (default: 512)
if=FILE read from FILE instead of stdin
iflag=FLAGS read as per the comma separated symbol list
obs=BYTES write BYTES bytes at a time (default: 512)
of=FILE write to FILE instead of stdout
oflag=FLAGS write as per the comma separated symbol list
seek=BLOCKS skip BLOCKS obs-sized blocks at start of output
skip=BLOCKS skip BLOCKS ibs-sized blocks at start of input
status=noxfer suppress transfer statistics
BLOCKS and BYTES may be followed by the following multiplicative suffixes:
c =1, w =2, b =512, kB =1000, K =1024, MB =1000*1000, M =1024*1024, xM =M
GB =1000*1000*1000, G =1024*1024*1024, and so on for T, P, E, Z, Y.
Each CONV symbol may be:
ascii from EBCDIC to ASCII
ebcdic from ASCII to EBCDIC
ibm from ASCII to alternate EBCDIC
block pad newline-terminated records with spaces to cbs-size
unblock replace trailing spaces in cbs-size records with newline
lcase change upper case to lower case
nocreat do not create the output file
excl fail if the output file already exists
notrunc do not truncate the output file
ucase change lower case to upper case
swab swap every pair of input bytes
noerror continue after read errors
sync pad every input block with NULs to ibs-size; when used
with block or unblock, pad with spaces rather than NULs
fdatasync physically write output file data before finishing
fsync likewise, but also write metadata
Each FLAG symbol may be:
append append mode (makes sense only for output; conv=notrunc suggested)
direct use direct I/O for data
directory fail unless a directory
dsync use synchronized I/O for data
sync likewise, but also for metadata
fullblock accumulate full blocks of input (iflag only)
nonblock use non-blocking I/O
noatime do not update access time
noctty do not assign controlling terminal from file
nofollow do not follow symlinks
Sending a USR1 signal to a running `dd' process makes it
print I/O statistics to standard error and then resume copying.
$ dd if=/dev/zero of=/dev/null& pid=$!
$ kill -USR1 $pid; sleep 1; kill $pid
18335302+0 records in
18335302+0 records out
9387674624 bytes (9.4 GB) copied, 34.6279 seconds, 271 MB/s
Options are:
--help display this help and exit
--version output version information and exit
Report dd bugs to bug-coreutils@gnu.org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
Report dd translation bugs to <http://translationproject.org/team/>
For complete documentation, run: info coreutils 'dd invocation'

Exercices

Vous allez utiliser maintenant le logiciel dd pour effectuer une sauvegarde de votre MBR et de la FAT.

Effectuez une sauvegarde de votre MBR qui se trouve dans les premiers 446 octets de votre disque /dev/sda :

opensuse:/ # dd if=/dev/sda of=/tmp/mbr.save bs=1 count=446
446+0 records in
446+0 records out
446 bytes (446 B) copied, 0.00283065 s, 158 kB/s

Effectuez maintenant une sauvegarde de votre FAT qui se trouve dans les 64 octets après les 446 précédement sauvegardés :

opensuse:/ # dd if=/dev/sda of=/tmp/fat.save bs=1 count=64 skip=446
64+0 records in
64+0 records out
64 bytes (64 B) copied, 0.000208915 s, 306 kB/s

<note important> Notez l'utilisation de l'option skip qui permet de positionner le début de la sauvegarde au 447ième octet. </note>

dump et restore

Présentation

Les commandes dump et restore se basent sur le format d'enregistrement des données ( ext3 ). Pour cette raison il n'est pas possible de sauvegarder des répertoires à l'intérieur d'un système de fichiers mais uniquement des systèmes de fichiers complets.

Il est important de noter que le système de fichier ne doit pas être utilisé pendant le processus de dump. Pour cette raison il est normalement conseillé de démonter le système de fichiers.

Il existe 10 niveaux de dump possibles de 0 à 9. Lors d'un dump le niveau est spécifié. Chaque fois qu'un dump est effectué, cette information est sauvegardée dans le fichier /etc/dumpdates.

Par définition un dump de niveau 0 est une sauvegarde complète tandis que le dump de niveau 1 est une sauvegarde incrémentale.

Notez que les fichiers sont sauvegardés avec des nom relatifs. Ceci implique que vous devez vous positionner dans le système de fichiers lors de la restauration avec la commande restore.

Compression

gzip

Présentation

La commande gzip est un utilitaire de compression sous GNU/Linux. La commande gunzip est un utilitaire de décompression sous GNU/Linux.

