Module 7 Archiving and Compression

1. Module 7Archiving and Compression

2. Exam Objective3.1 Archiving Files on the Command Line Objective Summary • Using archiving and compression with files and directories

3. Archiving and Compression

4. Archiving vs. Compression • Archiving collapses multiple files into one • A few files or multiple directories • Compression makes a file smaller • Remove redundant information, replace with a smaller code • Can be applied to individual files, groups of files or entire directory trees

5. Uses of Archiving and Compression • Managing log files • Sharing groups of files • Project documents • Source code • Compressing for more efficient transfer • Less data to send over the Internet or to tape • Keep like files together grouped by time • Backups

6. Lossless vsLossy Compression Lossless: • Decompressed file is the same as the original • Doesn’t compress as well as lossy • For data you want to preserve • Logs, documents, binaries, configuration Lossy: • Decompressed file might have lost information from the original • Drops “unimportant” information from the file to make it compress better • Images, sound, movies

7. gzipvs bzip2 • gzip and gunzip • Uses Lempel-Ziv coding • Lossless compression, good efficiency • Bzip2 and bunzip2 • Burrows-Wheeler block sorting • Lossless compression, slightly more efficient than gzip, but requires more CPU • Used almost identically as gzip

8. Using gzip/gunzip/bzip2/bunzip2 gzip foo # removes foo; creates foo.gz gunzipfoo.gz # removes foo.gz; creates foo gunzip –l foo.gz # shows statistics bzip2 foo # removes foo; creates foo.bz2 bunzip2 foo.bz2 bunzip2 –l foo.bz2 # DOESN’T EXIST!

9. Tape Archive - TAR tar –cffoo.tar * # create tar –tffoo.tar # show info tar –xffoo.tar # extract tar –czffoo.tgz * # gzip tar –xjffoo.tbz # bunzip2 tar –xffoo.tar home/joe # only extract home/joe

10. ZIP zip output.zip file1 file2 file3 zip foo.zipfile.doc # One file zip –r foo.zip Documents # recurse unzip –l foo.zip # show contents unzip foo.zip # extract all unzip foo.zip file1 # just file 1 unzip foo.zip Documents/projectA/* # everything under Documents/projectA