2 .\" (C) 2004, Pascal Schmidt
4 .TH tags 7 "04 Jan 2004"
6 tags \- tagged files used for clustering extensions
8 Tagged files are used by
12 to support NFS exporting directories like
16 to a cluster of client machines. The problem at hand is that different
17 files need to be served to different clients. Tagged files provide a
18 way to specify which file should be served to which client(s).
20 Tags are appended to the end of a filename and are seperated from the
21 rest of the name by beginning and ending with $$. For each file, there
22 can be multiple tagged variants. The normal file, without a tag, is
23 only served to clients by default when no tagged file matching the client is
24 found. The following tags exist:
27 If a client attempts to access this file, it will be redirected to the
28 normal file instead, no matter what other tagged files exist. This
29 is mainly useful for use inside symlinks that need to point to a normal
30 file although other access to the normal file should be redirected. In
31 this special case, the tagged file
33 does not even need to exist (the symlink will then seem to be dangling
37 If a client with an IP address of
39 attempts to access the normal file,
40 it will be redirected to this file instead.
42 .B file$$IP=a.b.c.d_n$$
43 If a client with an IP adress in the network
46 access the normal file, it will be redirected to this file instead. Note that
48 only supports 8, 16, and 24 as values for
52 If a client with the hostname
54 attempts to access the normal file, it will be redirected to this file instead.
57 If a client whose hostname begins with the string
59 attempts to access the normal file, it will be redirected to this file instead.
62 If any client attempts to access the normal file, it will be redirected to this
66 If any client attempts to access or create the normal file, it will be redirected to
70 is the IP address of the client. It does not matter whether the target
71 tagged file exists or not.
73 .B file$$ALWAYS=CLIENT$$
74 If any client attempts to access or create the normal file, it will be redirected to
76 instead. It does not matter whether that file exists or not.
79 Like above, but effective for all files in the directory where it is found.
82 Like above, but effective for all files in the directory where it is found.
84 Note that the ALWAYS tag can lead to file not found errors on clients
85 if the tagged files it redirects to does not exist on the server. For
88 can suffer from this problem. Furthermore, this tag is a
90 extension and does not exist in
92 When this tags exists, it prevents all access to the normal file by any
96 If any client attempts to create the normal file,
98 will be created instead, where
100 is the IP address of the client.
102 .B file$$CREATE=CLIENT$$
103 If any client attempts to create the normal file,
105 will be created instead.
108 Like above, but effective for all files in the directory where it is found.
111 Like above, but effective for all files in the directory where it is found.
113 Tags work for all kinds of named filesystem objects.
114 If multiple tagged files
115 are found for a normal file, they are considered in the order they are
116 given above, starting at the top. Processing stops once a match is found.
118 .BR ClusterNFS ", but not in " unfs3 ,
119 only files accessible and readable by a client are considered matches.