NFS (Network File System)
A, NFS works
1. What is the NFS server
NFS is the abbreviation for Network File System, which is the biggest feature is that you can through the network, so that different machines, different operating systems can share each other's files.
NFS server can make PC to a network NFS server shared directory is mounted to the local end of the file system, and in the local end system point of view, catalog the remote host is like one of their own disk partition, as in the use very convenient;
2, NFS mounts principle
NFS mount configuration diagram of a server:
As illustrated:
When we set up a shared directory / home / public in the NFS server, the other has access to the NFS server NFS client can mount this directory to a mount point of its own file system, this can mount point their definition, as in FIG client a and client B is not the same end mounted directory. And after you mount all the data we can see the server / home / public locally. If the client server-side configuration of the end of the read-only, then the client will only be able to read-only. If the configuration read-write, clients are able to read and write. Once mounted, NFS client to view the disk information command: #df -h.
Since NFS is for data transmission between server and client over the network, the data to be transferred must have a network port corresponding to think between the two, in the end NFS server which port to use for data transmission it? Basically this NFS server port to open in 2049, but the file system is very complex. Therefore NFS There are other programs to start the extra ports, these additional ports to transfer data is randomly selected, the port is less than 1024 ; since it is random, then the client is aware of how to use the NFS server in the end which port it? Then you need to call (Remote Procedure Call, RPC) protocol remote procedure to achieve it!
3, how RPC and NFS Communications
Because NFS support functions quite a bit, and different functions will use a different program to start, a start of each function will be to enable some port to transmit data, the NFS functionality corresponding port is not fixed , the client wants to know NFS server end of the relevant port to establish a connection for data transmission, and RPC is used for unified management of NFS service port, and the common external port is 111, RPC will record information about NFS port, so we can service and client can be achieved through RPC communication port information. PRC main function is specified for each NFS function corresponding port number, and notifies the client that the client can connect up to a normal port.
So how do you know RPC is NFS function of each port it?
When the first NFS started, it will use some random port, then NFS RPC will go to register these ports, RPC will record these ports, and RPC will open 111 ports, RPC request to wait for the client, if the client there is a request, the server-side RPC will be recorded before the NFS port information to inform the client. So the client will get NFS server port information, the data will be transmitted to the actual port.
Tip: Before you start the NFS SERVER, we must first start the RPC service (ie portmap service, the same below) or NFS SERVER will not be able to register with the RPC service area, in addition, if the RPC service is restarted, the already registered data will be good NFS port all is lost. Therefore, at this time of NFS RPC service management program should be restarted to re-register with the RPC.
Special Note: General NFS modified configuration file is no need to restart NFS, do /etc/init.d/nfs reload or exportfs -rv directly in order to modify the / etc / exports take effect.
4, NFS client and NFS server communication process
1) First, start the RPC server-side service, and open port 111
2) Start the NFS server service, and RPC ports registration information
3) client initiates RPC (portmap service), a service request to the NFS server port server-side RPC (portmap)
4) the server's RPC (portmap) service feedback NFS port information to the client.
5) NFS client and server to establish a connection and transmitting data acquired by the NFS port.
Two, NFS deployment
1, view system information
[root@server7 ~]# cat /etc/redhat-release
CentOS release 7.3.1611 (AltArch)
root@server7 ~]# uname -a
Linux server7.ctos.zu 3.10.0-514.el7.centos.plus.i686 #1 SMP Wed Jan 25 12:55:04 UTC 2017 i686 i686 i386 GNU/LinuxTo develop a habit to check the system version and the kernel parameters. The same software between different versions of the kernel is different, so the method of deployment are not the same, not because of this unnecessary errors.
2, NFS software installation
To deploy Services for NFS, you must install the following two packages: nfs-utils: NFS main program, rpcbind: PRC main program;
Client and NFS server side needs to install these two software.
