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Backups

• Part of a Systems Administrators job is maintaining the integrity of the system. This does not mean that she is expected to prevent anything unexpected from happening ever. It just means that she needs to be aware of possible emergencies and have a plan to deal with them.

• One of the most basic emergencies is loss of data. In the event that the building burns down or a hard-drive goes bad or data is lost by the command rm *, the system can be rebuild, but without a backup, it cannot be restored to its original condition.

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Planning for Disasters and Everyday Needs

• There are many factors to consider in developing a backup plan :– What files need to be backed up?– Where are the files that need to be backed up?– Who will back up these files?– When, where and under what conditions should these

backups be performed?– How often do these files change?– How quickly does a missing file need to be restored?– Where will the data be restored?

• The ultimate goal is the ability to restore the entire system in a reasonable amount of time.

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Characteristics of a Good Backup Strategy

• Backup strategies change from site to site. There are a number of strategies that need to be considered when creating a backup plan.– Ease of use– time efficiency– ease if restoring files– ability to verify backups– tolerance of faulty media– portability to a range of machines

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Considerations for a Backup Strategy

• Other factors that may affect the type of backup strategy implemented are:– available commands– available hardware– maximum expected size of file systems– importance of data– level of data modification

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Scheduling Backups

• Depending on the requirements, an appropriate backup schedule needs to be defined.

• The simplest and most through backup scheme is to copy all the files on a system to a tape. This is called a full backup.

• Incremental backups are done more often than full backups. An incremental creates a copy of all the files that have changed since a previous backup.

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Backup Strategy

• Some files like /tmp may never need to be backed up. All dynamic files on the system should be backed up. These include:– Password and group files– Accounting files– Configuration files– Network files such as - localhosts, networks, route,

hosts.equiv– UUCP files such as - devices, dialers, L-devices– Cron files– User files

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Methods of Backup

• There are generally two ways that information can be transported from one media to another.– Image transports: This bypasses the file system and reads

the information straight off the disk using the raw device file. dd and dump uses this method.

– File by file: Stores files, one file at a time. It is more portable and is easier to restore. However, it is more time consuming to do. tar and cpio use this method.

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Backup Storage Consideration

• Properly storing the backup tapes, diskettes or other media once they are done is an important part of any backup plan.– Know where things are– Make routine restoration easy. (label and store close )– Write-protect backup media– Environmental considerations– Handle media properly– Take security into account– Figure out long-term storage