![Networking: Name Resolution
Disabling Multicast DNS:
Edit Name Service Switch Configuration File
gksudo gedit /etc/nsswitch.conf
Find the “hosts” line:
hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
Remove the “mdns4” options:
hosts: files dns](https://image.slidesharecdn.com/ubuntuforbeginners-150701113731-lva1-app6891/85/Ubuntu-for-beginners-46-320.jpg)
Ubuntu for beginners
- 3. Boot Ubuntu from CD/DVD or USB ● Plug in the USB device (if booting from USB) ● Power on the computer ● “F12 Boot Options” — Press the F12 key ● “Preparing one-time boot menu...” — Wait ● Insert the CD/DVD (if booting from CD/DVD) ● Select your boot device from the list: o USB Storage Device o CD/DVD/CD-RW Drive ● Press the ENTER key...
- 4. Boot Ubuntu from CD/DVD or USB Press any key to select Language and Keyboard Layout
- 5. What is Ubuntu ? is a Linux distribution based on and derived from
- 6. What is Ubuntu ? was launched on October 20, 2004: Ubuntu 4.10, the Warty Warthog (“warty”)
- 7. What is Ubuntu ? is sponsored by Canonical Ltd. with Mark Shuttleworth as its CEO
- 8. What is Linux ? Depends on who you ask ! Steve Ballmer: “Linux is a cancer” —Chicago Sun Times, June 1, 2001
- 9. What is Linux ? Depends on who you ask ! Linus Torvalds: “I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones.” —comp.os.minix, August 26, 1991 “It is NOT protable (uses 386 task switching etc), and it probably never will support anything other than AT-harddisks, as that's all I have :-(”
- 10. What is Linux ? Depends on who you ask ! “GNU/Linux is a Free-as-in-Speech Operating System” GNU (“GNU is Not Unix”) is a Free Software Project to implement a UNIX-like Operating System, distributed under the GPL (“GNU General Public License”). However, the project got delayed for lack of a kernel. Eventually, the project decided to use the Linux kernel—hence, the GNU/Linux Operating System.
- 11. What is a Linux Distribution ? Linux Distribution (a.k.a. “distro”) = GNU Project Software + Linux Kernel + Further software selected by distro maintainer ⇨ Complete Operating System DistroWatch Distro Database Summary: ● Total number of distributions in the database: 761 ● Number of active distributions in the database: 304
- 12. What is Debian ? ● One of the most popular Linux distributions ● Founded by Ian Murdock on August 16, 1993 ● Named after Deb(by) + Ian ● Developed by over 3000 volunteers ● Considered exceptionally stable ● Great Software Package Management ● Used as a base for many other distributions
- 13. What is Debian ? A few distros derived from Debian: ● Damn Small Linux — 50-MB Live CD/DVD ● KNOPPIX — Live CD/DVD distribution ● LiMux — City Council of Munich, Germany ● Linex — Government of Extramadura, Spain ● … etc. … ● … and, of course: Ubuntu...
- 14. Debian Release History 1.1 buzz June 17, 1996 1.2 rex December 12, 1996 1.3 bo June 2, 1997 2.0 hamm July 24, 1998 2.1 slink March 19, 1999 2.2 potato August 15, 2000 3.0 woody July 19, 2002 3.1 sarge June 6, 2005 4.0 etch April 8, 2007 5.0 lenny February 14, 2009 6.0 squeeze February 6, 2011 7.0 7.1 wheezy May 4, 2013 June 15, 2013 Very long release cycle triggered Ubuntu project ◄ Code names of Debian releases are names of characters from the film “Toy Story.”
- 15. Ubuntu Release History 4.10 Warty Warthog October 20, 2004 5.04 Hoary Hedgehog April 8, 2005 5.10 Breezy Badger October 12, 2005 6.06 LTS Dapper Drake June 1, 2006 6.10 Edgy Eft October 26, 2006 7.04 Feisty Fawn April 19, 2007 7.10 Gutsy Gibbon October 18, 2007 8.04 LTS Hardy Heron April 24, 2008 8.10 Intrepid Ibex October 30, 2008 9.04 Jaunty Jackalope April 23, 2009 9.10 Karmic Koala October 29, 2009 10.04 LTS Lucid Lynx April 29, 2010 10.10 Maverick Meerkat October 10, 2010 (10.10.10, at 10:10 UTC) 11.04 Natty Narwhal April 28, 2011 11.10 Oneiric Ocelot October 13, 2011 12.04 LTS Precise Pangolin April 26, 2012 12.10 Quantal Quetzal October 18, 2012 13.04 Raring Ringtail April 25, 2013 ◄ 18-month support ◄ 5-year server support 3-year desktop support ◄ 5-year support ◄ 9-month support Code names of Ubuntu releases are “Adjective Animal”—alphabetical since 5.10
- 16. ““Unity”Unity” The Ubuntu Desktop:The Ubuntu Desktop:
- 17. Dash
- 18. Dash Home
- 20. Networking If ethernet cable is not plugged in: If driver for wireless interface is available:
- 23. Wireless Network Authentication Click “Ignore”. The system should connect to the selected wireless network.
