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Understanding System Updates and User Management in Operating Systems

This lecture focuses on the vital aspects of system updates and user group management in operating systems. It covers the importance of regularly updating software, including kernel and third-party applications on Windows and Linux. Participants will learn about update mechanisms, package managers like apt-get and rpm/yum, and repository types, alongside user management principles involving user IDs (UIDs) and group IDs (GIDs). Key topics include community repositories, testing, and how to create and manage users and groups effectively.

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Understanding System Updates and User Management in Operating Systems

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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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