Backup & Recovery: Inexpensive Backup Solutions for Open Systems

4.3. Backing Up Clients via NFS or Samba

Compared to the traditional approach of using an Amanda client on the system to be protected, there are several advantages of backing up via the Network File System (NFS) or Samba:^[]

^[] Samba is an open-source implementation of the SMB protocol, which is also called Common Internet File System (CIFS). SMB/CIFS is commonly used on Windows systems.

• You don't need to install and configure Amanda client software on the system to be protected. More systems can be added to the list of protected systems by modifying files on one system.

• A native Amanda client may not be available for a particular operating system. An NFS/SMB approach gives you the ability to back up such an operating system.

• You use significantly less CPU and memory resources on the protected system.

• If the important data from the protected systems is already available via NFS or CIFS, this approach provides better integration with the company IT policy.

However, consider the trade-offs of this approach:

• Think about the security issues of the mounting mechanism, whether SMB or NFS. You will not be able to use the mechanism provided by Amanda to encrypt the data in transit from the client to the server. You will also need to understand the security implications of running NFS or Samba on the system you want to protect in the first place. For example, if you do not want to run an NFS server all of the time on the system you want to back up, you will need to craft a synchronization scheme in which the NFS server on the system starts running just before the backup starts.

• Access privileges need to be carefully worked out. The Amanda server needs both read and write privileges on the NFS mount point. Read permission is necessary during the backup phase. Write permission is necessary during a restore.

• You will not be able to use local filesystem-based mechanisms for optimizing the backup process. For example, you will not be able to use dump or xfsdump on a filesystem being accessed over the network.

• You cannot back up any open files being accessed via Samba. You cannot back up extended file attributes via Samba.

4.3.1. Backing Up Using NFS

To back up using NFS, you need to install and configure an NFS server on the target system, and an NFS client on the Amanda server. At this point, export the filesystems to be backed up (by listing them in the /etc/exports file of the client system). Make sure that the Amanda server can access all the files that need to be backed up. In many cases, this means turning on the no_root_squash option on the NFS share being backed up so that the Amanda server can access all files. Note that the hostname in the corresponding disk list entry should be the system where the NFS share is being mounted (not the client system). For example, in the sample network in Figure 4-6, the hostname in the disk list entry would be Quartz.

4.3.2. Backing Up via Samba

To back up using Samba, install the Samba client on the Amanda server. You don't have to explicitly mount the remote filesystem. Amanda is well integrated with the smbclient utility (an ftp-like client that is used to access SMB/CIFS resources on servers). It uses the -T option to create tar-compatible backups of all the files on an SMB/CIFS share. Amanda clears the archive bit of the files on the Windows-based target it backs up, enabling the incremental backup process.

A user must be created on the Windows system with full access rights (read/write) to the share. (In the example network in Figure 4-7, the user is amandabackup.) Amanda connects to the share as this user. If the user does not have full access, incremental backups will not work, and the whole share will be backed up every time (because the archive bits are never reset). Note that if any other program on the Windows system resets the archive bit of a file, Amanda will not back up that file during an incremental backup.

In addition to the standard Amanda configuration, you need to create the file /etc/amandapass on the system running the smbclient utility. This file contains authentication information to access specific Windows shares. Also note that the hostname in the corresponding disk list entry refers to the system running smbclient, not the Windows system being backed up. In Figure 4-7, it would be Amanda server Quartz.

Many Amanda installations protect Windows servers and PCs in production. For example, the Radiology Department at a large Midwestern university has been using Amanda since 1999. In the past, their Amanda server ran on IRIX, AIX, and Solaris, but the current Amanda server runs on Linux with indices replicated to another server. They back up more than 70 Linux, Solaris, IRIX, Mac OS X, and Windows clients with around 4 TB of backup data. The holding disk is 1.4 TB, and the dump cycle is 90 days. All Windows clients are protected using Samba. Several times per month, they recover files because of user error or hard-drive failures and have never lost data because Amanda was always able to recover lost files. The next section describes Amanda recovery.