3 .\" Author: Jean-Louis Martineau <martineau@zmanda.com>
4 .\" Generator: DocBook XSL Stylesheets vsnapshot_8273 <http://docbook.sf.net/>
6 .\" Manual: Miscellanea
7 .\" Source: Amanda 2.6.1p2
10 .TH "AMANDA\-AUTH" "7" "11/05/2009" "Amanda 2\&.6\&.1p2" "Miscellanea"
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12 .\" * set default formatting
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14 .\" disable hyphenation
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19 .\" * MAIN CONTENT STARTS HERE *
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22 amanda-auth \- Communication/Authentication methods between \fIAmanda\fR server and client
26 offers 7 methods of communication between Amanda server (sometimes also called the tape server) and clients, each with its own authentication method\&. The desired communication method is specified by the
28 parameter in the amanda\&.conf file (\fBamanda.conf\fR(5)) commonly as a dumptype\&. Valid values to the
38 \fBssh\fR\&. Please note that
40 will be removed in the next release\&. The authentication and communication method is used during the backup process
42 (amdump(8)) as well as the recovery process
44 (amrecover(8))\&. For detailed information, please see http://wiki\&.zmanda\&.com/index\&.php/Server/Client_authentication\&.
45 .SH "COMPILATION AND GENERAL INFORMATION"
47 The communication method and thus type of authentication that will be used by the Amanda server is specified by the
49 parameter in the dumptype for each disklist entry (DLE)\&. The
51 parameter thus may be easily and globally specified in the "global" dumptype\&. If
55 communication method is used\&. See
57 for more information on Amanda configuration and dumptypes, and
59 for more information on disklists\&.
61 On the client side, the Amanda daemon
63 validates the connection depending on the value of the
65 argument passed to it (see
66 \fIAmanda\fR(8))\&. Also, when it comes to recovery, the
68 parameter can be specified in the
69 \fBamanda-client.conf\fR(5)
70 file to specify the communication method to be used by the client to the server\&.
74 is being built from source code, desired communication and thus authentication methods (shown as "Authentication") must be specified as configure options at compilation time\&.
77 Authentication Configure option(s)
78 bsd \-\-with\-bsd\-security \-\-with\-amandahosts (pre\-2\&.6)
79 bsdtcp \-\-with\-bsdtcp\-security \-\-with\-amandahosts (pre\-2\&.6)
80 bsdudp \-\-with\-bsdudp\-security \-\-with\-amandahosts (pre\-2\&.6)
81 krb5 \-\-with\-krb5\-security
82 local (always included)
83 rsh \-\-with\-rsh\-security
84 ssh \-\-with\-ssh\-security
87 There are additional configure options for
91 to allow for specifying explicit UDP and TCP port ranges\&.
94 \-\-with\-udpportrange
95 \-\-with\-tcpportrange
96 \-\-with\-low\-tcpportrange
101 below for more information\&.
103 There are additional configure options for Kerberos if you so desire\&. All but the last option are for Kerberos 4\&. Defaults shown in square brackets\&.
106 \-\-with\-server\-principal=ARG server host principal [amanda]
107 \-\-with\-server\-instance=ARG server host instance []
108 \-\-with\-server\-keyfile=ARG server host key file [/\&.amanda]
109 \-\-with\-client\-principal=ARG client host principal [rcmd]
110 \-\-with\-client\-instance=ARG client host instance [HOSTNAME_INSTANCE]
111 \-\-with\-client\-keyfile=ARG client host key file [KEYFILE]
112 \-\-with\-ticket\-lifetime=ARG ticket lifetime [128]
113 \-\-with\-krb4\-security=DIR where libkrb\&.a lives [see below]
114 \-\-with\-krb5\-security=DIR where libkrb\&.a lives [see below]
117 If configuring with \-\-with\-krb4\-security and/or \-\-with\-krb5\-security, the configure script will search under /usr/kerberos/lib, /usr/cygnus/lib, /usr/lib, and /opt/kerberos/lib for the kerberos bits, libkrb\&.a, in this order\&. Kerberos support will not be added if it does not find them\&. If the kerberos bits are found under some other hierarchy, you can specify this via \-\-with\-krb5\-security=DIR and/or \-\-with\-krb4\-security=DIR, where DIR is where the kerberos bits live\&. The configure script will then look in the \'lib\' directory under this hierarchy for libkrb\&.a\&.
