When and How Should I Back up My System?

Question: When and how should I back up my system?

Answer: (Date: 10/31/96: Revision: B.02.xx)

This describes some resources and processes that may help you improve or initiate your backup process, and references so that you can learn more about doing backups.

Section 1 - Important Notices Regarding Backups

1. First and most importantly, you should be doing regular backups of your system.

2. There is a known problem on HP3070 systems, Software Revision B.02.00 and beyond, with mkrs. The process to create the tape is unreliable, and you may wind up with a tape that is not bootable. (In other words, you might not be able to use the tape that mkrs creates.) The information in the System Administration and Networking Guide (Revision B), p. 10 is out of date.

   If you need to recover a system, please use the system install procedure, and then restore all your data files from your most recent backup. In general, you should use theinformation in Section 2 of the Software Update and Restoration Procedure for B.02.50, or the same section in the Software Installation Procedure for B.02.00. Since data on the disk is destroyed when you do the restoration, you will always need to do backups to keep up with changes in data on your system. The mkrs program (or any recovery program) only records a minimum set of files, not your whole system.

   If you need general information on backups, please see Section 2 in this document.

3. We recommend that you go to single user state before beginning a backup.

   Backups should be done when files on a system are not being changed. If you back up a system while programs are being run (for example, while boards are being tested), you will back up files that should only be there temporarily, and you will only get incomplete copies of files that are being written at the time of backup. You may get errors at the end of every backup, because the fbackup program is able to tell that files are different. It will issue errors on these files, and you can easily miss something important in between the less important errors.

4. Only use a tape for about 100 backups before replacing it; tapes do wear out.

Section 2 - Resources to help you learn

The HP-UX manuals that come with your system are another good resource. The book titled System Administration Tasks has a full chapter (Chapter 9) on "Backing Upand Restoring Your Data". This covers the programs fbackup, frecover, and SAM.

In addition to this, a variety of books are available at technical bookstores. Two that we've found useful are:

1. The HP-UX System Administrator's Handbook by Marty Poniatowski specifically addresses administering HP-UX systems, and has a good discussion of how fbackup, frecover, and SAM work together. There is a version of this book out for the 10.0 version of HP-UX, so please be careful which version you get. The HP3070 currently uses HP-UX 9.0.
2. UNIX for Dummies by John R. Levine and Margaret Levine Young - This book is written in a light, humorous style, with quite a bit of idiomatic English, but nevertheless is a good reference for general UNIX information. This book does not contain information specifically on HP-UX, but does contain a good discussion of how to decide what parts of your system to back up, and how often it will need to be backed up.

Section 3 - Terms and Definitions:

 

backup

The process of saving data from your disk to a tape or floppy. You may do a full backup - which backs up all the files on your hard disk, or a partial backup, which backs up only a selected set of files. Please look in both your HP3070 System Administration and Networking Guide or UNIX System Administration Tasks manual if you need details on the differences between different types of backups.

restore or recover

The process of getting your data back from a tape or floppy to your disk, usually after you have corrupted or missing files on your disk. You will only be able to recover data that you have previously saved in a backup. If you only need a few files from a backup tape, this is usually possible. Please see your HP3070 System Administration and Networking Guide or UNIX System Administration Tasksmanual if you need details on recovering files from backups.

nfs

Stands for "Network File System". An "nfs disk" is a disk that isn't physically part of your computer, but looks as though it is for most operations. It is actually physically part of another computer.

remote

a remote device is a device (usually a disk or tape drive) that is actually mounted on another computer, but is accessible from your machine. You access it across the network.

host

a host computer is one that provides a service - a file system or a tape drive, for example, to other computers on the network.

 

local

a device that is on your computer, not on a machine elsewhere on the network.

SAM

The "System Administration Manager", the HP-UX program that is used to help manage system resources.

Section 4 - Backups when your system is part of a network

fbackup -0i / -f hostname:/dev/update.src

This assumes that you're on the computer that needs to be backed up, and are sending the files to a tape drive on another machine (in the example above, this machine is named "hostname"). It also assumes a full backup. For more information on backing up and restoring over the network, please try typing:

man fbackup
man frecover

at the HP-UX prompt to learn more about these statements.

Do not run backups over nfs: the options you use on both fbackup and frecover are tricky, and you don't necessarily have the permissions you'd expect on remote disks. If you set up your backup incorrectly, it can be difficult or impossible to get the data back. If you must back up a disk that's nfs mounted to the system you're backing up, please consider doing a remote backup from this disk's host computer instead. Usually the only reason you'd want to do an nfs backup is when there is no tape drive on the host computer, making a remote backup necessary.

To find out if a disk is nfs-mounted, type "bdf" at a UNIX prompt. It will tell you if a disk is local (hfs) or nfs mounted. Here is an example:

 

$ bdf
Filesystem	kbytes	used	avail	capacity	Mounted on
/dev/dsk/0s0	1140518	1037324	46168	96%	/
/dev/dsk/cEd5s0	1213854	985271	216444	82%	/disk2
hpmtqc:/	1140518	1016188	67304	94%	/sys/hpmtqc
hpmman:/usr/frame	997678	876036	71758	92%	/usr/frame

The disks that you see on your system as "/" and "/disk2" are locally mounted; the disks that are named "/sys/hpmtqc " and "/usr/frame" are nfs mounted. You can see the difference because the nfs mounted disks have a hostname and then a colon in the "Filesystem" field.