Thursday, March 15, 2012

NFS Server Interview Questions

Q. What is NFS?
 NFS is a network file system, which allows remote hosts to mount file system  over a network and interact with those file systems as though they are mounted locally.

Q. NFS uses?
 NFS is used for sharing files and directories throughout the network.

Q. What are the port numbers for nfs?
     2049(nfsd), 111(port map)

Q. what are the demons for nfs?
    Rpc.nfsd, rpc.lockd, rpc.quota.d, rpc.mountd

Q. NFS uses which protocol?
    Nfsv4 uses TCP, nfsv3 and nfsv2 uses UDP

Q: - Explain this entry /shared 192.168.1.0/24(sync,rw)
    Allows all systems with 192.168.1.*  IP addresses read-write access to the  /shared directory


Q: - What will happened if a space is given in between allowed hosts and (options)
If a space is included, the options are applied to any and all IP addresses, which can be quite dangerous if write permission is granted. 


Q: - What is the role of "sync" option for NFS server
sync is used to synchronize the data from server to client. The sync option is recommended because it follows the NFS protocol.


Q: - How to retrieve a list of clients connected to the NFS server?

To retrieve a list of clients connected to the NFS server, use the showmount command
from a shell prompt. To also show the directories the clients are connected to, use the
ex: showmount –e  192.168.0.112

Q: - Name of Configuration file for NFS Server?

/etc/exports


Q: - What is meaning of "no_root_squash" option ?

Treat remote root user as local root. Do not map requests from root to the anonymous user and group ID.


Q: - What is NFS ?

NFS stands for Network File System. NFS was originally developed by Sun Microsystems in the 1980's. NFS allows remote hosts to mount file systems over a network and interact with those file systems as though they are mounted locally. This enables system administrators to consolidate resources onto centralized servers on the network.


Q: - Which NFS versions are available ?

NFS Version 2
NFS Version 3
NFS Version 4


Q: - What is different between NFS Version 2 & 3 ?

nfs 2 default 8kb transfer rate,it did not check the authentication at the time connection.client wants to access unauthorized file it shows error messages like "write error","read error" nfs 3 32kb transfer rate. It check at the time connection- ACL Support

Q: - Can we grant access by Username and password for nfs share?
No, access is granted only for IP address.

Q: - What is the role of "all_squash" option?
Treat all client users as anonymous users. Map all user and group IDs to the anonymous user and group ID.

Q: - What is the role of "root_squash" option?
All requests from the user root are translated or mapped as if they came from the user anonymous (default).

Q: - Explain option "all_squash"?
The UID and GID of exported files are mapped to the user anonymous. It is good for public directories.

Q: - Explain "exportfs" command?
The exportfs command is used to maintain the current table of exported file systems for NFS.

Q: - Explain command "/usr/sbin/exportfs -f"?
It will flush everything out of the kernels export table. Any clients that are active will get new entries added by mountd when they make their next request.

Q: - Which option is used with exportfs command to display the current export list, also displays the list of export options?
exportfs –v

Q: - Which option is used with exportfs command to re-export all directories?
exportfs –r

Q: - Is rpc.mountd daemon supports TCP_WRAPPERS?
Yes, The rpc.mountd daemon is protected by the tcp_wrappers. You have to give the clients access to rpc.mountd if they should be allowed to use NFS Server.

Q: - Explain "nfsstat" command?
The nfsstat command displays the statistics about NFS client and NFS server activity.

Q: - What do you understand by "nfsstat -o all -234" command?
It will Show all information about all versions of NFS.

Q: - What do you understand by "nfsstat --nfs --server -4" command?
It will show statistics for NFS version 4 server.

Q: - Can NFS share mounted on Window XP and Justify your answer?
No, Window XP operating system doesn’t support nfs protocol.

Q: - 192.168.0.117:/data is exported by NFS Server and i want to add this NFS share to client /etc/fstab file. How you will add this entry in /etc/fstab file?
#Device name                      #mount-point    # fs-type     #options      #dump   #fsckorder
192.168.0.117:/data            /mnt                 nfs            defaults              0         0

Q: - Explain "Soft Mounting" option at NFS Client?

if a file request fails, the NFS client will report an error to the process on the client machine requesting the file access. if it cannot be satisfied (for example, the server is down), then it quits. This is called soft mounting.

Q: - Explain "Hard Mounting" option at NFS Client?
If a file request fails, the NFS client will report an error to the process on the client machine requesting the file access. if it cannot be satisfied, then it will not quit until the request is satisfied. This is called Hard mounting.

Q: Explain "intr" option at NFS Client?
Allows nfs requests t be interrupted or killed if the server is unreachable

Q:  Explain "nolock" option at NFS Client?
It disables the file locking and allows the interoperation

Q: - What is "portmap"?
The portmapper keeps a list of what services are running on what ports. This list is used by a connecting machine to see what ports it wants to talk to access certain services.

Q: - How you will check "portmap" service is running or not?
      rpcinfo –p 192.168.0.117

Q: - I am unable to mount a NFS share. How will you trace out the reason?
Firstly, check that you have permissions to mount nfs share or not. Check /etc/exports file.
Secondly you can get RPC error: Program Not Registered (or another "RPC" error)
For this check your NFS server and portmap service running or not by "rpcinfo -p"

Q: Can I modify export permissions without needing to remount clients in order to have them take effect?
Yes. The safest thing to do is edit /etc/exports and run "exportfs -r"

Q. How to restart the services for nfs?
Service nfs restart

Q. How to enable the nfs server after reboot?
Chkconfig  nfs  on



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