4.8 apend backups
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This document discusses backups in Linux systems. It covers various tools for backing up files and directories like tar, rsync, burning software and tape drives. It explains how to create, view, extract tar archives and compress them using gzip or bzip2 to reduce file sizes. Key areas covered include what to backup, local and remote backup locations, and how backups are different for small and large systems. The document also provides a brief overview of zip files and their role in backups.
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What to backup
3
Backup for:
•Hardware failures
•Software failures
•[Epic] User failures
•Disasters
Backups
What to backup:
•At minimum, all user data and intellectual property
•At maximum, entire systems, OS and all
Factors for what gets backed up:
•budget
•time
•resources
•need](https://image.slidesharecdn.com/tjlkdt00q32wtre684g1-signature-b02a6c073768d8536fdd50c0a47af6292b168fbd705c8180447bb0b754b59738-poli-141223132216-conversion-gate02/85/4-8-apend-backups-3-320.jpg)
![CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012
Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed
Create and view tar archives
5
To create a tar archive: tar cf <tarfile.tar> <file> [file]...
•The c option tells tar to create an archive.
•The f option is critical - tells tar to put archive in a file on disk, rather than on tape device.
•You can add the v option (tar cvf) to get verbose output.
Tar will report every file added to the archive.
Backups
To view a tar archive (a table of contents): tar tf tarfile.tar
•The t option asks tar to print a table of contents of the archive.
•add the verbose flag (tvf), tar will report detailed info on each file, similar to ls –l cmd.](https://image.slidesharecdn.com/tjlkdt00q32wtre684g1-signature-b02a6c073768d8536fdd50c0a47af6292b168fbd705c8180447bb0b754b59738-poli-141223132216-conversion-gate02/85/4-8-apend-backups-5-320.jpg)
4.8 apend backups
- 2. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed Key Knowledge Areas Understand the correct way to backup with shell tools Backups Backups Terms and Utilities rsync, tar, burning software, tape drive rsync, tar, enterprise backup software, tape libraries 2
- 3. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed What to backup 3 Backup for: •Hardware failures •Software failures •[Epic] User failures •Disasters Backups What to backup: •At minimum, all user data and intellectual property •At maximum, entire systems, OS and all Factors for what gets backed up: •budget •time •resources •need
- 4. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed Where to backup and How 4 Backup to: •Local online copies •Remote online copies •Offline copies - Disk, Tape How to Backup: •Small scenario: rsync, tar, burning software, tape drive •Large scenario: rsync, tar, enterprise backup software, tape libraries Backups How to backup a directory? The directory represents an entire tree of files and directories? How can you put all of the information necessary to recreate the tree into one file? tar Originally the Tape Archive tool. Used to backup directory trees to tape. Nowadays more commonly used to “flatten” a tree into one file.
- 5. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed Create and view tar archives 5 To create a tar archive: tar cf <tarfile.tar> <file> [file]... •The c option tells tar to create an archive. •The f option is critical - tells tar to put archive in a file on disk, rather than on tape device. •You can add the v option (tar cvf) to get verbose output. Tar will report every file added to the archive. Backups To view a tar archive (a table of contents): tar tf tarfile.tar •The t option asks tar to print a table of contents of the archive. •add the verbose flag (tvf), tar will report detailed info on each file, similar to ls –l cmd.
- 6. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed extract tar archives 6 To Extract right requires understanding of how tar stores file in the archive. •When an archive is created, the pathnames are stored into the archive. •When you view the table of contents, you’re viewing the relative pathnames as they would be created on extraction. Backups Ex: • If tar tvf file.tar reports: memo.txt report/ report/data • Then when the archive is extracted, resulting files will be: CWD/memo.txt CWD/report/ CWD/report/data • Where CWD represents the current working directory To extract an archive: tar xf tarfile.tar •(careful) tarfile.tar will be extracted to the current working directory. •Understand contents of tar file to be sure you don’t accidentally overwrite existing files.
- 7. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed compress arquives 7 Tar files can get quite large, and storing/sharing them uncompressed wastes a large amount of storage space and bandwidth. Enter: compression. Compression uses complex algorithms to rewrite contents of a file in a way that takes up less space, and can be reversed back to original contents. Backups
- 8. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed Compression algorithms 8 BZIP2 - Powerful algorithm: Burrows-Wheeler Block Sorting Huffman Coding •Achieves 50-75% compression on average •Extension: .bz2 •Compress: bzip2 •Decompress: bunzip2 Backups One of the original compression algorithms: the Adaptive Lempel-Ziv. Not used very much any more, especially in Linux environment •Achieves 40-50% compression on average •Extension: .Z •Compress: compress •Decompress: decompress GZIP - Updated algorithm: Limpel-Ziv 77 ( LZ77 ) •Achieves 60-70% compression on average •Extension: .gz •Compress: gzip •Decompress: gunzip
- 9. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed tar + compression 9 Backups Once a tarball has been created, it’s generally compressed with gzip or bzip2 Ex: gzip -9 tarfile.tar bzip2 -9 tarfile.tar •The -9 option tells compression tool to maximize compression efficiency (taking longer). •1-9 are acceptable values, with -1 indicating minimal efficiency and maximum speed.
- 10. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed ZIP Files 10 Backups Zip files, originally put forward in DOS/Windows world via the pkzip tools, and now winzip, are actually a combination of hierarchy archiving and compression. zip files include features of tar and compression in one format. There are open source tools which allow access to creating, viewing and extracting zip files in the Linux environment. ZIP - Lots of algorithms implemented Varying compression ratio depending on algorithms used •Extension: .zip •Compress: zip •Decompress: unzip • zip files are not just compressed files. Archive contains files and directories within, so interface is closer to tar than gzip or bzip2. • Generally, zip files are only encountered in the Linux when interacting with Windows world. Within Linux, everything is a compressed tarball