1VFS_FILEID(8)             System Administration tools            VFS_FILEID(8)
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NAME

6       vfs_fileid - Generates file_id structs with unique device id values for
7       cluster setups
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SYNOPSIS

10       vfs objects = fileid
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DESCRIPTION

13       This VFS module is part of the samba(7) suite.
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15       Samba uses file_id structs to uniquely identify files for locking
16       purpose. By default the file_id contains the device and inode number
17       returned by the stat() system call. As the file_id is a unique
18       identifier of a file, it must be the same on all nodes in a cluster
19       setup. This module overloads the SMB_VFS_FILE_ID_CREATE() operation and
20       generates the device number based on the configured algorithm (see the
21       "fileid:algorithm" option).
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23       When using the fsname or fsid algorithm a stat() and statfs() call is
24       required for all mounted file systems to generate the file_id. If e.g.
25       an NFS file system is unresponsive such a call might block and the smbd
26       process will become unresponsive. Use the "fileid:fstype deny",
27       "fileid:fstype allow", "fileid:mntdir deny", or "fileid:mntdir allow"
28       options to ignore potentially unresponsive file systems.
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OPTIONS

31       fileid:algorithm = ALGORITHM
32           Available algorithms are fsname, fsname_nodirs, fsid and hostname.
33           The default value is fsname.
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35           The fsname algorithm generates device id by hashing the kernel
36           device name.
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38           The fsname_nodirs algorithm generates device id by hashing the
39           kernel device name for files and by hashing the hostname for
40           directories. This can be used to deliberately break lock coherency
41           for directories in a cluster.
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43           The fsid algorithm generates the device id from the f_fsid returned
44           from the statfs() syscall.
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46           The hostname algorithm generates device id by hashing the hostname.
47           This can be used to deliberately break lock coherency in a cluster.
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49           The fsname_norootdir algorithm generates device ids by hashing the
50           kernel device name, except for the root directory of shares where
51           it will use the hostname algorithm. This can be used to
52           deliberately break lock coherency in a cluster for the root
53           directory of a share.
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55       fileid:mapping = ALGORITHM
56           This option is the legacy version of the fileid:algorithm option,
57           which was used in earlier versions of fileid mapping feature in
58           custom Samba 3.0 versions.
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60       fileid:fstype deny = LIST
61           List of file system types to be ignored for file_id generation.
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63       fileid:fstype allow = LIST
64           List of file system types to be allowed for file_id generation. If
65           this option is set, file system types not listed here are ignored.
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67       fileid:mntdir deny = LIST
68           List of file system mount points to be ignored for file_id
69           generation.
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71       fileid:mntdir allow = LIST
72           List of file system mount points to be allowed for file_id
73           generation. If this option is set, file system mount points not
74           listed here are ignored.
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76       fileid:nolockinode
77           This option triggers use of the fileid hostname algorithm for the
78           configured inode which can be used to deliberately break lock
79           coherency for the corresponding file or directory in a cluster.
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EXAMPLES

82       Usage of the fileid module with the fsid algorithm:
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84                   [global]
85                vfs objects = fileid
86                fileid:algorithm = fsid
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VERSION

89       This man page is part of version 4.9.8 of the Samba suite.
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AUTHOR

92       The original Samba software and related utilities were created by
93       Andrew Tridgell. Samba is now developed by the Samba Team as an Open
94       Source project similar to the way the Linux kernel is developed.
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98Samba 4.9.8                       05/14/2019                     VFS_FILEID(8)
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