Index: head/usr.sbin/mountd/exports.5
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--- head/usr.sbin/mountd/exports.5	(revision 344014)
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 .\"     @(#)exports.5	8.3 (Berkeley) 3/29/95
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-.Dd May 20, 2017
+.Dd Feb 11, 2019
 .Dt EXPORTS 5
 .Os
 .Sh NAME
 .Nm exports
 .Nd define remote mount points for
 .Tn NFS
 mount requests
 .Sh SYNOPSIS
 .Nm
 .Sh DESCRIPTION
 The
 .Nm
 file specifies remote mount points for the
 .Tn NFS
 mount protocol per the
 .Tn NFS
 server specification; see
 .%T "Network File System Protocol Specification" ,
 RFC1094, Appendix A and
 .%T "NFS: Network File System Version 3 Specification" ,
 Appendix I.
 .Pp
 Each line in the file
 (other than comment lines that begin with a #)
 specifies the mount point(s) and export flags within one local server
 file system or the NFSv4 tree root for one or more hosts.
 A long line may be split over several lines by ending all but the
 last line with a backslash
 .Pq Ql \e .
 A host may be specified only once for each local file or the NFSv4 tree root on the
 server and there may be only one default entry for each server
 file system that applies to all other hosts.
 The latter exports the file system to the
 .Dq world
 and should
 be used only when the file system contains public information.
 .Pp
 In a mount entry,
 the first field(s) specify the directory path(s) within a server file system
 that can be mounted on by the corresponding client(s).
 There are three forms of this specification.
 The first is to list all mount points as absolute
 directory paths separated by whitespace.
 This list of directory paths should be considered an
 .Dq administrative control ,
 since it is only enforced by the
 .Xr mountd 8
 daemon and not the kernel.
 As such, it only applies to NFSv2 and NFSv3 mounts and only
 with respect to the client's use of the mount protocol.
 The second is to specify the pathname of the root of the file system
 followed by the
 .Fl alldirs
 flag;
 this form allows the host(s) to mount at any point within the file system,
 including regular files if the
 .Fl r
 option is used on
 .Xr mountd 8 .
 Because NFSv4 does not use the mount protocol,
 the
 .Dq administrative controls
 are not applied and all directories within this server
 file system are mountable via NFSv4 even if the
 .Fl alldirs
 flag has not been specified.
 The third form has the string ``V4:'' followed by a single absolute path
 name, to specify the NFSv4 tree root.
 This line does not export any file system, but simply marks where the root
 of the server's directory tree is for NFSv4 clients.
 The exported file systems for NFSv4 are specified via the other lines
 in the
 .Nm
 file in the same way as for NFSv2 and NFSv3.
 The pathnames must not have any symbolic links in them and should not have
 any
 .Dq Pa \&.
 or
 .Dq Pa ..
 components.
 Mount points for a file system may appear on multiple lines each with
 different sets of hosts and export options.
 .Pp
 The second component of a line specifies how the file system is to be
 exported to the host set.
 The option flags specify whether the file system
 is exported read-only or read-write and how the client UID is mapped to
 user credentials on the server.
 For the NFSv4 tree root, the only option that can be specified in this
 section is
 .Fl sec .
 .Pp
 Export options are specified as follows:
 .Pp
 .Sm off
 .Fl maproot Li = Sy user
 .Sm on
 The credential of the specified user is used for remote access by root.
 The credential includes all the groups to which the user is a member
 on the local machine (see
 .Xr id 1 ) .
 The user may be specified by name or number.
 The user string may be quoted, or use backslash escaping.
 .Pp
 .Sm off
 .Fl maproot Li = Sy user:group1:group2:...
 .Sm on
 The colon separated list is used to specify the precise credential
 to be used for remote access by root.
 The elements of the list may be either names or numbers.
 Note that user: should be used to distinguish a credential containing
 no groups from a complete credential for that user.
 The group names may be quoted, or use backslash escaping.
 .Pp
 .Sm off
 .Fl mapall Li = Sy user
 .Sm on
 or
 .Sm off
 .Fl mapall Li = Sy user:group1:group2:...
 .Sm on
 specifies a mapping for all client UIDs (including root)
 using the same semantics as
 .Fl maproot .
