RH030 Linux Computing Essentials

1. RH030 Linux Computing Essentials Workbook 5 - Part 2 The Linux Filesystem

2. Objectives chapter 1 - 5 • Last week we looked at: • How the linux filesystem works • Filesystem structures • dentries, inodes, data blocks • ls -i • ls –s • Linking items – hard & soft links • ln • ln –s • Recognising the types of items found in the filesystem • regular files, directories, and symbolic links. • block and character device nodes. • mount • df Linux+ Guide to Linux Certification, 2e

3. Objectives chapter 5 - 7 • THIS WEEK • Searching for files and directories • Compressing Items • Archiving Items Linux+ Guide to Linux Certification, 2e

4. Command Covered • Review - locating information about files and directories • whereis, which, whatis, • Searching for files and directories • locate, find • Compressing Items • gzip bzip2 • Archiving Items • tar Linux+ Guide to Linux Certification, 2e

5. Files and Directories • You can locate information about files using various commands. • Such as locate, whereis, which, whatis and find • which command: • Used only on executable files • Lists the directory location on the system where the executable file is located. • Searches through the System Variable $PATH to see if this location is on it. • $PATH allows executable files to be run without specifying absolute or relative path • whereis command: • Used to locate the binary, source and man pages for a command. • whatis command: • Display’s 1st line of the man pages Linux+ Guide to Linux Certification, 2e

6. Locating the pathnames of items in FSH. • You can use any “text” to display any items which match to anything on any of the systems pathnames . • locate <item>: • Will search for anything within the system FSH pathname structure • Search identifies and displays all FSH pathnames which match to the text. • Shortcut to the slocate command • Uses an indexed database of all files on system • As the Information returned may not fit on screen it is commonly used the less / more commonds Linux+ Guide to Linux Certification, 2e

7. find command • It is one of the commands that everyone should master especially system administrators. • The first, and most obvious, use is find's ability to locate old, big, or unused files, or files that you just forgot where they are. • The other important characteristic is find's ability to automatically travel recursively down through subdirectories. • There are only a few unix commands which can be given a directory name and will automatically search down the directory pathname tree structure, searching each subdirectories. • The commands chmod, chgrp, rm, ls and cp will do it as well. But only if the -r or -R option is specified. • But the find command does this automatically. Linux+ Guide to Linux Certification, 2e

8. Syntax of the ‘Find Command’ find [starting pathname] [search criteria] [filename] [action] • [starting pathname] • The first argument of the findcommandis the location from which to start the search • This pathname tells the command in which directory to start searching. • In the starting pathname you can make use of any of any of the relative symbol characters using relative addressing. • Such as ~ .. . • [search criteria] • The search criteria options after the starting pathname always start with a minus sign, and give the criteria for the actual search. • [filename] • The filename is the item or items which will be searched for. • [action] • Optional action which you want to execute on the items you find. Linux+ Guide to Linux Certification, 2e

9. Using search criteria • You can nominate different search criteria to be used during the search • Such as can use the find command with “ –name “ to create a search which will list all files which start with the word chapter*. find ~ -name “chapter*?” OR find ~ -type d “bean??” Common criteria used with find command Linux+ Guide to Linux Certification, 2e

10. Combining search criteria • Creating multiple search criteria in one search. • example 1 • 1st – it searchs for items that end in name = “*chapter” • 2nd – further filters the search to find only files NOT directories find ~ - name “*chapter” - type f -group 100 • example 2 • The –not is a negative statement to tell NOT to look group 100. find ~ - name “*chapter” - type f - not -group 100 • example 3 • The 2>/dev/null serves to "throw away" complaints about directories which you do not have permissions to access. find /etc -size +200k 2>/dev/null Linux+ Guide to Linux Certification, 2e

11. Examples • A simple example of find is using it to list the names of all of the files in the nominated directory and all it’s subdirectories. • This is done with the simple commandfind . –name ‘*’ find ~ -name beans find ~ -name “bean??” find /usr/local -name share -type d find /etc -name fstab -type f find /home –type d –user root find . -name “*backups” -type d -user 504 find ~ -name “*chapter” -type f -group 100 Linux+ Guide to Linux Certification, 2e

12. Using -exec to execute actions • -exec, and its close cousin -ok. • The -exec mechanism is powerful: rather than just printing the names of matching files, secondary commands can be run. • But using the -exec is awkward because the syntax for specifying the command to run is tricky. • Syntax rules • The secondary command should be written after the -exec switch, • using a literal { } as a placeholder for the file name. • The command should be terminated with a literal ; • But as the ;has special significance to the shell, it must be "escaped" by a precending \. • An example will help clarify the syntax. find /etc -size +200k -exec cp { } /tmp/big \; Linux+ Guide to Linux Certification, 2e

13. SUMMARY OF SEARCH / LOCATE COMMANDS • locatecommand: Searches FSH pathname structure for anything which matchs. • whatis command: Display’s 1st line of the man pages • whereis command: Used to locate the binary, source & man pages for a command. • which command: • Used only on executable files • Lists the directory location on the system where the executable file is located. • Searches through the System Variable $PATH to see if this location is on it. • $PATH allows executable files to be run without specifying absolute or relative path • find command: • Used to locate particular items. • Able to modify searchs with use of selected criteria. • Able to recursively search thru nominated sections of FSH • Able to execute an action on located items. Linux+ Guide to Linux Certification, 2e

14. Next • Chapter 6 • Understanding compressed files • Creating compressed files • Viewing compressed files • Extracting compress files • Chapter 7 • Working with archived or backup files • Creating backup files • Viewing backup files • Extracting backup files Linux+ Guide to Linux Certification, 2e

