SHARE_NFS(8) Maintenance Commands and Procedures SHARE_NFS(8)

NAME

share_nfs - make local NFS file systems available for mounting by remote
systems

SYNOPSIS

share [-d description] [-F nfs] [-o specific_options] pathname

DESCRIPTION

The share utility makes local file systems available for mounting by remote
systems. It starts the nfsd(8) and mountd(8) daemons if they are not
already running.

If no argument is specified, then share displays all file systems currently
shared, including NFS file systems and file systems shared through other
distributed file system packages.

OPTIONS

The following options are supported:

-d description
Provide a comment that describes the file system to be shared.

-F nfs Share NFS file system type.

-o specific_options
Specify specific_options in a comma-separated list of keywords
and attribute-value-assertions for interpretation by the file-
system-type-specific command. If specific_options is not
specified, then by default sharing is read-write to all clients.
specific_options can be any combination of the following:

aclok Allows the NFS server to do access control for NFS
Version 2 clients (running SunOS 2.4 or earlier). When
aclok is set on the server, maximal access is given to
all clients. For example, with aclok set, if anyone
has read permissions, then everyone does. If aclok is
not set, minimal access is given to all clients.

anon=uid Set uid to be the effective user ID of unknown users.
By default, unknown users are given the effective user
ID UID_NOBODY. If uid is set to -1, access is denied.

charset=access_list
Where charset is one of: euc-cn, euc-jp, euc-jpms, euc-
kr, euc-tw, iso8859-1, iso8859-2, iso8859-5, iso8859-6,
iso8859-7, iso8859-8, iso8859-9, iso8859-13,
iso8859-15, koi8-r.

Clients that match the access_list for one of these
properties will be assumed to be using that character
set and file and path names will be converted to UTF-8
for the server.

gidmap=mapping[~mapping]...
Where mapping is: [clnt]:[srv]:access_list

Allows remapping the group ID (gid) in the incoming
request to some other gid. This effectively changes
the identity of the user in the request to that of some
other local user.

For clients where the gid in the incoming request is
clnt and the client matches the access_list, change the
group ID to srv. If clnt is asterisk (*), all groups
are mapped by this rule. If clnt is omitted, all
unknown groups are mapped by this rule. If srv is set
to -1, access is denied. If srv is omitted, the gid is
mapped to UID_NOBODY.

The particular mappings are separated in the gidmap=
option by tilde (~) and are evaluated in the specified
order until a match is found. Both root= and
root_mapping= options (if specified) are evaluated
before the gidmap= option. The gidmap= option is
skipped in the case where the client matches the root=
option.

The gidmap= option is evaluated before the anon=
option.

This option is supported only for AUTH_SYS.

index=file
Load file rather than a listing of the directory
containing this file when the directory is referenced
by an NFS URL.

log[=tag]
Enables NFS server logging for the specified file
system. The optional tag determines the location of
the related log files. The tag is defined in
/etc/nfs/nfslog.conf. If no tag is specified, the
default values associated with the global tag in
/etc/nfs/nfslog.conf are used. Support of NFS server
logging is only available for NFS Version 2 and Version
3 requests.

nohide By default, if server exports two filesystems, one of
which is mounted as a child of the other, NFS Version 2
and Version 3 clients must mount both filesystems
explicitly in order to access them. If a client only
mounts the parent, it will see an empty directory at
the location where the other filesystem is mounted.

