When first written, this article was about copying a physical hardware system. Nowadays, few systems are physical, and "cloud" is pervasive. Read about [[Cloning/Droplet]] for an updated version.
Once you have [[backups]], you can and should test the ability to restore those backups to a new hardware environment. The restore procedure is going to depend on what you used to create your "image" in the first place. Independent of the notion of backups, a system administrator (or even an experienced user) will want to "clone" a computer system. That is make an identical copy or nearly identical copy of a computer on different hardware. The most widespread use-case for this is when a person gets a new computer and wants to migrate the old computer software and data to the new hardware. From the system administrator's perspective, the common use case is different: it's when you have to build out a cluster, provide redundancy, or otherwise scale a hardware/software platform.
Consider all the times that you could produce a system that you wish to replicate. For example, a standard "Developer's Workstation" or "Designer's Studio" or "Student Desktop" and many more technical varieties like "Web Front-end", "Mail Relay" etc.
While cloning is never a real-time operation, synchronization can be. For system architectures that require high availability, or scalability, you will need some form of [[synchronization]] for various components of the system (disk, databases, etc.) == Apt-get dpkg --set-selections ==
One way to do this on Debian-based systems (including Ubuntu) is to use <code>dpkg</code> get/set-selections in combination with <code>apt-get</code> using it's dselect-upgrade option:
the following:
=== on System A ===
<source lang="bash">
sudo dpkg --get-selections > package-list.txt
copy package-list.txt from System A to System B
=== on System B ===
<source lang="bash">
sudo dpkg --set-selections < package-list.txt
</source>
You might get 'database' errors, in which case you should install <code>dselect</code> and update that as well (all as root, or with sudo):
<source lang="bash">
apt-get update
apt-get install dselect
dselect update
apt-get -u dselect-upgrade
</source>
There are other tools to do the job too, and the tools you want to use for this depend on how automated you aim for this task to be, and how much you need/want to be able to customize each machine as it's being installed.
== KickStart ==
'''[http://fedoraproject.org/wiki/Anaconda/Kickstart Kickstart]''' is a Red Hat package that deploys Red Hat to multiple installation targets with minimal customisation. Aside from the wiki, it is also covered in [http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.3/html/Installation_Guide/index.html the Installation Guide for RedHat Enterprise Linux]
== System Imager ==
SystemImager is a third-party tool that does a better job. http://systemimager.org/
== Fully Automated Install ==
'''[http://www.informatik.uni-koeln.de/fai/ fai]''' (fully automated install) is a Debian-based tool to do likewise. Like System Imager, it's suitable for building clusters. See the
* [http://www.informatik.uni-koeln.de/fai/ project website] and the
* [http://faiwiki.informatik.uni-koeln.de/index.php/Main_Page wiki].
* [http://www.slideshare.net/henningsprang/automated-installations-and-infrastructure-management-with-fai-presentation presentation]
* [[:Media:Fai_poster_a4.pdf|Fully Automated Install (FAI) Poster]]
*[http://www.informatik.uni-koeln.de/fai/ project website] and the*[http://faiwiki.informatik.uni-koeln.de/index.php/Main_Page wiki].*[http://www.slideshare.net/henningsprang/automated-installations-and-infrastructure-management-with-fai-presentation presentation]*[[File:Fai_poster_a4.pdf|600px|thumb|right|Fully Automated Install (FAI) Poster]] == Replicator ==
'''Replicator''' seems like it could use some volunteers to expand. http://replicator.sourceforge.net/ It tries to do some customization for differences in hard disk sizes, video cards, etc. You may want to check it out.