Note: NFS RPC servers, under Centos5 name for portmap, CentOS6 and lower CentOS7 name rcpbind
NFS software package
utils-NFS: the NFS main program, comprising two rpc.nfsd rpc.mount deamons
the rpcbind: RPC main program
2.1, see NFS software package
[root@server7 ~]# rpm -qa | egrep "nfs|rpcbind"
[root@server7 ~]#
My CentOS release 7.3.1611 is to minimize installation, the default is not installed nfs and rpcbind
Package is the presence of Yum Search
[root@server7 ~]# yum search nfs-utils rpcbind
2.2, install the NFS and RPC services
[root@server7 ~]# yum install nfs-utils rpcbind
[root@server7 ~]# rpm -qa | egrep "nfs|rpcbind"
rpcbind-0.2.0-38.el7_3.1.i686
nfs-utils-1.3.0-0.33.el7_3.i686
libnfsidmap-0.25-15.el7.i686
Check these two packages in the computer what files are installed;
[root@server7 ~]# rpm -ql nfs-utils
3, start the NFS service
3.1, before starting the first start NFS service rpcbind service
View rcpbind state
[root@server7 ~]# systemctl status rpcbind
● rpcbind.service - RPC bind service
Loaded: loaded (/usr/lib/systemd/system/rpcbind.service; indirect; vendor preset: enabled)
Active: active (running) since 一 2017-09-04 10:03:20 CST; 1s ago
Process: 3583 ExecStart=/sbin/rpcbind -w $RPCBIND_ARGS (code=exited, status=0/SUCCESS)
Main PID: 3584 (rpcbind)
CGroup: /system.slice/rpcbind.service
└─3584 /sbin/rpcbind -w
9月 04 10:03:19 server7.ctos.zu systemd[1]: Starting RPC bind service...
9月 04 10:03:20 server7.ctos.zu systemd[1]: Started RPC bind service.
Note: After a successful installation rpcbind default has been opened, and automatically starts to boot. If it does not, then we have to restart the service rcpbind
[root@server7 ~]# systemctl restart rpcbind
Check PRC port
[root@server7 ~]# yum install net-tools lsof
[root@server7 ~]# lsof -i:111
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
systemd 1 root 56u IPv6 43164 0t0 TCP *:sunrpc (LISTEN)
systemd 1 root 57u IPv4 43165 0t0 TCP *:sunrpc (LISTEN)
rpcbind 3584 rpc 4u IPv6 43164 0t0 TCP *:sunrpc (LISTEN)
rpcbind 3584 rpc 5u IPv4 43165 0t0 TCP *:sunrpc (LISTEN)
rpcbind 3584 rpc 8u IPv4 44975 0t0 UDP *:sunrpc
rpcbind 3584 rpc 10u IPv6 44977 0t0 UDP *:sunrpc
[root@server7 ~]# netstat -tlunp |grep rpcbind
udp 0 0 0.0.0.0:111 0.0.0.0:* 3584/rpcbind
udp 0 0 0.0.0.0:791 0.0.0.0:* 3584/rpcbind
udp6 0 0 :::111 :::* 3584/rpcbind
udp6 0 0 :::791 :::* 3584/rpcbind
View NFS NFS service is not started until the port information registered with the PRC
[root@server7 ~]# rpcinfo -p localhost
program vers proto port service
100000 4 tcp 111 portmapper
100000 3 tcp 111 portmapper
100000 2 tcp 111 portmapper
100000 4 udp 111 portmapper
100000 3 udp 111 portmapper
100000 2 udp 111 portmapper
3.2, RPC service starts and then start the NFS service
View Status
[root@server7 ~]# systemctl status nfs
● nfs-server.service - NFS server and services
Loaded: loaded (/usr/lib/systemd/system/nfs-server.service; disabled; vendor preset: disabled)
Active: inactive (dead)
The default is not started, do not start after the system power-on reset, start the nfs service will be set to boot.
[root@server7 ~]# systemctl start nfs
[root@server7 ~]# systemctl enable nfs
Created symlink from /etc/systemd/system/multi-user.target.wants/nfs-server.service to /usr/lib/systemd/system/nfs-server.service.
[root@server7 ~]# systemctl status nfs
● nfs-server.service - NFS server and services
Loaded: loaded (/usr/lib/systemd/system/nfs-server.service; enabled; vendor preset: disabled)
Active: active (exited) since 一 2017-09-04 10:15:21 CST; 19s ago
Main PID: 3654 (code=exited, status=0/SUCCESS)
CGroup: /system.slice/nfs-server.service
9月 04 10:15:21 server7.ctos.zu systemd[1]: Starting NFS server and services...
9月 04 10:15:21 server7.ctos.zu systemd[1]: Started NFS server and services.