 .Pp
 The option
 .Fl r
 is a synonym for
 .Fl maproot
 in an effort to be backward compatible with older export file formats.
 .Pp
 In the absence of
 .Fl maproot
 and
 .Fl mapall
 options, remote accesses by root will result in using a credential of 65534:65533.
 All other users will be mapped to their remote credential.
 If a
 .Fl maproot
 option is given,
 remote access by root will be mapped to that credential instead of 65534:65533.
 If a
 .Fl mapall
 option is given,
 all users (including root) will be mapped to that credential in
 place of their own.
 .Pp
 .Sm off
 .Fl sec Li = Sy flavor1:flavor2...
 .Sm on
 specifies a colon separated list of acceptable security flavors to be
 used for remote access.
 Supported security flavors are sys, krb5, krb5i and krb5p.
 If multiple flavors are listed, they should be ordered with the most
 preferred flavor first.
 If this option is not present,
 the default security flavor list of just sys is used.
 .Pp
 The
 .Fl ro
 option specifies that the file system should be exported read-only
 (default read/write).
 The option
 .Fl o
 is a synonym for
 .Fl ro
 in an effort to be backward compatible with older export file formats.
 .Pp
 .Tn WebNFS
 exports strictly according to the spec (RFC 2054 and RFC 2055) can
 be done with the
 .Fl public
 flag.
 However, this flag in itself allows r/w access to all files in
 the file system, not requiring reserved ports and not remapping UIDs.
 It
 is only provided to conform to the spec, and should normally not be used.
 For a
 .Tn WebNFS
 export,
 use the
 .Fl webnfs
 flag, which implies
 .Fl public ,
 .Sm off
 .Fl mapall No = Sy nobody
 .Sm on
 and
 .Fl ro .
 Note that only one file system can be
 .Tn WebNFS
 exported on a server.
 .Pp
 A
 .Sm off
 .Fl index No = Pa file
 .Sm on
 option can be used to specify a file whose handle will be returned if
 a directory is looked up using the public filehandle
 .Pq Tn WebNFS .
 This is to mimic the behavior of URLs.
 If no
 .Fl index
 option is specified, a directory filehandle will be returned as usual.
 The
 .Fl index
 option only makes sense in combination with the
 .Fl public
 or
 .Fl webnfs
 flags.
 .Pp
 Specifying the
 .Fl quiet
 option will inhibit some of the syslog diagnostics for bad lines in
 .Pa /etc/exports .
 This can be useful to avoid annoying error messages for known possible
 problems (see
 .Sx EXAMPLES
 below).
 .Pp
 The third component of a line specifies the host set to which the line applies.
 The set may be specified in three ways.
 The first way is to list the host name(s) separated by white space.
 (Standard Internet
 .Dq dot
 addresses may be used in place of names.)
 The second way is to specify a
 .Dq netgroup
 as defined in the
 .Pa netgroup
 file (see
 .Xr netgroup 5 ) .
 The third way is to specify an Internet subnetwork using a network and
 network mask that is defined as the set of all hosts with addresses within
 the subnetwork.
 This latter approach requires less overhead within the
 kernel and is recommended for cases where the export line refers to a
 large number of clients within an administrative subnet.
 .Pp
 The first two cases are specified by simply listing the name(s) separated
 by whitespace.
 All names are checked to see if they are
 .Dq netgroup
 names
 first and are assumed to be hostnames otherwise.
 Using the full domain specification for a hostname can normally
 circumvent the problem of a host that has the same name as a netgroup.
 The third case is specified by the flag
 .Sm off
 .Fl network Li = Sy netname Op Li / Ar prefixlength
 .Sm on
 and optionally
 .Sm off
 .Fl mask No = Sy netmask .
 .Sm on
 The netmask may be specified either by attaching a
 .Ar prefixlength
 to the
 .Fl network
 option, or by using a separate
 .Fl mask
 option.
 If the mask is not specified, it will default to the mask for that network
 class (A, B or C; see
 .Xr inet 4 ) .
 See the
 .Sx EXAMPLES
 section below.
 .Pp
 Scoped IPv6 address must carry scope identifier as documented in
 .Xr inet6 4 .
 For example,
 .Dq Li fe80::%re2/10
 is used to specify
 .Li fe80::/10
 on
 .Li re2
 interface.