121 parameter selects a communication/authentication method to use between the client and the backup server\&. These methods are described each in their own section below\&.
122 .SH "BSD, BSDUDP, AND BSDTCP COMMUNICATION AND AUTHENTICATION"
124 For more detail, see http://wiki\&.zmanda\&.com/index\&.php/Configuring_bsd/bsdudp/bsdtcp_authentication\&.
130 communication methods use either UDP, TCP, or both protocols operating as a network service to authenticate and exchange data between server and clients\&.
132 In addition to compilation and general configuration (see
133 \fBCOMPILATION AND GENERAL INFORMATION\fR
134 above), the authentication method that the client is configured to receive is specified by the
136 parameter in the network service configuration for
137 \fIAmanda\fR\&. The authentication method used by an Amanda client to reach the server during recovery is the authentication method specified by the
139 parameter in the client\'s Amanda network service configuration or in its amanda\-client\&.conf file (see amanda\-client\&.conf(5))\&.
140 .SS "\&.amandahosts file"
142 Servers and clients using the bsd, bsdudp, and bsdtcp authentication methods refer to the \&.amandahosts file to control access\&. Amanda should be compiled for this access control if one of these methods will be used and is the default compilation option for Amanda 2\&.6 (use \-\-with\-amandahosts when compiling pre\-2\&.6 versions of Amanda)\&.
144 Amanda looks for the \&.amandahosts file in the Amanda user\'s home directory, commonly /var/lib/amanda\&.
146 Each authorization is on its own line in the following format
152 \fIservice\&.\&.\&.\fR
157 is ommitted, it defaults to the user running
158 \fBamandad\fR, i\&.e\&. the user listed in the
162 configuration file\&.
164 \fIservice\&.\&.\&.\fR
165 is a space\-delimited list of services the client is authorized to execute:
171 (a shortcut for the previous four services which are required on clients),
173 \fBamidxtaped\fR\&. The last two services are required on a server for clients to connect to it using
176 Example of the \&.amandahosts file on an Amanda client
179 \fBamandaserver\&.example\&.com amandabackup amdump\fR
182 Example of the \&.amandahosts file on an Amanda server
185 \fBamandaclient1\&.example\&.com root amindexd amidxtaped\fR
187 .SS "bsd communication and authentication"
189 The authentication is done using \&.amandahosts file in the Amanda user\'s home directory\&. The protocol between Amanda server and client is UDP\&. The number of disk list entries (DLEs)\-\-number of Amanda clients\-\-is limited by the UDP packet size\&. This authentication protocol will use a different port for each data stream (see PORT USAGE below)
190 .SS "bsdudp communication and authentication"
192 The authentication is done using \&.amandahosts files in the Amanda user\'s home directory\&. It uses UDP protocol between Amanda server and client for data and hence the number of DLEs is limited by the UDP packet size\&. It uses one TCP port to establish the connection and multiplexes all data streams using one port on the server (see PORT USAGE below)\&.
193 .SS "bsdtcp communication and authentication"
195 The authentication is done using \&.amandahosts files in the backup user\'s (for example: amandabackup) home directory\&. It uses TCP protocol between Amanda server and client\&. On the client, two reserved ports are used\&. On the server, all data streams are multiplexed to one port (see PORT USAGE below)\&.
196 .SS "USING INETD SERVER"
198 Template for Amanda client inetd service entry
201 \fI service_name\fR \fIsocket_type\fR \fIprotocol\fR \fIwait/nowait\fR \fIamanda_backup_user\fR \fIabsolute_path_to_amandad\fR amandad \fIserver_args\fR
204 Client example of using
206 authorization for inetd server given Amanda user is "amandabackup":
209 \fB amanda dgram udp wait amandabackup /path/to/amandad amandad \-auth=bsd amdump\fR
212 The same could be used for
214 if specifying \-auth=bsdudp instead of \-auth=bsd\&.
216 Client example of using
218 authorization for inetd server given Amanda user is "amandabackup":
221 \fB amanda stream tcp nowait amanda /path/to/amandad amandad \-auth=bsdtcp amdump\fR
227 would typically be added at the end of the line as
229 server arguments for an Amanda server\&.