15. Why use Compression? • Why do we use compression utilities? • Because the Internet only uses compressed files. • Files which are backed up onto another media using a backup utility are also commonly compressed to save space. • Tape devices are the default medium used for archives • Two most common compression utilities: • gzip • Bzip2 • Many compression utilities are available for Linux systems. • Each uses a different compression algorithm • That produces a different compression ratio. Linux+ Guide to Linux Certification, 2e

16. The gzip utility • gzip command: • A GNU utility • Most commonly utility used to compress files. • Used frequently utility for compressed files on the internet. • Adds the .gz filename extension by default • - l Used to display the level of compression achieved. • - v Used to display the level of compression achieved and display a list of the items which have been compressed. • gunzip command: • Used to decompress .gz files Linux+ Guide to Linux Certification, 2e

17. The bzip2Utility • bzip2 command: • Adds the .bz2 filename extension by default • Not as commonly used but still used a lot on the internet. • Because it typically yields better compression than gzip. • Used to compress files only • Cannot compress a directory full of files • bunzip2 command: • Used to decompress files compressed via bzip2 Linux+ Guide to Linux Certification, 2e

18. How compression works List the file to see the original size $ ls -l bin.file -rw-r--r-- 1 user2 staff 57380 Mar 22 09:17 bin.file Compress the file $ gzip -l bin.file bin.file: compression: 53.81% -- replaced with bin.file.gz List the file to see compressed size $ ls -l bin.file.gz -rw-r--r-- 1 user2 staff 26500 Mar 22 09:17 bin.file.gz Uncompress the file and list again $ gunzip -l bin.file.gz bin.file.gz: -- replaced with bin.file $ ls -l bin.file -rw-r--r-- 1 user2 staff 57380 Mar 22 09:17 bin.file Linux+ Guide to Linux Certification, 2e

19. Archiving files to create System Backups • Backups: • The Process whereby files are copied to an archive file. • The actual backup copies of directories & files are called archives. • Typically created by a backup utility. • Performing System Backups: • You should always backup any important system configuration files. • Plus the user files from their home directories. • Also possibly files used by system services, as well. Media: • They can be created on various media. • They can be created in various locations. • Default media has been tape. • But most popular media now is hardrives, CD’s & DVD’s • Several backup utilities available: • tar, cpio, dump/restore, burning software Linux+ Guide to Linux Certification, 2e

20. tar archive files (tarballs) • The tar ( “Tape Archive” ) command • It is still one of the oldest & most commonly used backup utilities. • It allows for the backing up of multiple files or directories in the file system. • It makes a single archive file out of the input files it backed up for extraction later. • Used extensively for files on the internet • These compressed archived files are called tarballs. • You should always add a .tar filename extension to identify it as a tarfile. • Files are not automatically compressed as they are archived. • Adding a – z will compresses them with gzip. • It adds the .tar.gz filename extension or .tgz filename extension Linux+ Guide to Linux Certification, 2e

21. The tar utility options • The tar syntax • tar function modifier destination.tar sourcefiles Linux+ Guide to Linux Certification, 2e

22. Maintaining Context • By default it always will change the ownership to who ever runs the command and reset the items with default permissions. • Using – pstops this. • It will keep existing ownership and group attributes • And stop it striping the ACL’s so it ignores umask and keeps the existing permissions tar cvfp net.tar /etc/sysconfig/networking Maintaining Pathnames • By default it always stores items using a relative pathname. • Using – Pstops this. • It stop it striping the leading “/” from the existing pathname. tar cvfP net.tar /etc/sysconfig/networking Linux+ Guide to Linux Certification, 2e

23. Maintaining Pathnames & Context • By default it always stores items using a relative pathname. • Adding a – Pstops this. • Sit sop it striping the leading “/” from the pathname. tar cvfP net.tar /etc/sysconfig/networking • Establishing Context. • the -C switch can also be used to help establish or maintain context of multiple items in the filesystem. • By changing directory before the archive is constructed. tar cvf net.tar -C /etc/sysconfig file1 file 2 -C /var/logs file 1 file 2 Linux+ Guide to Linux Certification, 2e

24. The tar ( Tape Archive) utility • Can create archive in a file on a filesystem or directly onto a device. • Defaults to tapedrive unless told to output to file onto a harddrive. • You use – f to modify this default and use another device such as the hardrive. Table 12-4: Common tape device files Linux+ Guide to Linux Certification, 2e

25. Options used with the tar utility Table 12-5: Common options used with the tar utility Linux+ Guide to Linux Certification, 2e

26. Options used with the tar utility Table 12-5 (continued): Common options used with the tar utility Linux+ Guide to Linux Certification, 2e

27. Example 1 1. archive a file $ tar cvf dir1files.tar dir1 2. list contents $ tar tvf dir1files.tar 3. remove dir1 and verify $ rm -r dir1 $ ls 4. extract the archived dir1 to your current directory $ tar xvf dir1files.tar Linux+ Guide to Linux Certification, 2e

28. Example 2 1. compress & archive a file $ tar cvfz dir1files.tar dir1 2. list contents $ tar tvfz dir1files.tar 3. remove dir1 and verify $ rm -r dir1 $ ls 4. extract the archived dir1 to your current directory $ tar xvfz dir1files.tar Linux+ Guide to Linux Certification, 2e

29. Workbook5 - Command Summary • ls – n –i –s • stats • ln –s • mount umount • mkfs df • locate, which, whereis, whatis • find • gzip bzip2 • tar Linux+ Guide to Linux Certification, 2e