1exportfs(8) System Manager's Manual exportfs(8)
2
6 exportfs - maintain table of exported NFS file systems
7
9 /usr/sbin/exportfs [-avi] [-o options,..] [client:/path ..]
10 /usr/sbin/exportfs -r [-v]
11 /usr/sbin/exportfs [-av] -u [client:/path ..]
12 /usr/sbin/exportfs [-v]
13 /usr/sbin/exportfs -f
14
16 An NFS server maintains a table of local physical file systems that are
17 accessible to NFS clients. Each file system in this table is referred
18 to as an exported file system, or export, for short.
19 The exportfs command maintains the current table of exports for the NFS
21 server. The master export table is kept in a file named
22 /var/lib/nfs/etab. This file is read by rpc.mountd when a client sends
23 an NFS MOUNT request.
24 Normally the master export table is initialized with the contents of
26 /etc/exports and files under /etc/exports.d by invoking exportfs -a.
27 However, a system administrator can choose to add or delete exports
28 without modifying /etc/exports or files under /etc/exports.d by using
29 the exportfs command.
30 exportfs and its partner program rpc.mountd work in one of two modes: a
32 legacy mode which applies to 2.4 and earlier versions of the Linux ker‐
33 nel, and a new mode which applies to 2.6 and later versions, providing
34 the nfsd virtual filesystem has been mounted at /proc/fs/nfsd or
35 /proc/fs/nfs. On 2.6 kernels, if this filesystem is not mounted, the
36 legacy mode is used.
37 In the new mode, exportfs does not give any information to the kernel,
39 but provides it only to rpc.mountd through the /var/lib/nfs/etab file.
40 rpc.mountd then manages kernel requests for information about exports,
41 as needed.
42 In the legacy mode, exports which identify a specific host, rather than
44 a subnet or netgroup, are entered directly into the kernel's export ta‐
45 ble, as well as being written to /var/lib/nfs/etab. Further, exports
46 listed in /var/lib/nfs/rmtab which match a non host-specific export
47 request will cause an appropriate export entry for the host given in
48 rmtab to be added to the kernel's export table.
49
51 -a Export or unexport all directories.
52 -o options,...
54 Specify a list of export options in the same manner as in
55 exports(5).
56 -i Ignore the /etc/exports file and files under /etc/exports.d
58 directory. Only default options and options given on the com‐
59 mand line are used.
60 -r Reexport all directories, synchronizing /var/lib/nfs/etab with
62 /etc/exports and files under /etc/exports.d. This option
63 removes entries in /var/lib/nfs/etab which have been deleted
64 from /etc/exports or files under /etc/exports.d, and removes any
65 entries from the kernel export table which are no longer valid.
66 -u Unexport one or more directories.
68 -f If /proc/fs/nfsd or /proc/fs/nfs is mounted, flush everything
70 out of the kernel's export table. Fresh entries for active
71 clients are added to the kernel's export table by rpc.mountd
72 when they make their next NFS mount request.
73 -v Be verbose. When exporting or unexporting, show what's going on.
75 When displaying the current export list, also display the list
76 of export options.
77
79 Exporting Directories
80 The first synopsis shows how to invoke exportfs when adding new entries
81 to the export table. When using exportfs -a, all exports listed in
82 /etc/exports and files under /etc/exports.d are added to
83 /var/lib/nfs/etab. The kernel's export table is also updated as
84 needed.
85 The host:/path argument specifies a local directory to export, along
87 with the client or clients who are permitted to access it. See
88 exports(5) for a description of supported options and access list for‐
89 mats.
90 IPv6 presentation addresses contain colons, which are already used to
92 separate the "host" and "path" command line arguments. When specifying
93 a client using a raw IPv6 address, enclose the address in square brack‐
94 ets. For IPv6 network addresses, place the prefix just after the clos‐
95 ing bracket.
96 To export a directory to the world, simply specify :/path.
98 The export options for a particular host/directory pair derive from
100 several sources. The default export options are
101 sync,ro,root_squash,wdelay. These can be overridden by entries in
102 /etc/exports or files under /etc/exports.d.
103 A system administrator may override options from these sources using
105 the -o command-line option on exportfs. This option takes a comma-sep‐
106 arated list of options in the same fashion as one would specify them in
107 /etc/exports. In this way exportfs can be used to modify the export
108 options of an already exported directory.
109 Unexporting Directories
111 The third synopsis shows how to unexported a currently exported direc‐
112 tory. When using exportfs -ua, all entries listed in /var/lib/nfs/etab
113 are removed from the kernel export tables, and the file is cleared.
114 This effectively shuts down all NFS activity.
115 To remove an export, specify a host:/path pair. This deletes the speci‐
117 fied entry from /var/lib/nfs/etab and removes the corresponding kernel
118 entry (if any).
119 Dumping the Export Table
121 Invoking exportfs without options shows the current list of exported
122 file systems. Adding the -v option causes exportfs to display the
123 export options for each export.
124
126 The following adds all directories listed in /etc/exports and files
127 under /etc/exports.d to /var/lib/nfs/etab and pushes the resulting
128 export entries into the kernel:
129 # exportfs -a
131 To export the /usr/tmp directory to host django, allowing insecure file
133 locking requests from clients:
134 # exportfs -o insecure_locks django:/usr/tmp
136 To unexport the /usr/tmp directory:
138 # exportfs -u django:/usr/tmp
140 To unexport all exports listed in /etc/exports and files under
142 /etc/exports.d:
143 # exportfs -au
145 To export the /usr/tmp directory to IPv6 link-local clients:
147 # exportfs [fe80::]/64:/usr/tmp
149
151 Exporting to IP networks or DNS and NIS domains does not enable clients
152 from these groups to access NFS immediately. Rather, these sorts of
153 exports are hints to rpc.mountd(8) to grant any mount requests from
154 these clients. This is usually not a problem, because any existing
155 mounts are preserved in rmtab across reboots.
156 When unexporting a network or domain entry, any current exports to mem‐
158 bers of this group will be checked against the remaining valid exports
159 and if they themselves are no longer valid they will be removed.
160
162 /etc/exports input file listing exports, export options,
163 and access control lists
164 /etc/exports.d directory where extra input files are stored.
166 Note: only files that end with .exports are
167 used.
168 /var/lib/nfs/etab master table of exports
170 /var/lib/nfs/rmtab table of clients accessing server's exports
172
174 exports(5), rpc.mountd(8), netgroup(5)
175
177 Olaf Kirch <okir@monad.swb.de>
178 Neil Brown <neilb@cse.unsw.edu.au>
179 31 December 2009 exportfs(8)