231 Server example of using
233 authorization for inetd server given Amanda user is "amandabackup":
236 \fB amanda stream tcp nowait amanda /path/to/amandad amandad \-auth=bsdtcp amdump amindexd amidxtaped\fR
239 For Amanda version 2\&.5\&.0 and earlier, remember that neither
243 are supported and the Amanda daemon
245 accepts no arguments\&. Because of the latter,
247 as of Amanda version 2\&.5\&.1 is not compatible with 2\&.5\&.0 and earlier servers\&. Thus, servers that are 2\&.5\&.0 or earlier must, in addition to the
253 Amanda services as their own network services, amandaidx and amidxtape, respectively (see below)\&.
255 There are no compatibility issues if server and clients are all 2\&.5\&.0 or earlier\&. If your server is 2\&.5\&.1 or later, you can still have clients that are 2\&.5\&.0 and earlier although you must then use
257 communication/authentication with these clients and must also run
261 Amanda services on the server as their own network services, amandaidx and amidxtape, respectively (see below)\&. If you have a server that is 2\&.5\&.0 and earlier, clients of a later version on which you wish to run
265 instead and, again, the server must be running the amandaidx and amidxtape network services\&.
267 Example of amindexd and amidxtaped Amanda daemon services configured as their own network services for a 2\&.5\&.0 or earlier server or a newer server having 2\&.5\&.0 or earlier clients
270 \fB amandaidx stream tcp nowait amanda /usr/local/libexec/amanda/current/amindexd amindexd\fR
271 \fB amidxtape stream tcp nowait amanda /usr/local/libexec/amanda/current/amidxtaped amidxtaped\fR
273 .SS "USING XINETD SERVER"
275 Template for Amanda client xinetd service file
280 only_from = \fIAmanda server\fR
281 socket_type = \fIsocket type\fR
282 protocol = \fIprotocol\fR
284 user = \fIamanda backup user\fR
285 group = \fIamanda backup user group id\fR
287 server = \fIabsolute path to amandad\fR
288 server_args = \fIamandad server arguments\fR
295 parameter can be used with xinetd but is usually in addition to the primary form of access control via the \&.amandahosts file\&.
297 Client example of using
299 authorization for xinetd server and for Amanda user "amandabackup":
304 only_from = amandaserver\&.example\&.com
311 server = /path/to/amandad
312 server_args = \-auth=bsd amdump
317 The same could be used for
319 if specifying \-auth=bsdudp instead of \-auth=bsd\&.
321 Client example of using
323 authorization for xinetd server and for Amanda user "amandabackup":
328 only_from = amandaserver\&.example\&.com amandaclient\&.example\&.com
335 server = /path/to/amandad
336 server_args = \-auth=bsdtcp amdump
344 would typically be added as additional
347 for an Amanda server\&.
349 For Amanda version 2\&.5\&.0 and earlier, remember that neither
353 are supported and the Amanda daemon
355 accepts no arguments\&. Because of the latter,
357 as of Amanda version 2\&.5\&.1 is not compatible with 2\&.5\&.0 and earlier servers\&. Thus, servers that are 2\&.5\&.0 or earlier must, in addition to the
363 Amanda services as their own network services, amandaidx and amidxtape, respectively (see below)\&.
365 There are no compatibility issues if server and clients are all 2\&.5\&.0 or earlier\&. If your server is 2\&.5\&.1 or later, you can still have clients that are 2\&.5\&.0 and earlier although you must then use
367 communication/authentication with these clients and must also run
371 Amanda services on the server as their own network services, amandaidx and amidxtape, respectively (see below)\&. If you have a server that is 2\&.5\&.0 and earlier, clients of a later version on which you wish to run
375 instead and, again, the server must be running the amandaidx and amidxtape network services\&.
