+=head2 How BackupPC Finds Hosts
+
+Starting with v2.0.0 the way hosts are discovered has changed. In most
+cases you should specify 0 for the DHCP flag in the conf/hosts file,
+even if the host has a dynamically assigned IP address.
+
+BackupPC (starting with v2.0.0) looks up hosts with DHCP = 0 in this manner:
+
+=over 4
+
+=item *
+
+First DNS is used to lookup the IP address given the client's name
+using perl's gethostbyname() function. This should succeed for machines
+that have fixed IP addresses that are known via DNS. You can manually
+see whether a given host have a DNS entry according to perls'
+gethostbyname function with this command:
+
+ perl -e 'print(gethostbyname("myhost") ? "ok\n" : "not found\n");'
+
+=item *
+
+If gethostbyname() fails, BackupPC then attempts a NetBios multicast to
+find the host. Provided your client machine is configured properly,
+it should respond to this NetBios multicast request. Specifically,
+BackupPC runs a command of this form:
+
+ nmblookup myhost
+
+If this fails you will see output like:
+
+ querying myhost on 10.10.255.255
+ name_query failed to find name myhost
+
+If this success you will see output like:
+
+ querying myhost on 10.10.255.255
+ 10.10.1.73 myhost<00>
+
+Depending on your netmask you might need to specify the -B option to
+nmblookup. For example:
+
+ nmblookup -B 10.10.1.255 myhost
+
+If necessary, experiment on the nmblookup command that will return the
+IP address of the client given its name. Then update
+$Conf{NmbLookupFindHostCmd} with any necessary options to nmblookup.
+
+=back
+
+For hosts that have the DHCP flag set to 1, these machines are
+discovered as follows:
+
+=over 4
+
+=item *
+
+A DHCP address pool ($Conf{DHCPAddressRanges}) needs to be specified.
+BackupPC will check the NetBIOS name of each machine in the range using
+a command of the form:
+
+ nmblookup -A W.X.Y.Z
+
+where W.X.Y.Z is each candidate address from $Conf{DHCPAddressRanges}.
+Any host that has a valid NetBIOS name returned by this command (ie:
+matching an entry in the hosts file) will be backed up. You can
+modify the specific nmblookup command if necessary via $Conf{NmbLookupCmd}.
+
+=item *
+
+You only need to use this DHCP feature if your client machine doesn't
+respond to the NetBios multicast request:
+
+ nmblookup myHost
+
+but does respond to a request directed to its IP address:
+
+ nmblookup -A W.X.Y.Z
+
+=back
+
projects / BackupPC.git / blobdiff