== Partition Image == '''[http://www.partimage.org/ Partition Image]''' is a semi-automated tool for replicating a Linux partition to multiple targets. It is particularly useful as a system cloning tool, and has many uses for data backup and archiving of whole disks or partitions. ==Replicating a PHP installation==With the PHP CLI installed, you can use <code>php -m</code> to get a list of the compiled-in modules for your PHP installation. This is the same as you would find by using the <code>phpinfo();</code> function in a script, except that you get exactly the info you need, in a list format that you can use. That list can show you what you might need to install on another host to ensure that each host is compatible for the software you're running. However, it won't show you the name of the actual packages that you need to install. So, if you want to know what PHP packages are installed, you can do the following<source lang="bash"># On system A, get a list of the php packages that are installed## apt-based package manager: Debian, Ubuntudpkg --get-selections |grep -v deinstall | grep php5- | awk 'ORS=" " { print $1 }'## yum-based package manager: RedHat, CentOS, Fedora yum list installed | grep php5 | awk 'ORS=" " { print $1 }'# On system B, install those packagessudo apt-get install [LIST FROM A]</source>If system A and system B use different package managers, then the best you can do is get the list of the modules from each system and compare them. In our <code>diff</code>, we'll use the system we're moving from on the left, because <code>diff</code> is quirky and will show lines that 'differ' with a pipe symbol; thus it's less error-prone to print the first column with awk.<source lang="bash">A=webfaction.php.modules.txt B=digital.ocean.php.modules.txtdiff --suppress-common-lines --side-by-side $A $B </source>It's not perfect, but now we have a good list of the modules to search and install.<pre>>curl>gdgmpimapintlionCubeldapmailparsemcryptmemcachemysqlnd>pdo_pgsqlpdo_sqlitepgsqlpspell>sqlite3tidy>>>xmlrpcxslthe> </pre> See what's available on our new host. (repositories are different)<source lang="bash">apt-cache search php5-</source> <pre>php5-cgi - server-side, HTML-embedded scripting language (CGI binary)php5-cli - command-line interpreter for the php5 scripting languagephp5-common - Common files for packages built from the php5 sourcephp5-curl - CURL module for php5php5-dbg - Debug symbols for PHP5php5-dev - Files for PHP5 module developmentphp5-gd - GD module for php5php5-gmp - GMP module for php5php5-json - JSON module for php5php5-ldap - LDAP module for php5php5-mysql - MySQL module for php5php5-odbc - ODBC module for php5php5-pgsql - PostgreSQL module for php5php5-pspell - pspell module for php5php5-readline - Readline module for php5php5-recode - recode module for php5php5-snmp - SNMP module for php5php5-sqlite - SQLite module for php5php5-tidy - tidy module for php5php5-xmlrpc - XML-RPC module for php5php5-xsl - XSL module for php5libphp5-embed - HTML-embedded scripting language (Embedded SAPI library)php5-adodb - Extension optimising the ADOdb database abstraction libraryphp5-apcu - APC User Cache for PHP 5php5-enchant - Enchant module for php5php5-exactimage - fast image manipulation library (PHP bindings)php5-fpm - server-side, HTML-embedded scripting language (FPM-CGI binary)php5-gdcm - Grassroots DICOM PHP5 bindingsphp5-gearman - PHP wrapper to libgearmanphp5-geoip - GeoIP module for php5php5-gnupg - wrapper around the gpgme libraryphp5-imagick - ImageMagick module for php5php5-imap - IMAP module for php5php5-interbase - interbase/firebird module for php5php5-intl - internationalisation module for php5php5-lasso - Library for Liberty Alliance and SAML protocols - PHP 5 bindingsphp5-librdf - PHP5 language bindings for the Redland RDF libraryphp5-mapscript - php5-cgi module for MapServerphp5-mcrypt - MCrypt module for php5php5-memcache - memcache extension module for PHP5php5-memcached - memcached extension module for PHP5, uses libmemcachedphp5-midgard2 - Midgard2 Content Repository - PHP5 language bindings and modulephp5-ming - Ming module for php5php5-mongo - MongoDB database driverphp5-msgpack - PHP extension for interfacing with MessagePackphp5-mysqlnd - MySQL module for php5 (Native Driver)php5-mysqlnd-ms - MySQL replication and load balancing module for PHPphp5-oauth - OAuth 1.0 consumer and provider extensionphp5-pinba - Pinba module for PHP 5php5-ps - ps module for PHP 5php5-radius - PECL radius module for PHP 5php5-redis - PHP extension for interfacing with Redisphp5-remctl - PECL module for Kerberos-authenticated command executionphp5-rrd - PHP bindings to rrd tool systemphp5-sasl - Cyrus SASL Extensionphp5-stomp - Streaming Text Oriented Messaging Protocol (STOMP) client module for PHP 5php5-svn - PHP Bindings for the Subversion Revision control systemphp5-sybase - Sybase / MS SQL Server module for php5php5-tokyo-tyrant - PHP interface to Tokyo Cabinet's network interface, Tokyo Tyrantphp5-vtkgdcm - Grassroots DICOM VTK PHP bindingsphp5-xcache - Fast, stable PHP opcode cacherphp5-xdebug - Xdebug Module for PHP 5php5-xhprof - Hierarchical Profiler for PHP5</pre> And thus, our install<source lang="bash">sudo apt-get install php5-curl php5-gd php5-gmp php5-imap php5-intl php5-ldap php5-mcrypt php5-memcache php5-mysqlnd php5-pgsql php5-pspell php5-sqlite php5-tidy php5-xmlrpc php5-xsl</source>
[[Category:Howto]]