Setting the nohide option on a filesystem causes it to
no longer be hidden in this manner, and the client will
be able to move from the parent filesystem to this one
without noticing the change. However, some NFS clients
or applications may not function correctly when this
option is used. In particular, files on different
underlying filesystems may appear to have the same
inode numbers. The nohide option only applies to NFS
Version 2 and Version 3 requests.

noaclfab By default, the NFS server will fabricate POSIX-draft
style ACLs in response to ACL requests from NFS Version
2 or Version 3 clients accessing shared file systems
that do not support POSIX-draft ACLs (such as ZFS).
Specifying noaclfab disables this behavior.

none=access_list
Access is not allowed to any client that matches the
access list. The exception is when the access list is
an asterisk (*), in which case ro or rw can override
none.

nosub Prevents clients from mounting subdirectories of shared
directories. For example, if /export is shared with
the nosub option on server "fooey" then a NFS client
cannot do:

mount -F nfs fooey:/export/home/mnt

NFS Version 4 does not use the MOUNT protocol. The
nosub option only applies to NFS Version 2 and Version
3 requests.

nosuid By default, clients are allowed to create files on the
shared file system with the setuid or setgid mode
enabled. Specifying nosuid causes the server file
system to silently ignore any attempt to enable the
setuid or setgid mode bits.

public Moves the location of the public file handle from root
(/) to the exported directory for WebNFS-enabled
browsers and clients. This option does not enable
WebNFS service; WebNFS is always on. Only one file
system per server may use this option. Any other
option, including the ro=list and rw=list options can
be included with the public option.

ro Sharing is read-only to all clients.

ro=access_list
Sharing is read-only to the clients listed in
access_list; overrides the rw suboption for the clients
specified. See access_list below.

root=access_list
Only root users from the hosts specified in access_list
have root access. See access_list below. By default,
no host has root access, so root users are mapped to an
anonymous user ID (see the anon=uid option described
above). Netgroups can be used if the file system
shared is using UNIX authentication (AUTH_SYS).

root_mapping=uid
For a client that is allowed root access, map the root
UID to the specified user id.

rw Sharing is read-write to all clients.

rw=access_list
Sharing is read-write to the clients listed in
access_list; overrides the ro suboption for the clients
specified. See access_list below.

sec=mode[:mode]...
Sharing uses one or more of the specified security
modes. The mode in the sec=mode option must be a mode
name supported on the client. If the sec= option is
not specified, the default security mode used is
AUTH_SYS. Multiple sec= options can be specified on
the command line, although each mode can appear only
once. The security modes are defined in nfssec(7).

Each sec= option specifies modes that apply to any
subsequent window=, rw, ro, rw=, ro=, and root= options
that are provided before another sec= option. Each
additional sec= resets the security mode context, so
that more window=, rw, ro, rw=, ro=, and root= options
can be supplied for additional modes.

sec=none If the option sec=none is specified when the client
uses AUTH_NONE, or if the client uses a security mode
that is not one that the file system is shared with,
then the credential of each NFS request is treated as
unauthenticated. See the anon=uid option for a
description of how unauthenticated requests are
handled.

secure This option has been deprecated in favor of the sec=dh
option.

uidmap=mapping[~mapping]...
Where mapping is: [clnt]:[srv]:access_list

Allows remapping the user ID (uid) in the incoming
request to some other uid. This effectively changes
the identity of the user in the request to that of some
other local user.

For clients where the uid in the incoming request is
clnt and the client matches the access_list, change the
user ID to srv. If clnt is asterisk (*), all users are
mapped by this rule. If clnt is omitted, all unknown
users are mapped by this rule. If srv is set to -1,
access is denied. If srv is omitted, the uid is mapped
to UID_NOBODY.

The particular mappings are separated in the uidmap=
option by tilde (~) and are evaluated in the specified
order until a match is found. Both root= and
root_mapping= options (if specified) are evaluated
before the uidmap= option. The uidmap= option is
skipped in the case where the client matches the root=
option.

The uidmap= option is evaluated before the anon=
option.

