Linuxサーバのバックアップにはよくdumpが使われたりするけれども、それよりもrsyncの方が幸せになれると思う。
ネットワーク経由やssh経由でバックアップできるのがすばらしい。
もちろんローカルのメディアにバックアップすることも可能。
更に差分バックアップなので、時間が食われるのは最初だけ。
Heartbeatなんかを使ってレプリケーションするのも手だが、レプリケーションは個人ユースではまあ不要だろう。

rsyncの使い方は基本的にはcron.dailyあたりにつっこんで回す感じになるだろうけど、rsync自体のオプションがやたらとあって一見ややこしい。
けど、単純に使いたいならとりあえず-aオプションつけてればいい。
そのほかは個人の好みによるカスタマイズのためについているオプションだと思っていいだろう。

オプションの一覧はrsync –helpででてくる。
なげーんで最後に張っておく。

で、-aは-rlptgoDと等しく、どういうオプションかっていうとこうなる。
再帰的に(r)シンボリックリンクはシンボリックリンクとして(l)パーミッションを保持しつつ(p)更新日時を保持しつつ(t)グループと(g)オーナーを保持しつつ(o)デバイスと特殊ファイルを保持する(D=–devices –specials)。

オプションの意味さえ理解すれば使い方は非常に簡単で、たとえばsshで自分のとこのHDDに対象サーバのバックアップをとりたいなら、

rsync -a USERNAME@ssh.example.com:dir/BACKUP/SOURCE/DIR /BACKUP/TARGET/DIR

とかやればまるっととれる。

感覚としてはcpコマンドと同じ感覚である。
ssh-agentを使ってパスフレーズレスで接続できるようにしておけば、リモートのサーバのバックアップもcronで簡単にできるわけだ。
ただ、cpと違う部分は、ディレクトリ末の/の取り扱い。
rsync dirA/ dirB/
と
rsync dirA dirB
は挙動が違う。
前者は
cp -pr dirA/* dirB/
後者は
cp -pr dirA dirB
だと思っていい。
つまり、コピー元のディレクトリの最後に/をつけると、そのディレクトリ以下からコピーされ、つけないとディレクトリごとコピーされる。
コピー先はどっちでも影響ない。

あと、sshなどによるリモート接続でrsyncでバックアップを行う場合、双方にrsyncが入っている必要がある。
といっても今のlinuxシステムはデフォルトで入ってるかaptなりyumなりですぐ手にはいるだろう。

で、人によって必要となるオプションは変わってくるんで、その辺はオプション一覧を眺めてもらうとして、うちではこういう感じ。

rsync -a –delete-after –exclude ‘*~’ –exclude ‘*.swp’ –exclude ‘*.pid’ コピー元 コピー先

あとは/etc/cron.dailyに適当にファイル作って

#!/bin/sh

test -x /usr/bin/rsync || exit 0
/usr/bin/rsync -a –delete-after –exclude ‘*~’ –exclude ‘*.swp’ –exclude ‘*.pid’ コピー元 コピー先

とか書いておけば幸せになれる。

# rsync –help
rsync  version 3.0.5  protocol version 30
Copyright (C) 1996-2008 by Andrew Tridgell, Wayne Davison, and others.
Web site: http://rsync.samba.org/
Capabilities:
64-bit files, 64-bit inums, 64-bit timestamps, 64-bit long ints,
socketpairs, hardlinks, symlinks, IPv6, batchfiles, inplace,
append, ACLs, xattrs, iconv, symtimes

rsync comes with ABSOLUTELY NO WARRANTY.  This is free software, and you
are welcome to redistribute it under certain conditions.  See the GNU
General Public Licence for details.

rsync is a file transfer program capable of efficient remote update
via a fast differencing algorithm.

Usage: rsync [OPTION]… SRC [SRC]… DEST
or   rsync [OPTION]… SRC [SRC]… [USER@]HOST:DEST
or   rsync [OPTION]… SRC [SRC]… [USER@]HOST::DEST
or   rsync [OPTION]… SRC [SRC]… rsync://[USER@]HOST[:PORT]/DEST
or   rsync [OPTION]… [USER@]HOST:SRC [DEST]
or   rsync [OPTION]… [USER@]HOST::SRC [DEST]
or   rsync [OPTION]… rsync://[USER@]HOST[:PORT]/SRC [DEST]
The ‘:’ usages connect via remote shell, while ‘::’ & ‘rsync://’ usages connect
to an rsync daemon, and require SRC or DEST to start with a module name.