 .Pp
 For the third form which specifies the NFSv4 tree root, the directory path
 specifies the location within the server's file system tree which is the
 root of the NFSv4 tree.
 There can only be one NFSv4 root directory per server.
 As such, all entries of this form must specify the same directory path.
 For file systems other than ZFS,
 this location can be any directory and does not
 need to be within an exported file system. If it is not in an exported
 file system, a very limited set of operations are permitted, so that an
 NFSv4 client can traverse the tree to an exported file system.
 Although parts of the NFSv4 tree can be non-exported, the entire NFSv4 tree
 must consist of local file systems capable of being exported via NFS.
 All ZFS file systems in the subtree below the NFSv4 tree root must be
 exported.
 NFSv4 does not use the mount protocol and does permit clients to cross server
 mount point boundaries, although not all clients are capable of crossing the
 mount points.
 .Pp
 The
 .Fl sec
 option on these line(s) specifies what security flavors may be used for
 NFSv4 operations that do not use file handles. Since these operations
 (SetClientID, SetClientIDConfirm, Renew, DelegPurge and ReleaseLockOnwer)
 allocate/modify state in the server, it is possible to restrict some clients to
 the use of the krb5[ip] security flavors, via this option.
 See the
 .Sx EXAMPLES
 section below.
 This third form is meaningless for NFSv2 and NFSv3 and is ignored for them.
 .Pp
 The
 .Xr mountd 8
 utility can be made to re-read the
 .Nm
 file by sending it a hangup signal as follows:
 .Bd -literal -offset indent
 /etc/rc.d/mountd reload
 .Ed
 .Pp
 After sending the
 .Dv SIGHUP ,
 check the
 .Xr syslogd 8
 output to see whether
 .Xr mountd 8
 logged any parsing errors in the
 .Nm
 file.
 .Sh FILES
 .Bl -tag -width /etc/exports -compact
 .It Pa /etc/exports
 the default remote mount-point file
 .El
 .Sh EXAMPLES
 .Bd -literal -offset indent
 /usr /usr/local -maproot=0:10 friends
 /usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16
 /usr -ro -mapall=nobody
 /u -maproot=bin: -network 131.104.48 -mask 255.255.255.0
 /a -network 192.168.0/24
 /a -network 3ffe:1ce1:1:fe80::/64
 /u2 -maproot=root friends
 /u2 -alldirs -network cis-net -mask cis-mask
 /cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0
 /private -sec=krb5i
 /secret -sec=krb5p
 V4: /	-sec=krb5:krb5i:krb5p -network 131.104.48 -mask 255.255.255.0
 V4: /	-sec=sys:krb5:krb5i:krb5p grumpy.cis.uoguelph.ca
 .Ed
 .Pp
 Given that
 .Pa /usr , /u , /a
 and
 .Pa /u2
 are
 local file system mount points, the above example specifies the following:
 .Pp
 The file system rooted at
 .Pa /usr
 is exported to hosts
 .Em friends
 where friends is specified in the netgroup file
 with users mapped to their remote credentials and
 root mapped to UID 0 and group 10.
 It is exported read-write and the hosts in
 .Dq friends
 can mount either
 .Pa /usr
 or
 .Pa /usr/local .
 It is exported to
 .Em 131.104.48.16
 and
 .Em grumpy.cis.uoguelph.ca
 with users mapped to their remote credentials and
 root mapped to the user and groups associated with
 .Dq daemon ;
 it is exported to the rest of the world as read-only with
 all users mapped to the user and groups associated with
 .Dq nobody .
 .Pp
 The file system rooted at
 .Pa /u
 is exported to all hosts on the subnetwork
 .Em 131.104.48
 with root mapped to the UID for
 .Dq bin
 and with no group access.
 .Pp
 The file system rooted at
 .Pa /u2
 is exported to the hosts in
 .Dq friends
 with root mapped to UID and groups
 associated with
 .Dq root ;
 it is exported to all hosts on network
 .Dq cis-net
 allowing mounts at any
 directory within /u2.
 .Pp
 The file system rooted at
 .Pa /a
 is exported to the network 192.168.0.0, with a netmask of 255.255.255.0.
