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           The fsname_norootdir_ext algorithm generates device ids by hashing
56           the kernel device name, except for the root directory of shares
57           where it will use the hostname algorithm. Additionally it generates
58           an extid based on the process pid. This can be used to deliberately
59           break lock coherency between all smbd processes in the whole
60           cluster for the root directory of a share.
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62       fileid:mapping = ALGORITHM
63           This option is the legacy version of the fileid:algorithm option,
64           which was used in earlier versions of fileid mapping feature in
65           custom Samba 3.0 versions.
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67       fileid:fstype deny = LIST
68           List of file system types to be ignored for file_id generation.
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70       fileid:fstype allow = LIST
71           List of file system types to be allowed for file_id generation. If
72           this option is set, file system types not listed here are ignored.
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74       fileid:mntdir deny = LIST
75           List of file system mount points to be ignored for file_id
76           generation.
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78       fileid:mntdir allow = LIST
79           List of file system mount points to be allowed for file_id
80           generation. If this option is set, file system mount points not
81           listed here are ignored.
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83       fileid:nolockinode
84           This option triggers use of the fileid hostname algorithm for the
85           configured inode which can be used to deliberately break lock
86           coherency for the corresponding file or directory in a cluster.
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EXAMPLES

89       Usage of the fileid module with the fsid algorithm:
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91                   [global]
92                vfs objects = fileid
93                fileid:algorithm = fsid
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VERSION

96       This man page is part of version 4.13.7 of the Samba suite.
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AUTHOR

99       The original Samba software and related utilities were created by
100       Andrew Tridgell. Samba is now developed by the Samba Team as an Open
101       Source project similar to the way the Linux kernel is developed.
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105Samba 4.13.7                      03/25/2021                     VFS_FILEID(8)
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