Options
-v, –verbose               increase verbosity
-q, –quiet                 suppress non-error messages
–no-motd               suppress daemon-mode MOTD (see manpage caveat)
-c, –checksum              skip based on checksum, not mod-time & size
-a, –archive               archive mode; equals -rlptgoD (no -H,-A,-X)
–no-OPTION             turn off an implied OPTION (e.g. –no-D)
-r, –recursive             recurse into directories
-R, –relative              use relative path names
–no-implied-dirs       don’t send implied dirs with –relative
-b, –backup                make backups (see –suffix & –backup-dir)
–backup-dir=DIR        make backups into hierarchy based in DIR
–suffix=SUFFIX         set backup suffix (default ~ w/o –backup-dir)
-u, –update                skip files that are newer on the receiver
–inplace               update destination files in-place (SEE MAN PAGE)
–append                append data onto shorter files
–append-verify         like –append, but with old data in file checksum
-d, –dirs                  transfer directories without recursing
-l, –links                 copy symlinks as symlinks
-L, –copy-links            transform symlink into referent file/dir
–copy-unsafe-links     only “unsafe” symlinks are transformed
–safe-links            ignore symlinks that point outside the source tree
-k, –copy-dirlinks         transform symlink to a dir into referent dir
-K, –keep-dirlinks         treat symlinked dir on receiver as dir
-H, –hard-links            preserve hard links
-p, –perms                 preserve permissions
-E, –executability         preserve the file’s executability
–chmod=CHMOD           affect file and/or directory permissions
-A, –acls                  preserve ACLs (implies –perms)
-X, –xattrs                preserve extended attributes
-o, –owner                 preserve owner (super-user only)
-g, –group                 preserve group
–devices               preserve device files (super-user only)
–specials              preserve special files
-D                          same as –devices –specials
-t, –times                 preserve modification times
-O, –omit-dir-times        omit directories from –times
–super                 receiver attempts super-user activities
–fake-super            store/recover privileged attrs using xattrs
-S, –sparse                handle sparse files efficiently
-n, –dry-run               perform a trial run with no changes made
-W, –whole-file            copy files whole (without delta-xfer algorithm)
-x, –one-file-system       don’t cross filesystem boundaries
-B, –block-size=SIZE       force a fixed checksum block-size
-e, –rsh=COMMAND           specify the remote shell to use
–rsync-path=PROGRAM    specify the rsync to run on the remote machine
–existing              skip creating new files on receiver
–ignore-existing       skip updating files that already exist on receiver
–remove-source-files   sender removes synchronized files (non-dirs)
–del                   an alias for –delete-during
–delete                delete extraneous files from destination dirs
–delete-before         receiver deletes before transfer, not during
–delete-during         receiver deletes during transfer (default)
–delete-delay          find deletions during, delete after
–delete-after          receiver deletes after transfer, not during
–delete-excluded       also delete excluded files from destination dirs
–ignore-errors         delete even if there are I/O errors
–force                 force deletion of directories even if not empty
–max-delete=NUM        don’t delete more than NUM files
–max-size=SIZE         don’t transfer any file larger than SIZE
–min-size=SIZE         don’t transfer any file smaller than SIZE
–partial               keep partially transferred files
–partial-dir=DIR       put a partially transferred file into DIR
–delay-updates         put all updated files into place at transfer’s end
-m, –prune-empty-dirs      prune empty directory chains from the file-list
–numeric-ids           don’t map uid/gid values by user/group name
–timeout=SECONDS       set I/O timeout in seconds
–contimeout=SECONDS    set daemon connection timeout in seconds
-I, –ignore-times          don’t skip files that match in size and mod-time
–size-only             skip files that match in size
–modify-window=NUM     compare mod-times with reduced accuracy
-T, –temp-dir=DIR          create temporary files in directory DIR
-y, –fuzzy                 find similar file for basis if no dest file
–compare-dest=DIR      also compare destination files relative to DIR
–copy-dest=DIR         … and include copies of unchanged files
–link-dest=DIR         hardlink to files in DIR when unchanged
-z, –compress              compress file data during the transfer
–compress-level=NUM    explicitly set compression level
–skip-compress=LIST    skip compressing files with a suffix in LIST
-C, –cvs-exclude           auto-ignore files the same way CVS does
-f, –filter=RULE           add a file-filtering RULE
-F                          same as –filter=’dir-merge /.rsync-filter’
repeated: –filter=’- .rsync-filter’
–exclude=PATTERN       exclude files matching PATTERN
–exclude-from=FILE     read exclude patterns from FILE
–include=PATTERN       don’t exclude files matching PATTERN
–include-from=FILE     read include patterns from FILE
–files-from=FILE       read list of source-file names from FILE
-0, –from0                 all *-from/filter files are delimited by 0s
-s, –protect-args          no space-splitting; only wildcard special-chars
–address=ADDRESS       bind address for outgoing socket to daemon
–port=PORT             specify double-colon alternate port number
–sockopts=OPTIONS      specify custom TCP options
–blocking-io           use blocking I/O for the remote shell
–stats                 give some file-transfer stats
-8, –8-bit-output          leave high-bit chars unescaped in output
-h, –human-readable        output numbers in a human-readable format
–progress              show progress during transfer
-P                          same as –partial –progress
-i, –itemize-changes       output a change-summary for all updates
–out-format=FORMAT     output updates using the specified FORMAT
–log-file=FILE         log what we’re doing to the specified FILE
–log-file-format=FMT   log updates using the specified FMT
–password-file=FILE    read daemon-access password from FILE
–list-only             list the files instead of copying them
–bwlimit=KBPS          limit I/O bandwidth; KBytes per second
–write-batch=FILE      write a batched update to FILE
–only-write-batch=FILE like –write-batch but w/o updating destination
–read-batch=FILE       read a batched update from FILE
–protocol=NUM          force an older protocol version to be used
–iconv=CONVERT_SPEC    request charset conversion of filenames
-4, –ipv4                  prefer IPv4
-6, –ipv6                  prefer IPv6
–version               print version number
(-h) –help                  show this help (-h works with no other options)