377 Example of amindexd and amidxtaped Amanda daemon services configured as their own network services for a 2\&.5\&.0 or earlier server or a newer server having 2\&.5\&.0 or earlier clients
387 server = /usr/local/libexec/amanda/amindexd
398 server = /usr/local/libexec/amanda/amidxtaped
404 List of TCP/UDP ports used by network service communication methods for Amanda server and client\&.
409 RPpAP = Reserved Port per Amanda Process
410 UPpDLE = Unreserved Port per DLE
411 [\&.\&.] = Configure options that can be used at compile time to define port ranges
413 Authentication Protocol Amanda server Amanda client
414 bsd udp 1 RPpAP [\-\-with\-udpportrange] 10080
415 tcp 1 UP [\-\-with\-tcpportrange] 3 UPpDLE [\-\-with\-tcpportrange]
416 bsdudp udp 1 RPpAP [\-\-with\-udpportrange] 10080
417 tcp 1 UP [\-with\-tcpportrange] 1 UPpDLE [\-\-with\-tcpportrange]
418 bsdtcp tcp 1 RPpAP [\-\-with\-low\-tcpportrange] 10080
421 Amanda server also uses two ports (dumper process) to communicate with the chunker/taper processes\&. These ports are in the range set by \-\-with\-tcpportrange\&.
423 You can override the default port ranges that Amanda was compiled with in each configuration using the
424 \fIreserved\-udp\-port\fR,
425 \fIreserved\-tcp\-port\fR, and
426 \fIunreserved\-tcp\-port\fR
427 parameters in amanda\&.conf and amanda\-client\&.conf configuration files (see
430 \fBamanda-client.conf\fR(5))\&.
431 .SH "KERBEROS COMMUNICATION AND AUTHENTICATION"
433 For more detail, see http://wiki\&.zmanda\&.com/index\&.php/Kerberos_authentication\&.
435 Amanda supports Kerberos 4 and 5 communication methods between Amanda server and client\&. Please note, however, that support for Kerberos 4 will be removed in the next release\&.
437 General information including compilation are given above (see
438 \fBCOMPILATION AND GENERAL INFORMATION\fR
439 above)\&. Below sections give specific Kerberos 4 and 5 information\&.
442 Please note that support for Kerberos 4 will be removed in the next release\&.
444 Kerberos 4 uses UDP protocol and the number of DLEs is limited by UDP packet size\&.
446 The kerberized AMANDA service uses a different port on the client hosts\&. The /etc/services line is:
450 And the /etc/inetd\&.conf line is:
453 kamanda dgram udp wait root /usr/local/libexec/amanda/amandad amandad \-auth=krb4
456 Note that you\'re running this as root, rather than as your dump user\&. AMANDA will set its uid down to the dump user at times it doesn\'t need to read the srvtab file, and give up root permissions entirely before it goes off and runs dump\&. Alternately you can change your srvtab files to be readable by user amanda\&.
458 The following dumptype options apply to krb4:
461 auth "krb4" # use krb4 auth for this host
462 # (you can mingle krb hosts and bsd \&.rhosts in one conf)
463 kencrypt # encrypt this filesystem over the net using the krb4
464 # session key\&. About 2x slower\&. Good for those root
465 # partitions containing your keyfiles\&. Don\'t want to
466 # give away the keys to an ethernet sniffer!
467 # This is currently always enabled\&. There is no
468 # way to disable it\&. This is a bug\&.
472 Kerberos 5 uses TCP and the server uses only one TCP port and data streams are multiplexed to this port\&.
475 The \fBkrb5\fR driver script defaults to:
478 * The lifetime of our tickets in minutes\&.
480 #define AMANDA_TKT_LIFETIME (12*60)
483 * The name of the service in /etc/services\&.
485 #define AMANDA_KRB5_SERVICE_NAME "k5amanda"
487 You can currently only override these by editing the source code\&.
489 The kerberized AMANDA service uses a different port on the client hosts\&. The /etc/services line is:
493 And the /etc/inetd\&.conf line is:
496 k5amanda stream tcp nowait root /usr/local/libexec/amanda/amandad amandad \-auth=krb5
499 Note that you\'re running this as root, rather than as your dump user\&. AMANDA will set its UID down to the dump user at times it doesn\'t need to read the keytab file, and give up root permissions entirely before it goes off and runs dump\&. Alternately you can change your keytab files to be readable by user amanda\&. You should understand the security implications of this before changing the permissions on the keytab\&.