This option is supported only for AUTH_SYS.

window=value
When sharing with sec=dh, set the maximum life time (in
seconds) of the RPC request's credential (in the
authentication header) that the NFS server allows. If
a credential arrives with a life time larger than what
is allowed, the NFS server rejects the request. The
default value is 30000 seconds (8.3 hours).

access_list
The access_list argument is a colon-separated list whose components may be
any number of the following:

hostname The name of a host. With a server configured for DNS or LDAP
naming in the nsswitch hosts entry, any hostname must be
represented as a fully qualified DNS or LDAP name.

netgroup A netgroup contains a number of hostnames. With a server
configured for DNS or LDAP naming in the nsswitch hosts entry,
any hostname in a netgroup must be represented as a fully
qualified DNS or LDAP name.

domain name suffix
To use domain membership the server must use DNS or LDAP to
resolve hostnames to IP addresses; that is, the hosts entry in
the /etc/nsswitch.conf must specify dns or ldap ahead of nis
since only DNS and LDAP return the full domain name of the host.
Other name services like NIS cannot be used to resolve hostnames
on the server because when mapping an IP address to a hostname
they do not return domain information. For example,

NIS 172.16.45.9 --> "myhost"

and

DNS or LDAP 172.16.45.9 --> "myhost.mydomain.example.com"

The domain name suffix is distinguished from hostnames and
netgroups by a prefixed dot. For example,

rw=.mydomain.example.com

A single dot can be used to match a hostname with no suffix. For
example,

rw=.

matches "mydomain" but not "mydomain.example.com". This feature
can be used to match hosts resolved through NIS rather than DNS
and LDAP.

network The network or subnet component is preceded by an at-sign (@).
It can be either a name or a dotted address. If a name, it is
converted to a dotted address by getnetbyname(3SOCKET). For
example,

=@mynet

would be equivalent to:

=@172.16 or =@172.16.0.0

The network prefix assumes an octet-aligned netmask determined
from the zeroth octet in the low-order part of the address up to
and including the high-order octet, if you want to specify a
single IP address (see below). In the case where network
prefixes are not byte-aligned, the syntax allows a mask length to
be specified explicitly following a slash (/) delimiter. For
example,

=@theothernet/17 or =@172.16.132/22

where the mask is the number of leftmost contiguous significant
bits in the corresponding IP address.

When specifying individual IP addresses, use the same @ notation
described above, without a netmask specification. For example:

=@172.16.132.14

Multiple, individual IP addresses would be specified, for
example, as:

root=@172.16.132.20:@172.16.134.20

A prefixed minus sign (-) denies access to that component of access_list.
The list is searched sequentially until a match is found that either grants
or denies access, or until the end of the list is reached. For example, if
host "terra" is in the "engineering" netgroup, then

rw=-terra:engineering

denies access to "terra" but

rw=engineering:-terra

grants access to "terra".

OPERANDS

The following operands are supported:

pathname The pathname of the file system to be shared.

FILES

/etc/dfs/fstypes list of system types, NFS by default

/etc/dfs/sharetab system record of shared file systems

/etc/nfs/nfslogtab system record of logged file systems

/etc/nfs/nfslog.conf logging configuration file

EXIT STATUS

The share_nfs utility exits 0 on success, and >0 if an error occurs.

EXAMPLES

Example 1 Sharing A File System With Logging Enabled
The following example shows the /export file system shared with logging
enabled:

share -o log /export

The default global logging parameters are used since no tag identifier is
specified. The location of the log file, as well as the necessary logging
work files, is specified by the global entry in /etc/nfs/nfslog.conf. The
nfslogd(8) daemon runs only if at least one file system entry in
/etc/dfs/dfstab is shared with logging enabled upon starting or rebooting
the system. Simply sharing a file system with logging enabled from the
command line does not start the nfslogd(8).

Example 2 Remap A User Coming From The Particular NFS Client
The following example remaps the user with uid 100 at client 10.0.0.1 to
user joe:

share -o uidmap=100:joe:@10.0.0.1 /export

SEE ALSO

getnetbyname(3SOCKET), netgroup(5), nfslog.conf(5), acl(7), attributes(7),
nfssec(7), mount(8), mountd(8), nfsd(8), nfslogd(8), share(8), unshare(8)

NOTES

If the sec= option is presented at least once, all uses of the window=, rw,
ro, rw=, ro=, and root= options must come after the first sec= option. If
the sec= option is not presented, then sec=sys is implied.

