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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
(see nfs.conf(5)). 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
Also similar files in /usr/etc and in related conf.d drop-in
directories.
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
⟨git://git.linux-nfs.org/projects/steved/nfs-utils.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-05-10.) 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 [email protected]
NFS.SYSTEMD(7)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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