Section 20.
File sharing.
"A
stateless protocol is one where each transaction is handled
separately; the server doesn’t need to keep
information about what clients have done previously. Being
stateless allows an NFS server to reboot while clients are
making requests and, once it returns to service, continue
serving files to clients as if nothing had
happened."
Zwicky, Cooper and Chapman - building Internet Firewalls, 2nd Edition.
20. File sharing in Linux.
The two most common tools for
sharing files between networked hosts (Windows, Linux, UNIX,
Apple and others) are NFS and Samba
(CIFS/SMB).
20.1. Network File System NFS.
NFS, the Network File
System was originally developed by Sun MicroSystems in
1984.
The current version of
NFS is v4. Version 4 is the first to be developed by
the Internet Engineering Task Force (INETF) after the
handover from Sun MicroSystems. NFS v4 is much
influenced by the Andrew Files System (AFS). It is stateful
and includes mandatory security features. (The original
NFS was designed to be "stateless" and was
implemented entirely in UDP).
In order to run NFS we need
remote procedure calls (RPC) and the NFS kernel
server (nfs-kernel-server).
In order to use NFS services we
need the nfs client (nfs-common).
Files can be directly exported
from the command line but more usually the exports are set
up in /etc/exports The command
exportfs -a
will export all the configured
files and can be run at boot time.
Issuing the command without any
flags will return a list of the currently exported files
together with the access controls.
20.2. Exercise.
Install both the NFS
server and client on your host.
Create a directory
/export/home and transfer your home directory to this
location.
Do an NFS mount of your
own directory back to /home/<username>
Try mounting your colleagues
home directories to your local host.
Read the section on using the
automounter (autofs), and configure the
automounter using /etc/auto.master and
/etc/auto.home to automount your own and your
colleagues home directories.
Read the manual pages on
NFS security settings, limiting host access,
exporting read only, root access etc. Modify your exports to
reflect your understanding of these settings.
20.3. Sharing with Windows - Using Samba.
Samba is a free open source
implementation of the Server Message Block (SMB), or
Common Internet File System (CIFS), that is used by
Microsoft Windows hosts.
Using the Samba server
Linux files and printers can be made available to Windows
desktop clients. The Samba client tools also make it
possible to read and write Microsoft shares.
Samba can provide authentication
services for windows hosts or can be configured to use
Windows authentication servers.
20.4. Exercise.
Set up Samba on your
local host.
Examine the file
/etc/samba/smb.conf and remove the # characters that
preceded the homes stanza.
Use the smbclient to
access your own home directory and those of colleagues on
other hosts in the training lab.
