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Network File System. Peter DSouza. NFS. Allows machines to mount a disk partition on a remote machine as if it were a local drive Other systems similar to NFS – AFS CODA. Setting up NFS server. Configuration files /etc/exports (required) /etc/hosts.allow (optional)
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Network File System Peter DSouza
NFS • Allows machines to mount a disk partition on a remote machine as if it were a local drive • Other systems similar to NFS – • AFS • CODA
Setting up NFS server • Configuration files • /etc/exports (required) • /etc/hosts.allow (optional) • /etc/hosts.deny (optional)
Setting up NFS server(Contd.) • /etc/exports directory machine1(option11,option12) machine2(option21,option22) eg. /usr/local 192.168.0.1(ro) 192.168.0.2(ro) /home 192.168.0.1(rw) 192.168.0.2(rw) • /etc/hosts.allow service: host [or network/netmask] , host [or network/netmask] eg. portmap: 192.168.0.1 , 192.168.0.2 • /etc/hosts.deny portmap:ALL lockd:ALL mountd:ALL ….
Setting up NFS server(Contd.) • Starting and stopping NFS /sbin/service nfs start /sbin/service nfs stop /sbin/service nfs reload • Reloading /etc/exports exportfs -ra
Setting up NFS client • Using mount command mount server:directory/directory mount_point eg. mount master.foo.com:/home /mnt/home • Using /etc/fstab device mntpt fs-type options dump fsckorder eg. master.foo.com:/home /pub nfs rw 0 0 mount /pub
Setting up NFS client(Contd.) • Using autofs auto.master /misc /etc/auto.misc --timeout 60 auto.misc myproject -rw,soft,intr,rsize=8192,wsize=8192 penguin.host.net:/project52 /sbin/service autofs restart
Optimizing NFS performance • Setting Block Size to Optimize Transfer Speeds • Modify rsize and wsize values to control size of chunks of data between server and client • Default – 4096 • Packet size and network drivers • Important when NFS is used over UDP • Number of instances of NFSD • typically 8 instances • Increase number of instances to match traffic
Optimizing NFS performance (Contd). • Memory limits on Input Queue • Increase to at least 256k, restart nfsd, then restore memory limits echo 262144 > /proc/sys/net/core/rmem_default • Overflow of fragmented packages • Turning Off Autonegotiation of NICs and Hubs
Security and NFS • Mount access • Achieved by client machine • Provided in /etc/exports file • File access • Function of normal file system access controls • After mounting, user and group permissions of files take control • Entries in /etc/hosts.allow and /etc/hosts.deny
Security and NFS (Contd) • Server security : nfsd and mountd • Use root_squash in /etc/exports /home slave1(rw,root_squash) • Client security • nosuid • broken_suid mount option • Securing portmapper, rpc.statd and rpc.lockd on client