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NFS.SYSTEMD(7) Miscellaneous Information Manual NFS.SYSTEMD(7)
nfs.systemd - managing NFS services through systemd.
nfs-utils.service
nfs-server.service
nfs-client.target
etc
The nfs-utils package provides a suite of systemd unit files which
allow the various services to be started and managed. These unit
files ensure that the services are started in the correct order, and
the prerequisites are active before dependant services start. As
there are quite few unit files, it is not immediately obvious how
best to achieve certain results. The following subsections attempt
to cover the issues that are most likely to come up.
Configuration
The standard systemd unit files do not provide any easy way to pass
any command line arguments to daemons so as to configure their
behavior. In many case such configuration can be performed by making
changes to /etc/nfs.conf or other configuration files. When that is
not convenient, a distribution might provide systemd "drop-in" files
which replace the ExecStart= setting to start the program with
different arguments. For example a drop-in file systemd/system/nfs-
mountd.service.d/local.conf containing
[Service]
EnvironmentFile=/etc/sysconfig/nfs
ExecStart=
ExecStart= /usr/sbin/rpc.mountd $RPCMOUNTDOPTS
would cause the nfs-mountd.service unit to run the rpc.mountd program
using, for arguments, the value given for RPCMOUNTDOPTS in
/etc/sysconfig/nfs. This allows for seamless integration with
existing configuration tools.
Enabling unit files
There are three unit files which are designed to be manually enabled.
All others are automatically run as required. The three are:
nfs-client.target
This should be enabled on any host which ever serves as an NFS
client. There is little cost in transparently enabling it
whenever NFS client software is installed.
nfs-server.service
This must be enabled to provide NFS service to clients. It
starts and configures the required daemons in the required
order.
nfs-blkmap.service
The blkmapd daemon is only required on NFS clients which are
using pNFS (parallel NFS), and particularly using the
blocklayout layout protocol. If you might use this particular
extension to NFS, the nfs-blkmap.service unit should be
enabled.
Several other units which might be considered to be optional, such as
rpc-gssd.service are careful to only start if the required
configuration file exists. rpc-gssd.service will not start if the
krb5.keytab file does not exist (typically in /etc).
Restarting NFS services
Most NFS daemons can be restarted at any time. They will reload any
state that they need, and continue servicing requests. This is
rarely necessary though.
When configuration changesare make, it can be hard to know exactly
which services need to be restarted to ensure that the configuration
takes effect. The simplest approach, which is often the best, is to
restart everything. To help with this, the nfs-utils.service unit is
provided. It declares appropriate dependencies with other unit files
so that
systemctl restart nfs-utils
will restart all NFS daemons that are running. This will cause all
configuration changes to take effect except for changes to mount
options lists in /etc/fstab or /etc/nfsmount.conf. Mount options can
only be changed by unmounting and remounting filesystem. This can be
a disruptive operation so it should only be done when the value
justifies the cost. The command
umount -a -t nfs; mount -a -t nfs
should unmount and remount all NFS filesystems.
Masking unwanted services
Rarely there may be a desire to prohibit some services from running
even though there are normally part of a working NFS system. This
may be needed to reduce system load to an absolute minimum, or to
reduce attack surface by not running daemons that are not absolutely
required.
Three particular services which this can apply to are rpcbind,
idmapd, and rpc-gssd. rpcbind is not part of the nfs-utils package,
but it used by several NFS services. However it is not needed when
only NFSv4 is in use. If a site will never use NFSv3 (or NFSv2) and
does not want rpcbind to be running, the correct approach is to run
systemctl mask rpcbind
This will disable rpcbind, and the various NFS services which depend
on it (and are only needed for NFSv3) will refuse to start, without
interfering with the operation of NFSv4 services. In particular,
rpc.statd will not run when rpcbind is masked.
idmapd is only needed for NFSv4, and even then is not needed when the
client and server agree to use user-ids rather than user-names to
identify the owners of files. If idmapd is not needed and not
wanted, it can be masked with
systemctl mask idmapd
rpc-gssd is assumed to be needed if the krb5.keytab file is present.
If a site needs this file present but does not want rpc-gssd running,
it can be masked with
systemctl mask rpc-gssd
/etc/nfs.conf
/etc/nfsmount.conf
/etc/idmapd.conf
systemd.unit(5), nfs.conf(5), nfsmount.conf(5).
This page is part of the nfs-utils (NFS utilities) project.
Information about the project can be found at
⟨http://linux-nfs.org/wiki/index.php/Main_Page⟩. If you have a bug
report for this manual page, see
⟨http://linux-nfs.org/wiki/index.php/Main_Page⟩. This page was
obtained from the project's upstream Git repository
⟨http://git.linux-nfs.org/?p=steved/nfs-utils.git;a=summary⟩ on
2018-02-02. (At that time, the date of the most recent commit that
was found in the repository was 2018-01-17.) If you discover any
rendering problems in this HTML version of the page, or you believe
there is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
NFS.SYSTEMD(7)
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