- 24. Starting the Command-Line Shell Click Dash Home: Type “terminal”: Click “Terminal” icon:
- 25. File System Layout ● No drive letters ● One directory hierarchy ● One main directory: – Called the root directory – Denoted with a slash (“/”) ● Multiple disk partitions or devices: – “Mounted” to a directory
- 26. File System Layout Listing Directory Contents—the “ls” command: ls / Option “-1”—List one entry per line: ls -1 / Option “-l”—Use long listing format: ls -l /
- 27. File System Layout ● “/root” — Home directory for “root” user account ● “/home” — Home directories for other users ● “/boot” — Boot loader ● “/dev” — Device nodes ● “/etc” — System configuration files ● “/mnt” — Manual mount points ● “/media” — Automatic mount points Important top-level directories:
- 28. File System Layout ● “/bin” — Essential user programs ● “/lib” — Essential system libraries ● “/sbin” — System programs (system boot process, “root” user) ● “/usr” — User programs, docs, libs, headers, … ● “/opt” — Optional software packages ● “/var” — Log files, cached data, lock files, … ● “/tmp” — Temporary files ● “/proc” — Kernel information as virtual files Important top-level directories (cont'd):
- 29. Online Manual Pages Online manual pages—the “man” command: man ls The “man” command has a manual page, too: man man Where are the manual pages to be found? manpath
- 30. Current Working Directory Display current directory—the “pwd” command: pwd Change current directory—the “cd” command: cd DIRECTORY Change current directory to home location: cd
- 31. Who Am I—User Accounts Display username—the “whoami” command: whoami Display user account—the “id” command: id List all user accounts—the “/etc/passwd” file: cat /etc/passwd
- 32. Who Am I—User Accounts Using a pager to display the user accounts: more /etc/passwd But—“less” is “more” (more or less): less /etc/passwd List only the account names: cut -d ':' -f 1 /etc/passwd | less
- 33. Who Am I—User Accounts Every user account is a member of one or more groups—cf. the “id” command: id List all groups: less /etc/group “GID” is the primary group.
- 34. The “root” User Account The “root” user account: id root grep '^root:' /etc/passwd ● Is the almighty “superuser”; ● Is used for system administration tasks; ● Has user id 0; ● Is disabled by default on Ubuntu.
- 35. Obtaining root Privileges (“becoming root”) If the root user account is enabled: su - Requires knowledge of the root password. Type “exit” to relinquish root privileges. If the “root” user account is disabled: sudo COMMAND-TO-RUN-AS-ROOT Requires “sudoer” rights. Runs a single command as root.
- 36. Obtaining root Privileges (“becoming root”) But I hate typing “sudo” over and over again! sudo su - Still requires “sudoer” rights. Type “exit” to relinquish root privileges. A little experiment: whoami sudo su – whoami exit whoami
- 37. File Permissions File permissions are included in “ls -l” output: drwxrwxrwx -rwxr-xr-x “Other” Access Rights “User” Access Rights “Group” Access Rights Filesystem Object Type
- 38. File Permissions Common Filesystem Object Types: - Regular File d Directory l Symbolic Link c Character Device (unbuffered) b Block Device (buffered)
- 39. File Permissions Access Permissions: r 4 Permit reading the file Permit listing the directory contents w 2 Permit writing to the file Permit adding, removing, renaming files in directory x 1 Permit executing the file Permit entering the directory and using its contents Note: If you have “Execute-only” permission on a directory, then you can access its contents only directly by name.
- 40. File Permissions Changing permissions—the “chmod” command: chmod 754 PATH “User” gets 7 (read + write + execute). “Group” gets 5 (read + execute). “Other” gets 4 (read). chmod go+w,a-x PATH Add write for “Group” and “Other”. Remove execute for all. Note: “a” is synonymous with “ugo”.
- 41. Mounting External Media (e.g., USB disk, CD-ROM, …) Simply plug in the device, or insert the disc ⇒ The medium will automatically be mounted ⇒ An icon will appear in the Dash ls -l /media The device will appear in the “/media” directory: The device will be listed by the “mount” command: mount
- 42. Mounting Fixed Disk Partitions Open the File Manager (“Nautilus”) from the Dash and click the disk volume that you want to use ⇒ The medium will automatically be mounted ⇒ An icon will appear in the Dash ls -l /media The device will appear in the “/media” directory: The device will be listed by the “mount” command: mount
- 43. Mounting from the Command Line E.g., a CIFS share: mkdir Digipolis sudo mount -t cifs //antwerpen.local/digipolis/klanten Digipolis -o username=RCxxxxx@ICA But beware of name resolution issues: ping antwerpen.local
- 44. Networking: Name Resolution Name resolution—the “nslookup” command: nslookup digipolis.be nslookup antwerpen.local Name resolution—the “getent” command: getent hosts digipolis.be getent hosts antwerpen.local getent ahosts digipolis.be getent ahosts antwerpen.local
- 45. Networking: Name Resolution Ubuntu enables Multicast DNS by default: getent hosts $(hostname).local getent ahosts $(hostname).local Run the “hostname” command and substitute its output into the command line
- 46. Networking: Name Resolution Disabling Multicast DNS: Edit Name Service Switch Configuration File gksudo gedit /etc/nsswitch.conf Find the “hosts” line: hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4 Remove the “mdns4” options: hosts: files dns