Pokrewne
- Strona Główna
- McGraw.Hill,.Digital.Animation.Bible.Creating.Professional.Animation.with.3ds.Max.Lightwave.and.Maya.(2004).LiB
- Linux administracja sieciami zaawansowane ( 554 strony )
- Sams' Teach Yourself Linux In 24 Hours
- Teach yourself linux in 24 hours
- 100 linux tips and tricks
- linux podrecznik administratora (PL) (2)
- !!linux podrecznik administratora (PL)
- Anne McCaffrey Jezdzcy Smokow Niebiosa Pern
- Sheldon Sidney Gdy nadejdzie jutro (2)
- Long Julie Anne Siostry Holt 02 Urocza i nieznoÂśna
- zanotowane.pl
- doc.pisz.pl
- pdf.pisz.pl
- cukrzycowo.xlx.pl
[ Pobierz całość w formacie PDF ]
.And they control the start-up of most daemons and server processes atboot time.The init daemon and its configuration file, /etc/inittab, also factor heavily in the initial start-up of your RedHat Linux system.They implement the concept of run levels that is carried out by the shell scripts in/etc/rc.d/init.d, and they provide a means by which the machine can be shut down or rebooted in an orderlymanner.To have shell scripts configured to run on an ongoing basis, you can use the cron facility.Cron jobs can beadded by editing cron files directly or by running commands such as at and batch to enter the commands to berun. Chapter 13: Backing Up and Restoring FilesOverviewIf you've ever suffered a hard drive crash, you know just how aggravating it can be.Irreplaceable data can belost.Countless hours may be spent reinstalling your operating system and applications.It is not a funexperience.It need happen only once for you to learn the importance of making regular backups of yourcritical data.Today, larger and faster backup media can help simplify the process of backing up your data.Red Hat Linuxsupports many different types of media such as writable CD-ROM and magnetic tape for creatingbackups.Using tools such as cron, you can configure backups to run unattended at scheduled times.This chapter describes how to create a backup strategy and how to select media for backing up data on yourRed Hat Linux system.It tells how to do automated backups and backups over a network.It also describeshow to restore individual files, or entire file systems, using tools such as the restore command.Selecting a Backup StrategyThere are several approaches to backing up your data.You need to ask yourself a few questions to decidewhich approach is best for you.Some things that you should consider are:"In the event of a crash, how much downtime can I tolerate?"Will I ever need to recover older versions of my files, or is just the most recent revision sufficient?"Do I need to back up files for just one computer or for many computers on a network?Your answers to these questions will help you decide how often to do full backups and how often to doincremental backups.If the data is particularly critical, you may even decide that you need to have your dataduplicated constantly, using a technique called disk mirroring.The following sections describe differentbackup methods.Full backupA full backup is one that stores every file on a particular disk or partition.If that disk should ever crash, youcan rebuild your system by restoring the entire backup to a new disk.Whatever backup strategy you decideon, some sort of full backup should be part of it.You may perform full backups every night or perhaps onlyonce every week; it depends on how often you add or modify files on your system, as well as the capacity ofyour backup equipment.Incremental backupAn incremental backup is one that contains only those files that have been added or modified since the lasttime a more complete backup was made.You may choose to do incremental backups to conserve your backupmedia.Incremental backups also take less time to complete.This can be important when systems are in highuse during the work week and running a full backup would degrade system performance.Full backups can bereserved for the weekend when the system is not in use. Disk mirroringFull and incremental backups can take time to restore, and sometimes you just can't afford that downtime.Byduplicating your operating system and data on an additional hard drive, you can greatly increase the speedwith which you can recover from a server crash.With disk mirroring, it is usually common for the system to continuously update the duplicate drive with themost current information.In fact, with a type of mirroring called RAID 1, the duplicate drive is written to atthe same time as the original, and if the main drive fails, the duplicate can immediately take over.This iscalled fault-tolerant behavior, which is a must if you are running a mission-critical server of some kind.Network backupAll of the preceding backup strategies can be performed over a network.This is good because you can share asingle backup device with many computers on a network.This is much cheaper and more convenient thaninstalling a tape drive or other backup device in every system on your network.If you have many computers,however, your backup device will require a lot of capacity.In such a case, you may consider a mechanicaltape loader or writable CD jukebox.It is even possible to do a form of disk mirroring over the network.For example, a Web server may store aduplicate copy of its data on another server.If the first server crashes, a simple TCP/IP hostname change canredirect the Web traffic to the second server.When the original server is rebuilt, it can recover all of its datafrom the backup server and be back in business.Selecting a Backup MediumArmed with a backup strategy in mind, it is time to select a backup medium.Several types of backuphardware and media are available for use with Red Hat Linux.Each type has its advantages anddisadvantages [ Pobierz całość w formacie PDF ]
