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INFO 320 Server Technology I

INFO 320 Server Technology I. Week 9 Unix/Linux tools. Overview. This wraps up the course with a handful of other tools and technologies of interest Linux Utilities RAID. Linux Utilities. From notes by Dr. Randy M. Kaplan, and (Petersen, 2009). Linux Utilities.

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INFO 320 Server Technology I

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  1. INFO 320Server Technology I Week 9 Unix/Linux tools INFO 320 week 9

  2. Overview This wraps up the course with a handful of other tools and technologies of interest Linux Utilities RAID INFO 320 week 9

  3. Linux Utilities From notes by Dr. Randy M. Kaplan, and (Petersen, 2009) INFO 320 week 9

  4. Linux Utilities We’ll look at a few more Unix applications of common interest for server administration uniq, diff lpr, cups which, tar ntp, cron emacs INFO 320 week 9

  5. uniq uniq removes duplicate lines in a file uniq filename Example uniq lastnames Any duplicate names in the file named lastnames will be eliminated Make sure to sort the file first! INFO 320 week 9

  6. diff diff compares the contents of one file with another file diff filename1 filename2 Example diff colorsa colorsb Compares the contents of colorsa with the contents of colorb INFO 320 week 9

  7. diff The diff utility bears some further examination Let’s assume that colorsa contains – Red Blue Green Yellow Let’s assume that colorsb contains – Red Blue Green INFO 320 week 9

  8. diff The diff utility operates under the assumption the first file is to be converted into the second file diff output is a series of lines that define how the first file can be modified so that its content matches the second file The output for colorsa and colorsb would be 4d3 which specifies that the 4th line of the colorsa file should be deleted in order that the colorsa file match colorsb INFO 320 week 9

  9. lpr lpr prints a file lpr filename Example lpr areport lpr –PofficePrinter areport (prints the file areport on the printer named officePrinter) INFO 320 week 9

  10. cups The Common Unix Printing System (CUPS) is a GNU print server application Cups is managed using a web-based tool at http://localhost:631 There you can see print jobs, manage printers, etc. But first you need to define the printers to be managed INFO 320 week 9

  11. cups It config file is /etc/cups/printers.conf That contains the device file for each printer and configuration entries for it Devices can be identified by parallel name (lp0, lp1, …), serial name (tty0, tty1), or URI Each device gets a print spool directory under /var/spool/cups/devicename The cups daemon is cupsd INFO 320 week 9

  12. which which shows the location of the file related to the command (like whereis) which command Example which info /usr/local/bin/info Useful when a command is not doing what is expected INFO 320 week 9

  13. tar tar is short for ‘tape archive’ Original purpose was to create and read magnetic tape archives Today it’s used to extract a directory with subdirectories and files beneath it tar files are also frequently compressed The extension of a tar file that has been compressed will be .tar.gz or .tgz INFO 320 week 9

  14. tar tar syntax is tar options filename Example tar –xvzf myTarfile.tgz Decompress and restore (extract) all files in the archive named myTarfile.tgz INFO 320 week 9

  15. ntp The Network Time Protocol (ntp) coordinates time settings across your network It and its documentation (ntp-doc) are installed with apt-get or aptitude like most packages Docs are likely under /usr/share/doc/ntp-doc/html/index.html INFO 320 week 9

  16. ntp The ntp config file is /etc/ntp.conf Start ntp with sudo /etc/init.d/ntp start Check status of ntp with ntpq –p Or use an external ntp server with the ntpdate command (add to startup or cron) sudo ntpdate ntp.ubuntu.com INFO 320 week 9

  17. cron Addressed in more detail in connection with backups, cronallows you to schedule scripts to execute cron is started automatically from /etc/init.d on entering multi-user runlevels crontab files can be in its spool area (/var/spool/cron/crontabs) and more important (/etc/crontab)  this is where you define cron jobs! INFO 320 week 9

  18. cron cron logs its action to the syslog facility ’cron’, and logging may be controlled using the standard syslogd facility The heart of setting a service to run, is defining a crontab entry for it You can specify when a file runs by minute, hour, day of month, month, or day of week Each of those five parameters correspond to numbers or *s at the start of each entry INFO 320 week 9

  19. cron # use /bin/sh to run commands, no matter what /etc/passwd says SHELL=/bin/sh # mail any output to ‘bruce@example.com’, no matter whose crontab this is MAILTO=bruce@example.com # run five minutes after midnight, every day 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 INFO 320 week 9

  20. cron # # run at 2:15pm on the first of every month -- output mailed to bruce (above) 15 14 1 * * $HOME/bin/monthly 23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" 5 4 * * sun echo "run at 5 after 4 every sunday" INFO 320 week 9

  21. Editors Before there were word processors there were programs called editors Like a word processor, an editor is used to create text files and manipulate them The original use for a text editor was to create program files and modify them A venerable text editor, designed for Lisp programming, is Emacs INFO 320 week 9

  22. Emacs Not developed in the UNIX environment Therefore – not a special purpose utility More than a text editor Built-in programming language, Lisp Designed to do everything Emacs is a language sensitive editor with specific features for editing programming languages INFO 320 week 9

  23. The big pattern! Notice the pattern for most Unix applications outside of the kernel App names are all lower case, e.g. appname Most apps can be installed with apt-get or aptitude, e.g. sudo apt-get install appname Every app has a man page; man appname Most apps have a text configuration file, often something like /etc/appname.conf INFO 320 week 9

  24. The big pattern! Many apps can be started with sudo /etc/init.d/appname start If the app needs a spool directory, it’s under /var/spool/appname The daemon for an app is usually appnamed If there’s separate documentation for the app, it’s probably under /usr/share/doc/appname See? UNIX is easy! INFO 320 week 9