After starting the NFS Once again, we see the port of registration information rpc
[root@server7 ~]# rpcinfo -p localhost
program vers proto port service
100000 4 tcp 111 portmapper
100000 3 tcp 111 portmapper
100000 2 tcp 111 portmapper
100000 4 udp 111 portmapper
100000 3 udp 111 portmapper
100000 2 udp 111 portmapper
100024 1 udp 56626 status
100024 1 tcp 42691 status
100005 1 udp 20048 mountd
100005 1 tcp 20048 mountd
100005 2 udp 20048 mountd
100005 2 tcp 20048 mountd
100005 3 udp 20048 mountd
100005 3 tcp 20048 mountd
100003 3 tcp 2049 nfs
100003 4 tcp 2049 nfs
100227 3 tcp 2049 nfs_acl
100003 3 udp 2049 nfs
100003 4 udp 2049 nfs
100227 3 udp 2049 nfs_acl
100021 1 udp 57225 nlockmgr
100021 3 udp 57225 nlockmgr
100021 4 udp 57225 nlockmgr
100021 1 tcp 35665 nlockmgr
100021 3 tcp 35665 nlockmgr
100021 4 tcp 35665 nlockmgr
After confirming useless startup problems we take a look at NFS in the end open which ports
[root@server7 ~]# netstat -tulnp |grep -E '(rpc|nfs)'
tcp 0 0 0.0.0.0:42691 0.0.0.0:* LISTEN 3634/rpc.statd
tcp 0 0 0.0.0.0:20048 0.0.0.0:* LISTEN 3642/rpc.mountd
tcp6 0 0 :::39614 :::* LISTEN 3634/rpc.statd
tcp6 0 0 :::20048 :::* LISTEN 3642/rpc.mountd
udp 0 0 127.0.0.1:842 0.0.0.0:* 3634/rpc.statd
udp 0 0 0.0.0.0:20048 0.0.0.0:* 3642/rpc.mountd
udp 0 0 0.0.0.0:111 0.0.0.0:* 3584/rpcbind
udp 0 0 0.0.0.0:791 0.0.0.0:* 3584/rpcbind
udp 0 0 0.0.0.0:56626 0.0.0.0:* 3634/rpc.statd
udp6 0 0 :::56122 :::* 3634/rpc.statd
udp6 0 0 :::20048 :::* 3642/rpc.mountd
udp6 0 0 :::111 :::* 3584/rpcbind
udp6 0 0 :::791 :::* 3584/rpcbind
4, NFS common process Detailed
[root@server7 ~]# ps -ef |egrep "rpc|nfs“
rpc 3584 1 0 10:03 ? 00:00:00 /sbin/rpcbind -w
rpcuser 3634 1 0 10:15 ? 00:00:00 /usr/sbin/rpc.statd --no-notify
root 3637 2 0 10:15 ? 00:00:00 [rpciod]
root 3642 1 0 10:15 ? 00:00:00 /usr/sbin/rpc.mountd
root 3652 1 0 10:15 ? 00:00:00 /usr/sbin/rpc.idmapd
root 3657 2 0 10:15 ? 00:00:00 [nfsd4_callbacks]
root 3663 2 0 10:15 ? 00:00:00 [nfsd]
root 3664 2 0 10:15 ? 00:00:00 [nfsd]
root 3665 2 0 10:15 ? 00:00:00 [nfsd]
root 3666 2 0 10:15 ? 00:00:00 [nfsd]
root 3667 2 0 10:15 ? 00:00:00 [nfsd]
root 3668 2 0 10:15 ? 00:00:00 [nfsd]
root 3669 2 0 10:15 ? 00:00:00 [nfsd]
root 3670 2 0 10:15 ? 00:00:00 [nfsd]
root 3705 3267 0 10:23 pts/0 00:00:00 grep -E --color=auto rpc|nfs
-
nfsd
The main NFS service provider, this daemon main function is to manage whether the client can use the server file system mount information, which also includes determining the user's login ID.
-
rpc.mountd
This daemon main function is to manage the NFS file system. When the client end successfully passed rpc.nfsd login host before it can use the NFS server specified file, the file will go through the certification process using privileges. It will go to read NFS configuration file / etc / exports to compare the client's permission, when overcome this obstacle, client end will get permission to use the NFS file.
-
rpc.lockd (non-essential)
This daemon is used to manage file locking aspect, when multiple clients simultaneously attempt to write to a file it can cause some problems to the file. rpc.lockd can be used to overcome this problem. But rpc.lockd must be both the client and the server are turned down.