If one or more explicit sec= options are presented, sys must appear in one
of the options mode lists for accessing using the AUTH_SYS security mode to
be allowed. For example:

share -F nfs /var
share -F nfs -o sec=sys /var

grants read-write access to any host using AUTH_SYS, but

share -F nfs -o sec=dh /var

grants no access to clients that use AUTH_SYS.

Unlike previous implementations of share_nfs, access checking for the
window=, rw, ro, rw=, and ro= options is done per NFS request, instead of
per mount request.

Combining multiple security modes can be a security hole in situations
where the ro= and rw= options are used to control access to weaker security
modes. In this example,

share -F nfs -o sec=dh,rw,sec=sys,rw=hosta /var

an intruder can forge the IP address for "hosta" (albeit on each NFS
request) to side-step the stronger controls of AUTH_DES. Something like:

share -F nfs -o sec=dh,rw,sec=sys,ro /var

is safer, because any client (intruder or legitimate) that avoids AUTH_DES
only gets read-only access. In general, multiple security modes per share
command should only be used in situations where the clients using more
secure modes get stronger access than clients using less secure modes.

If rw= and ro= options are specified in the same sec= clause, and a client
is in both lists, the order of the two options determines the access the
client gets. If client "hosta" is in two netgroups, "group1" and "group2",
in this example, the client would get read-only access:

share -F nfs -o ro=group1,rw=group2 /var

In this example "hosta" would get read-write access:

share -F nfs -o rw=group2,ro=group1 /var

If within a sec= clause, both the ro and rw= options are specified, for
compatibility, the order of the options rule is not enforced. All hosts
would get read-only access, with the exception to those in the read-write
list. Likewise, if the ro= and rw options are specified, all hosts get
read-write access with the exceptions of those in the read-only list.

The ro= and rw= options are guaranteed to work over UDP and TCP but may not
work over other transport providers.

The root= option with AUTH_SYS is guaranteed to work over UDP and TCP but
may not work over other transport providers.

The root= option with AUTH_DES is guaranteed to work over any transport
provider.

There are no interactions between the root= option and the rw, ro, rw=, and
ro= options. Putting a host in the root list does not override the
semantics of the other options. The access the host gets is the same as
when the root= option is absent. For example, the following share command
denies access to "hostb":

share -F nfs -o ro=hosta,root=hostb /var

The following gives read-only permissions to "hostb":

share -F nfs -o ro=hostb,root=hostb /var

The following gives read-write permissions to "hostb":

share -F nfs -o ro=hosta,rw=hostb,root=hostb /var

If the file system being shared is a symbolic link to a valid pathname, the
canonical path (the path which the symbolic link follows) is shared. For
example, if /export/foo is a symbolic link to /export/bar, the following
share command results in /export/bar as the shared pathname (and not
/export/foo):

share -F nfs /export/foo

An NFS mount of server:/export/foo results in server:/export/bar really
being mounted.

This line in the /etc/dfs/dfstab file shares the /disk file system read-
only at boot time:

share -F nfs -o ro /disk

The mountd(8) process allows the processing of a path name that contains a
symbolic link. This allows the processing of paths that are not themselves
explicitly shared with share_nfs. For example, /export/foo might be a
symbolic link that refers to /export/bar which has been specifically
shared. When the client mounts /export/foo the mountd processing follows
the symbolic link and responds with the /export/bar. The NFS Version 4
protocol does not use the mountd processing and the client's use of
/export/foo does not work as it does with NFS Version 2 and Version 3 and
the client receives an error when attempting to mount /export/foo.

The nohide option violates RFC 1094, Network File System Protocol
Specification and RFC 1813, NFS: Network File System Version 3 Protocol
Specification

The nohide option is provided for compatibility with Linux NFS.

illumos November 22, 2021 illumos