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Lecture 11: Sys Admin-C

Lecture 11: Sys Admin-C. System Updates Operating System Programs User/Group Creation/Deletion UID/GID Limits wrt Permissions. System Updates. From time to time, operating systems need to be updated Kernel core updates Kernel module updates 3 rd party software also needs updated

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Lecture 11: Sys Admin-C

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  1. Lecture 11: Sys Admin-C • System Updates • Operating System • Programs • User/Group Creation/Deletion • UID/GID • Limits wrt Permissions

  2. System Updates • From time to time, operating systems need to be updated • Kernel core updates • Kernel module updates • 3rd party software also needs updated • What mechanisms do we use to perform these updates?

  3. Windows • Microsoft uses Windows update • What does it update? • Kernel core? • Kernel module updates? • 3rd party software?

  4. Windows • Microsoft uses Windows update • What does it update? • Kernel core? Yes • Kernel module updates? Yes • 3rd party software? Some • Microsoft products

  5. Windows • So how do non-Microsoft products get updated?

  6. Windows • So how do non-Microsoft products get updated? • They self-update • User manually checks • Software checks on launch • Software updated via daemon • Pros/cons of each?

  7. Linux • What mechanism does Linux use?

  8. Linux • What mechanism does Linux use? • Package manager • Debian-based  apt-get • RPM-based  rpm/yum • There are GUI front-ends to these tools

  9. Linux • What do these tools update?

  10. Linux • What do these tools update? • “Everything”! • New kernels • Module updates • 3rd party software • 3rd party software • gedit • firefox • libjpeg • kronos • libcurl • …

  11. Linux • There are things not included • Netbeans • … • For things that are included, where are updates coming from?

  12. Linux • There are things not included • Netbeans • … • For things that are included, where are updates coming from? • Repositories!

  13. Repositories • Each is a server that hosts software packages • Each hosts a “type” of update

  14. Repositories • core • It’s the stuff required to run an OS • Also includes some networking • Allows connecting to internet (repo access) • extra • Stuff that is useful, but not entirely required • X11 stuff (GUIs are necessary) • Development tools • etc

  15. Repositories • community • Community-based packages • Darwinism is controlling principle • They were essentially public packages in another repo • Became popular enough that a “Trusted User” brought it in here • multilib • Tools for building 32-bit libraries on 64-bit systems • “wine” is in here

  16. Repositories • testing • Packages that will go into ‘core’ or ‘extra’ repos • They are put here because they need the bugs worked out first • community-testing & multilib-testing • Packages for ‘community’ & ‘multilib’

  17. Repositories • These 7 are the “official” repositories for Arch Linux • Many servers “mirror” these repos • They copy the official repo and share • There are other repositories out there • You can enable them and then check stuff out • rpmforge, Nvidia, Dag RPM, etc

  18. Users/Groups • Let’s do Windows first because it’s quick and easy. • 2 types of users • Administrator • Does lots of nifty admin-y things • Limited User • Doesn’t do many nifty things • Usually just wrecks the system

  19. Users

  20. Groups

  21. Linux Users/Groups • Usernames aren’t usernames • It’s an alias to a user id (UID) • On another computer, your same username may have a different UID • When you do something on your system, you do it with a UID • Usually, this is your own UID

  22. Linux groups • They work the same way • Now it’s a group ID (GID) • We know we can join multiple groups • So how does this work?

  23. Linux groups • They work the same way • Now it’s a group ID (GID) • We know we can join multiple groups • So how does this work? • We have a primary GID, and then other GIDs.

  24. Username/Password Info • So where all this UID/GID stuff stored? • /etc/passwd • Let’s take a look at it!

  25. /etc/passwd • Username

  26. /etc/passwd • Password • ‘x’ means it’s encrypted in /etc/shadow

  27. /etc/passwd • User ID

  28. /etc/passwd • Group ID

  29. /etc/passwd • Miscellaneous info

  30. /etc/passwd • Home directory

  31. /etc/passwd • Default shell

  32. /etc/shadow • I won’t show you mine • It has my encrypted password • It’s encrypted. Why is the bearded man still squeamish about it?

  33. /etc/shadow • I won’t show you mine • It has my encrypted password • It’s encrypted. Why is the bearded man still squeamish about it? • There is no encryption that can’t be broken • Brute force • Educated guess (dictionary, birthdates, etc)

  34. /etc/group • Group name • Password • Group ID • Group list (members)

  35. Creating User/Group useradd -d /my/home/dir -g myGroup -s /bin/shuserName

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