501 The following dumptype options apply to
505 auth "krb5" # use krb5 auth for this host
506 # (you can mingle krb hosts and bsd \&.rhosts in one conf)
509 The principal and keytab files that Amanda uses must be set in the amanda\&.conf file for kerberos 5 dumps to work\&. You can hardcode this in the source code if you really want to (common\-src/krb5\-security\&.c)
519 krb5keytab "/etc/krb5\&.keytab\-amanda"
520 krb5principal "amanda/saidin\&.omniscient\&.com"
523 The principal in the second option must be contained in the first\&. The keytab should be readable by the amanda user (and definitely not world readable!) and is (obviously) on the server\&. In MIT\'s kadmin, the following:
526 addprinc \-randkey amanda/saidin\&.omniscient\&.com
527 ktadd \-k /etc/krb5\&.keytab\-amanda amanda/saidin\&.omniscient\&.com
530 will do the trick\&. You will obviously want to change the principal name to reflect something appropriate for the conventions at your site\&.
532 You must also configure each client to allow the amanda principal in for dumps\&.
534 There are several ways to go about authorizing a server to connect to a client\&.
536 The normal way is via a \&.k5amandausers file or a \&.k5login file in the client user\'s home directory\&. The determination of which file to use is based on the way you ran configure on AMANDA\&. By default, AMANDA will use \&.k5amandahosts, but if you configured with \-\-without\-amandahosts, AMANDA will use \&.k5login\&. (similar to the default for \&.rhosts/\&.amandahosts\-style security)\&. The \&.k5login file syntax is a superset of the default
538 \&.k5login\&. The routines to check it are implemented in amanda rather than using krb5_kuserok because the connections are actually gssapi based\&.
540 This \&.k5amandahosts/\&.k5login is a hybrid of the \&.amandahosts and a \&.k5login file\&. You can just list principal names, as in a \&.k5login file and the principal will be permitted in from any host\&. If you do NOT specify a realm, then there is no attempt to validate the realm (this is only really a concern if you have cross\-realm authentication set up with another realm or something else that allows you multiple realms in your kdc\&. If you do specify a realm, only that principal@realm will be permitted to connect\&.
542 You may prepend this with a hostname and whitespace, and only that principal (with optional realm as above) will be permitted to access from that hostname\&.
544 Here are examples of valid entries in the \&.k5amandahosts:
548 service/amanda@TEST\&.COM
549 dumpmaster\&.test\&.com service/amanda
550 dumpmaster\&.test\&.com service/amanda@TEST\&.COM
553 Rather than using a \&.k5amandahosts or \&.k5login file, the easiest way is to use a principal named after the destination user, (such as amanda@TEST\&.COM in our example) and not have either a \&.k5amandahosts or \&.k5login file in the destination user\'s home directory\&.
555 There is no attempt to verify the realm in this case (only a concern if you have cross\-realm authentication setup)\&.
556 .SH "LOCAL COMMUNICATION"
558 The Amanda server communicates with the client internally versus over the network, ie\&. the client is also the server\&.
560 This is the only method that requires no authentication as it is clearly not needed\&.
561 .SH "RSH COMMUNICATION AND AUTHENTICATION"
563 For more detail, see http://wiki\&.zmanda\&.com/index\&.php/Configuring_rsh_authentication\&.
565 The Amanda server communicates with its client as the Amanda user via the RSH protocol\&.
567 Please note that RSH protocol itself is insecure and should be used with caution especially on any servers and clients with public IPs\&.
569 Each Amanda client communicates with the server using one TCP port and all data streams from the client are multiplexed over one port\&. The number of Amanda clients is limited by the number of reserved ports available on the Amanda server\&. Some versions of RSH do not use reserved ports and, thus, this restriction is not valid\&.
571 General information including compilation is given above (see
572 \fBCOMPILATION AND GENERAL INFORMATION\fR
575 In addition to specifying the
577 field in dumptype definition, it might be required to specify
578 \fIclient_username\fR
581 fields\&. If the backup user name is different on the Amanda client, the user name is specified as
582 \fBclient_username\fR\&. If the location of the Amanda daemon
584 is different on the Amanda client, the location is specified as
590 define dumptype rsh_example {
593 client_username "amandabackup"
594 amandad_path "/usr/lib/exec/amandad"
598 .SH "SSH COMMUNICATION AND AUTHENTICATION"
600 For more detail, see http://wiki\&.zmanda\&.com/index\&.php/How_To:Set_up_transport_encryption_with_SSH\&.
602 Amanda client sends data to the server using SSH\&. SSH keys have to be set up so that Amanda server can communicate with its clients using SSH\&.