-
rpc.statd (non-essential)
This daemon can be used to check the consistency of the file, if it occurs because the clients use the same cause file corruption when a file, rpc.statd can be used to detect and attempt to recover the file
5. Configure the NFS Service
NFS software is very simple, the main configuration file: / etc / exports, the default content inside is empty, if it does not, you can use vim take the initiative to create the file. As also set up NFS server is as simple as editing the main configuration file / etc / exports after the first start rpcbind (if already started, do not restart), then start nfs, NFS success.
Then the / etc / exports should be how to set?
[root@server7 etc]# vi /etc/exports
/tmp/data 192.168.1.0/24(ro) client-A.ctos.zu(rw,sync)
# [Shared directory] [Client Address 1 (permissions)] [Client Address 2 (authority)]
The above is a simple case of configuration, each front row is to be shared out directory, pay attention to is the directory unit
Shared directory: present in our directory on the machine, we want to share it with other hosts on the network use. If I want to share / tmp / data directory, then this option can directly write / tmp / data directory, which can be shared to different hosts in accordance with different permissions.
A client address (parameter 1, parameter 2): a client network address can be provided, a single host may be provided. Parameters: such as read and write permissions rw, sync update sync, compression visiting the account all_squash, anonymous account anonuid compressed = uid, anongid = gid, and so on;
Set client address mainly in the following ways:
1), you can use the full IP network or a number, e.g. 192.168.100.100 or 192.168.8.0/24
2), you can use a host name, but the host name must be in the / etc / hosts, or you can use DNS to find the name of the job, anyway, the focus is to find the IP on the line, if the host name, you can also support wildcards, For example '*' or '? 'Acceptable; for example: host [1-8] .ctos.zu, server .test.com?
NFS permissions
NFS configuration permissions, i.e., / etc / exports configuration file format small brackets () in the set of parameters;
| Parameters command |
Parameter Purpose |
| rw |
Represents read and write |
| ro |
Read-only means that only read access |
| Sync |
After the request or write data, the data synchronous writes to the hard disk NFS server will return |
| no_root_squas |
Nfs server users to access a shared directory if you are root, then it has root access to the directory. This configuration was originally prepared for the diskless users. Users should avoid using! |
| root_squash |
NFS server for users to access the shared directory, if you are root, then nobody will be compressed into a user's identity. |
| all_squash |
Regardless of the shared directory access nfs server user identity including root, its authority will be compressed into an anonymous user, and they will become the udi and gid or uid nobody nfsnobody accounts, gid. Read and write data simultaneously in multiple nfs server nfs client, this parameter is useful to ensure that all data written permission of the same. But there are different systems might anonymous users uid, different gid. Because here we need between the user and client service are the same. For example: the server specified anonymous user's UID is 2000, then the client also must exist before 2000 this account can |
| anonuid |
anonuid is anonymous uid and gid. Description Client what permissions to access the service side, is nfsnobody by default. Uid65534. |
| anongid |
With anongid, it is to replace the uid gid it |
Instance:
/home/test 1192.168.1.0/24(rw,sync,all_squash,anonuid=2000,anongid=2000)
### Note that the red part can not have spaces! ! Production environment commonly used configuration for a multi-client shared NFS directory. All_squash That no matter what capacity the client is to visit, will be compressed into the ground behind all_squash user and group identity. Here with anonuid, anongid number to mark. =
summary:
Shared server configuration format:
1) Basic format: shared directory ip / 24 (shared property) -> without spaces Note
2) share permissions:
rw read-write property
sync files written to disk before the actual return
all_squash: all the user access to the user are compressed into a subsequent contact.
anonuid: User default compression
anongid: default compression user group
Then the client to access in what capacity?
Client Access server default is to use nfsnobody the user to visit. uid and gid 65534. When the default server share, but also added all_squash this parameter. And to develop anonuid 65534 (that is, nfsnobayd user). Of course, if the system is nfsnobody other uid, then it may cause access problems. So the best we can set up a user to access a unified UID, GID.
How do I mount situation?
There are two important documents, can solve this question. / Var / lib / nfs / etab, / var / lib / nfs / rmtab these two files on the server will be able to see what shared directory, in the end how much the client to mount a share, and you can view the client's specific mount information.
1, etab this file can see the shared directory on the server which performs who can use, and set the parameters why.
2, rmtab this document is to be able to view the situation shared directory is mounted.