  25. RAID Mostly from (Bytepile, 2009) and (Rankin, 2009) Above image from www.fordcortina.net/pix/raid.jpg INFO 320 week 9

  26. RAID RAID (was Redundant Array of Inexpensive Disks, now often Independent) was developed circa 1988 by Patterson, Gibson & Katz; Berkeley CA A RAID array is a collection of drives which collectively act as a single storage system, which can tolerate the failure of a drive without losing data, and which can operate independently of each other. INFO 320 week 9

  27. RAID RAID is defined by various levels a set of disks (a RAID array) is designed to achieve – RAID 0, RAID 5, etc. They differ mainly in terms of Cost Speed Redundancy, and efficiency to do so How many disks are needed at a minimum INFO 320 week 9

  28. RAID RAID can be implemented in software alone, or with dedicated hardware (e.g. cards or built into a motherboard) Hardware-based RAID is faster and more expensive RAID typically requires all drives in an array to be identical (same make and model, not just same size and capacity) INFO 320 week 9

  29. RAID 0 RAID 0 is known as striping (watch spelling, it’s not stripping!) It offers no redundancy, but improves performance (speed) by reading alternately between disks No speed improvement for writing data! Two or more drives can do RAID 0 INFO 320 week 9

  30. RAID 1 RAID 1 is called mirroring It does nothing for performance, but provides redundancy by maintaining a duplicate copy of data Hence there is 100% duplication of data, the least efficient possible RAID Using at least two disks in matched pairs, it simply makes two copies of everything on separate disks INFO 320 week 9

  31. RAID 0+1 So if we do both mirroring and striping at once, we have RAID 0+1 RAID 0+1 is implemented as a mirrored array whose segments are RAID 0 (striped) arrays Hence we need at least four disks, and get the read speed boost of striping, and the redundancy of mirroring INFO 320 week 9

  32. RAID 3 RAID 3 does striping, plus adds a parity drive; 3 drive minimum The last drive has a parity bit from all of the other drives, used to reconstruct one drive if it fails Very high read and write speeds, high efficiency, good for multimedia data, but expensive and complex INFO 320 week 9

  33. RAID 5 RAID 5 is similar to RAID 3, but the parity information is distributed across all the drives; 3 drive minimum Hence if any one drive fails, it can be recreated from the other drives High read rate and efficiency, medium write rate Very commonly used for dB, web, file, and other servers INFO 320 week 9

  34. RAID 10 Notice that RAID 10 is not the same as RAID 0+1 RAID 10 is a striped array whose segments are RAID 1 arrays (mirrors) instead of single drives Minimum of 4 disks needed Good when you need higher performance than RAID 1; but very expensive INFO 320 week 9

  35. RAID 10 RAID 10 can handle multiple drive failures, as long as you don’t lose both halves of a mirrored pair INFO 320 week 9

  36. RAID 50 RAID 50 or 05 is striping two sets of RAID 5 arrays Minimum of six disks! Better redundancy, faster reads INFO 320 week 9

  37. RAID and Ubuntu A RAID 5 array can not be used as the boot partition in Ubuntu – GRUB can’t read it A boot partition can be RAID 1 RAID is configured during the partitioning process of installation Each partition is formatted to type ‘K raid’, and they are joined into an array as a multidisk (MD) device, then partitioned to /, /boot, swap INFO 320 week 9

  38. RAID and Ubuntu The main tools for administering RAID in Linux are /proc/mdstat and mdadm The former is a file with your current arrays cat /proc/mdstat Linux recognizes RAID 0, 1, 4, 5, 6 and 10 This is software-only RAID INFO 320 week 9

  39. RAID Capacity The usable capacity of common RAID levels is RAID 0 = # Drives x Cap Drive RAID 1 = (# Drives / 2) x Cap Drive RAID 3 or 5 = (# Drives -1) x Cap Drive RAID 3 and 5 ‘lose’ one drive’s capacity for parity information from the other drives, so larger arrays are more efficient From http://www.kintronics.com/raidwpaper.htm INFO 320 week 9

  40. Other RAIDs There are other RAID approaches (RAID 2, 4, 6, 7, 53, 1E, etc.) but combinations of RAID 0, 1, and 5 are most common Other storage technologies include JBOD DAS vs. NAS SAN INFO 320 week 9

  41. JBOD JBOD is Just a Bunch Of Disks RAID systems require identical drives JBOD allows combining physical drives into large logical volumes without requiring identical drives Cheap, easy, but no redundancy INFO 320 week 9

  42. DAS vs. NAS DAS is direct-attached storage, a fancy name for disks which are part of a server NAS (network-attached storage) is 100% dedicated to serving files over a network It’s one or more hard drives, with enough computer attached to let it communicate directly over the network Simple and cheap INFO 320 week 9

  43. SAN A Storage Area Network is a dedicated, high performance storage network Transfers data among servers and storage devices, separate from the local area network Used when high speed large transfers are common, often using fiber optic connections Often does load balancing and has high reliability Often used for transaction processing INFO 320 week 9

  44. SAN From http://www.rad-direct.com/Product-Whitepaper-IP-SAN-3.htm INFO 320 week 9

  45. Hot-swappable Finally, storage systems can have hot-swappable drives or not Hot-swappable means they can be safely removed from the system while it’s running Most RAID systems are hot-swappable, so that failed drives can be removed without reducing availability INFO 320 week 9

  46. References Bytepile, 2009. “RAID Types - Classifications ” from http://bytepile.com/raid_class.php The RAID Advisory Board (RAB) does not seem to exist any longer INFO 320 week 9

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