604 General information including compilation is given above (see \fBCOMPILATION AND GENERAL INFORMATION\fR above)\&.
606 SSH provides transport encryption and authentication\&. To set up an SSH authentication session, Amanda will run the equivalent of the following to start the backup process\&.
608 \fB /path/to/ssh \-l \fR\fB\fIuser_name\fR\fR\fB client\&.zmanda\&.com $libexecdir/amandad\fR
610 To use SSH, you need to set up SSH keys either by storing the passphrase in cleartext, using ssh\-agent, or using no passphrase at all\&. All of these options have security implications which should be carefully considered before adoption\&.
612 When you use a public key on the client to do data encryption (see http://wiki\&.zmanda\&.com/index\&.php/How_To:Set_up_data_encryption), you can lock away the private key in a secure place\&. Both, transport and storage will be encrypted with such a setup\&. See http://wiki\&.zmanda\&.com/index\&.php/Encryption for an overview of encryption options\&.
614 Enable SSH authentication and set the ssh_keys option in all DLEs for that host by adding the following to the DLE itself or to the corresponding dumptype in amanda\&.conf:
617 ssh_keys "/home/amandabackup/\&.ssh/id_rsa_amdump"
619 \fIssh_keys\fR is the path to the private key on the client\&. If the username to which Amanda should connect is different from the default, then you should also add
621 client_username "otherusername"
623 If your server \fBamandad\fR path and client \fBamandad\fR path are different, you should also add
625 amandad_path "/client/amandad/path"
627 For a marginal increase in security, prepend the keys used for AMANDA in the clients\' authorized_keys file with the following:
630 from="amanda_server\&.your\&.domain\&.com",no\-port\-forwarding,no\-X11\-forwarding,no\-agent\-forwarding,command="/absolute/path/to/amandad \-auth=ssh amdump"
633 This will limit that key to connect only from Amanda server and only be able to execute
636 In the same way, prepend the key used for AMANDA in the server\'s authorized_keys file with:
639 from="amanda_client\&.your\&.domain\&.com",no\-port\-forwarding,no\-X11\-forwarding,no\-agent\-forwarding,command="/absolute/path/to/amandad \-auth=ssh amindexd amidxtaped"
642 You can omit the from=\&.\&. option if you have too many clients to list, although this has obvious security implications\&.
644 Set ssh_keys and any other necessary options in /etc/amanda/amanda_client\&.conf:
648 ssh_keys "/root/\&.ssh/id_rsa_amrecover"
649 client_username "amanda"
650 amandad_path "/server/amandad/path"
653 Besides user keys, SSH uses host keys to uniquely identify each host, to prevent one host from impersonating another\&. Unfortunately, the only easy way to set up these host keys is to make a connection and tell SSH that you trust the identity:
656 $ ssh client1\&.zmanda\&.com
657 The authenticity of host \'client1\&.zmanda\&.com (192\&.168\&.10\&.1)\' can\'t be established\&.
658 RSA key fingerprint is 26:4e:df:a2:be:c8:cb:20:1c:68:8b:cc:c0:3b:8e:9d\&.
659 Are you sure you want to continue connecting (yes/no)?yes
662 As Amanda will not answer this question itself, you must manually make every connection (server to client and client to server) that you expect Amanda to make\&. Note that you must use the same username that Amanda will use (that is, ssh client and ssh client\&.domain\&.com are distinct)\&.
666 \fBamanda.conf\fR(5),
667 \fBamanda-client.conf\fR(5),
671 : http://wiki.zmanda.com
674 \fBJean\-Louis Martineau\fR <\&martineau@zmanda\&.com\&>
676 Zmanda, Inc\&. (http://www\&.zmanda\&.com)
679 \fBDustin J\&. Mitchell\fR <\&dustin@zmanda\&.com\&>
681 Zmanda, Inc\&. (http://www\&.zmanda\&.com)
684 \fBPaul Yeatman\fR <\&pyeatman@zmanda\&.com\&>
686 Zmanda, Inc\&. (http://www\&.zmanda\&.com)
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