 However, the netmask length in the entry for
 .Pa /a
 is not specified through a
 .Fl mask
 option, but through the
 .Li / Ns Ar prefix
 notation.
 .Pp
 The file system rooted at
 .Pa /a
 is also exported to the IPv6 network
 .Li 3ffe:1ce1:1:fe80::
 address, using the upper 64 bits as the prefix.
 Note that, unlike with IPv4 network addresses, the specified network
 address must be complete, and not just contain the upper bits.
 With IPv6 addresses, the
 .Fl mask
 option must not be used.
 .Pp
 The file system rooted at
 .Pa /cdrom
 will be exported read-only to the entire network 192.168.33.0/24, including
 all its subdirectories.
 Since
 .Pa /cdrom
 is the conventional mountpoint for a CD-ROM device, this export will
 fail if no CD-ROM medium is currently mounted there since that line
 would then attempt to export a subdirectory of the root file system
 with the
 .Fl alldirs
 option which is not allowed.
 The
 .Fl quiet
 option will then suppress the error message for this condition that
 would normally be syslogged.
 As soon as an actual CD-ROM is going to be mounted,
 .Xr mount 8
 will notify
 .Xr mountd 8
 about this situation, and the
 .Pa /cdrom
 file system will be exported as intended.
 Note that without using the
 .Fl alldirs
 option, the export would always succeed.
 While there is no CD-ROM medium mounted under
 .Pa /cdrom ,
 it would export the (normally empty) directory
 .Pa /cdrom
 of the root file system instead.
 .Pp
 The file system rooted at
 .Pa /private
 will be exported using Kerberos 5 authentication and will require
 integrity protected messages for all accesses.
 The file system rooted at
 .Pa /secret
 will also be exported using Kerberos 5 authentication and all messages
 used to access it will be encrypted.
 .Pp
 For the experimental server, the NFSv4 tree is rooted at ``/'',
 and any client within the 131.104.48 subnet is permitted to perform NFSv4 state
 operations on the server, so long as valid Kerberos credentials are provided.
 The machine grumpy.cis.uoguelph.ca is permitted to perform NFSv4 state
 operations on the server using AUTH_SYS credentials, as well as Kerberos ones.
 .Pp
 In the following example some directories are exported as NFSv3 and NFSv4:
 .Bd -literal -offset indent
 V4: /wingsdl/nfsv4
 /wingsdl/nfsv4/usr-ports -maproot=root -network 172.16.0.0 -mask 255.255.0.0
 /wingsdl/nfsv4/clasper   -maproot=root clasper
 .Ed
 .Pp
 Only one V4: line is needed or allowed to declare where NFSv4 is
 rooted.  The other lines declare specific exported directories with
 their absolute paths given in /etc/exports.
 .Pp
 The exported directories' paths are used for both v3 and v4.
 However, they are interpreted differently for v3 and v4.  A client
 mount command for usr-ports would use the server-absolute name when
 using nfsv3:
 .Bd -literal -offset indent
 mount server:/wingsdl/nfsv4/usr-ports /mnt/tmp
 .Ed
 .Pp
 A mount command using NFSv4 would use the path relative to the NFSv4
 root:
 .Bd -literal -offset indent
 mount server:/usr-ports /mnt/tmp
 .Ed
 .Pp
 This also differentiates which version you want if the client can do
 both v3 and v4.  The former will only ever do a v3 mount and the
 latter will only ever do a v4 mount.
 .Pp
 Note that due to different mount behavior between NFSv3 and NFSv4 a
 NFSv4 mount request for a directory that the client does not have
 permission for will succeed and read/write access will fail
 afterwards, whereas NFSv3 rejects the mount request.
 .Sh SEE ALSO
 .Xr nfsv4 4 ,
 .Xr netgroup 5 ,
 .Xr mountd 8 ,
 .Xr nfsd 8 ,
 .Xr showmount 8
 .Sh BUGS
 The export options are tied to the local mount points in the kernel and
 must be non-contradictory for any exported subdirectory of the local
 server mount point.
 It is recommended that all exported directories within the same server
 file system be specified on adjacent lines going down the tree.
 You cannot specify a hostname that is also the name of a netgroup.
 Specifying the full domain specification for a hostname can normally
 circumvent the problem.