zanotowane.pl doc.pisz.pl pdf.pisz.pl agnieszka90.opx.pl
.And they control the start-up of most daemons and server processes atboot time.The init daemon and its configuration file, /etc/inittab, also factor heavily in the initial start-up of your RedHat Linux system.They implement the concept of run levels that is carried out by the shell scripts in/etc/rc.d/init.d, and they provide a means by which the machine can be shut down or rebooted in an orderlymanner.To have shell scripts configured to run on an ongoing basis, you can use the cron facility.Cron jobs can beadded by editing cron files directly or by running commands such as at and batch to enter the commands to berun. Chapter 13: Backing Up and Restoring FilesOverviewIf you've ever suffered a hard drive crash, you know just how aggravating it can be.Irreplaceable data can belost.Countless hours may be spent reinstalling your operating system and applications.It is not a funexperience.It need happen only once for you to learn the importance of making regular backups of yourcritical data.Today, larger and faster backup media can help simplify the process of backing up your data.Red Hat Linuxsupports many different types of media such as writable CD-ROM and magnetic tape for creatingbackups.Using tools such as cron, you can configure backups to run unattended at scheduled times.This chapter describes how to create a backup strategy and how to select media for backing up data on yourRed Hat Linux system.It tells how to do automated backups and backups over a network.It also describeshow to restore individual files, or entire file systems, using tools such as the restore command.Selecting a Backup StrategyThere are several approaches to backing up your data.You need to ask yourself a few questions to decidewhich approach is best for you.Some things that you should consider are:"In the event of a crash, how much downtime can I tolerate?"Will I ever need to recover older versions of my files, or is just the most recent revision sufficient?"Do I need to back up files for just one computer or for many computers on a network?Your answers to these questions will help you decide how often to do full backups and how often to doincremental backups.If the data is particularly critical, you may even decide that you need to have your dataduplicated constantly, using a technique called disk mirroring.The following sections describe differentbackup methods.Full backupA full backup is one that stores every file on a particular disk or partition.If that disk should ever crash, youcan rebuild your system by restoring the entire backup to a new disk.Whatever backup strategy you decideon, some sort of full backup should be part of it.You may perform full backups every night or perhaps onlyonce every week; it depends on how often you add or modify files on your system, as well as the capacity ofyour backup equipment.Incremental backupAn incremental backup is one that contains only those files that have been added or modified since the lasttime a more complete backup was made.You may choose to do incremental backups to conserve your backupmedia.Incremental backups also take less time to complete.This can be important when systems are in highuse during the work week and running a full backup would degrade system performance.Full backups can bereserved for the weekend when the system is not in use. Disk mirroringFull and incremental backups can take time to restore, and sometimes you just can't afford that downtime.Byduplicating your operating system and data on an additional hard drive, you can greatly increase the speedwith which you can recover from a server crash.With disk mirroring, it is usually common for the system to continuously update the duplicate drive with themost current information.In fact, with a type of mirroring called RAID 1, the duplicate drive is written to atthe same time as the original, and if the main drive fails, the duplicate can immediately take over.This iscalled fault-tolerant behavior, which is a must if you are running a mission-critical server of some kind.Network backupAll of the preceding backup strategies can be performed over a network.This is good because you can share asingle backup device with many computers on a network.This is much cheaper and more convenient thaninstalling a tape drive or other backup device in every system on your network.If you have many computers,however, your backup device will require a lot of capacity.In such a case, you may consider a mechanicaltape loader or writable CD jukebox.It is even possible to do a form of disk mirroring over the network.For example, a Web server may store aduplicate copy of its data on another server.If the first server crashes, a simple TCP/IP hostname change canredirect the Web traffic to the second server.When the original server is rebuilt, it can recover all of its datafrom the backup server and be back in business.Selecting a Backup MediumArmed with a backup strategy in mind, it is time to select a backup medium.Several types of backuphardware and media are available for use with Red Hat Linux.Each type has its advantages anddisadvantages [ Pobierz całość w formacie PDF ]