Options des Commandes

Les options de la commande gzip sont :

opensuse:/ # gzip --help
Usage: gzip [OPTION]... [FILE]...
Compress or uncompress FILEs (by default, compress FILES in-place).
Mandatory arguments to long options are mandatory for short options too.
-c, --stdout write on standard output, keep original files unchanged
-d, --decompress decompress
-f, --force force overwrite of output file and compress links
-h, --help give this help
-l, --list list compressed file contents
-L, --license display software license
-n, --no-name do not save or restore the original name and time stamp
-N, --name save or restore the original name and time stamp
-q, --quiet suppress all warnings
-r, --recursive operate recursively on directories
-S, --suffix=SUF use suffix SUF on compressed files
-t, --test test compressed file integrity
-v, --verbose verbose mode
-V, --version display version number
-1, --fast compress faster
-9, --best compress better
--rsyncable Make rsync-friendly archive
With no FILE, or when FILE is -, read standard input.
Report bugs to <bug-gzip@gnu.org>.

Les options de la commande gunzip sont :

opensuse:/ # gunzip --help
Usage: /usr/bin/gunzip [OPTION]... [FILE]...
Uncompress FILEs (by default, in-place).
Mandatory arguments to long options are mandatory for short options too.
-c, --stdout write on standard output, keep original files unchanged
-f, --force force overwrite of output file and compress links
-l, --list list compressed file contents
-n, --no-name do not save or restore the original name and time stamp
-N, --name save or restore the original name and time stamp
-q, --quiet suppress all warnings
-r, --recursive operate recursively on directories
-S, --suffix=SUF use suffix SUF on compressed files
-t, --test test compressed file integrity
-v, --verbose verbose mode
--help display this help and exit
--version display version information and exit
With no FILE, or when FILE is -, read standard input.
Report bugs to <bug-gzip@gnu.org>.

Exercices

Utilisez gzip pour compresser votre fichier tar :

opensuse:/ # gzip /tmp/test.tar

Constatez la taille du fichier test.tar.gz :

opensuse:/ # ls -l /tmp/test.tar.gz
-rw-r--r-- 1 root root 221 Feb 1 16:57 /tmp/test.tar.gz

<note important> Notez que le fichier compressé a été créé dans le même répertoire que le fichier source et que le fichier source a disparu. </note>

Décompressez le fichier test.tar.gz :

opensuse:/ # gunzip /tmp/test.tar.gz

bzip2

Présentation

La commande bzip2 est un utilitaire de compression sous GNU/Linux. La commande bunzip2 est un utilitaire de décompression sous GNU/Linux.

Options des Commandes

Les options de la commande bzip2 sont :

opensuse:/ # bzip2 --help
bzip2, a block-sorting file compressor. Version 1.0.6, 6-Sept-2010.
usage: bzip2 [flags and input files in any order]
-h --help print this message
-d --decompress force decompression
-z --compress force compression
-k --keep keep (don't delete) input files
-f --force overwrite existing output files
-t --test test compressed file integrity
-c --stdout output to standard out
-q --quiet suppress noncritical error messages
-v --verbose be verbose (a 2nd -v gives more)
-L --license display software version & license
-V --version display software version & license
-s --small use less memory (at most 2500k)
-1 .. -9 set block size to 100k .. 900k
--fast alias for -1
--best alias for -9
If invoked as `bzip2', default action is to compress.
as `bunzip2', default action is to decompress.
as `bzcat', default action is to decompress to stdout.
If no file names are given, bzip2 compresses or decompresses
from standard input to standard output. You can combine
short flags, so `-v -4' means the same as -v4 or -4v, &c.

Les options de la commande bunzip2 sont :

opensuse:/ # bunzip2 --help
bzip2, a block-sorting file compressor. Version 1.0.6, 6-Sept-2010.
usage: bunzip2 [flags and input files in any order]
-h --help print this message
-d --decompress force decompression
-z --compress force compression
-k --keep keep (don't delete) input files
-f --force overwrite existing output files
-t --test test compressed file integrity
-c --stdout output to standard out
-q --quiet suppress noncritical error messages
-v --verbose be verbose (a 2nd -v gives more)
-L --license display software version & license
-V --version display software version & license
-s --small use less memory (at most 2500k)
-1 .. -9 set block size to 100k .. 900k
--fast alias for -1
--best alias for -9
If invoked as `bzip2', default action is to compress.
as `bunzip2', default action is to decompress.
as `bzcat', default action is to decompress to stdout.
If no file names are given, bzip2 compresses or decompresses
from standard input to standard output. You can combine
short flags, so `-v -4' means the same as -v4 or -4v, &c.

Exercices

Utilisez bzip2 pour compresser votre fichier tar :

opensuse:/ # bzip2 /tmp/test.tar

Constatez la taille du fichier tar.bz2 :

opensuse:/ # ls -l /tmp | grep test.tar.bz2
-rw-r--r-- 1 root root 199 Feb 1 16:57 test.tar.bz2

<note important> Notez que le fichier compressé a été créé dans le même répertoire que le fichier source et que le fichier source a disparu. </note>

Décompressez le fichier tar.bz2 :

opensuse:/ # bunzip2 /tmp/test.tar.bz2

<note important> La commande compress peut également être utilisée pour compresser un fichier. </note>

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