1.1 Apple OS X compared to Microsoft Windows

1.2 Apple OS X compared to Linux

But they are very different flavours of Unix!

1.3 Apple OS X compared to Linux - continued

Linux	OS X
/etc/init.d	Library/StartupItems /etc/mach_init.d since 10.3
/proc	different tools
iptables	ipfw
/etc/passwd	netinfo

• The options for many commands are different.

1.4 Unix software

Apple provides free downloads for Xcode (Developer Tools with compilers, debuggers, Java tools, Project Builder, Documentation etc.), X11, etc.

fink.sourceforge.net is an open source OS X software repository with binaries for many Unix tools (Gnome, KDE, Perl libraries, PDF and Postscript tools, databases, etc).

Installation of any other Unix software from source code is possible but can be difficult if the software does not explicitly support OS X.

2.1 OS X internals

• Aqua: user interface (including Desktop and Finder)

• Classic, Carbon, and Cocoa: application environments

• Quartz: windows + graphics (including OpenGL, QuickDraw, QuickTime, native PDF!)

• Darwin: operating system core (Mach 3.0, 4.4 BSD)

2.1.1 Remark: Microkernel vs. Monolithic System

Tanenbaum concluded in 1992 that "Linux is obsolete" ...

2.2 Application environments

• Classic emulator: legacy OS 9 code

• Carbon: procedural C-based APIs which run both on OS X and OS 9

• Cocoa: object-oriented API for developing in Objective-C and Java

• BSD commands

2.3 Processes

"ps -axw" shows both numbers.

If the Classic emulator is run, all its PSNs correspond to one PID.

2.4 Applications, Frameworks and Extensions

• Traditional applications are bundled into one directory (with .app extension).
  (In the GUI these look like a single executable.)

• Frameworks are collections of libraries (with .framework extension).

• Kernel Extensions (Plugins): dynamic loading of code into the kernel without recompilation.

2.5 AppleScript

tell application "Finder"
beep
    get the name of the first item in the desktop
end tell

3.1 OS X file system

• data fork: contains the actual user data

• resource fork: contains additional information, e.g. type and creator codes, thumbnail images, comments

3.2 Other features of HFS+

• HFS+ is a case preserving, case insensitive filesystem

• Each file and directory has a unique, persistent ID.

• Supports both creation and modification dates.

• Does not support sparse files, but zero-fills all bytes allocated for a file until end-of-file.

3.3 Aliases versus symbolic links

Aliases are references to an ID. They always refer to the same file even if it is moved. But they break if the file is replaced with a new version.

3.4 Working with the resource fork

Some BSD commands do not work with the resource fork!

3.5 Viewing the resource fork

• ls SOMEFILE/rsrc

3.6 BSD commands affected by the resource fork

• use "ditto" instead of "cp"

• use "hfstar" instead of "tar"

3.7 Other file systems (supported by OS X)

From a GUI view, there is no difference between these.

4.1 OS X System Startup

2) /System/Library/CoreServices/BootX (boot loader)

3) /sbin/mach_init (mach service naming)

4) /sbin/init (BSD init; PID 1; determines runlevel)

5) /etc/rc.boot (single user; netboot in case of network boot; fsck)

6) /etc/rc (multi-user startup; mount file system; cleanup; sysctl variables; syslogd; kextd; read mach_init.d; portmap; netinfo; update; vm; dynamic_pager )

7) /sbin/SystemStarter (/System/Library/StartupItems; /Library/StartupItems)

8) CoreGraphics; WindowServer; loginwindow

4.2 Startup items

Since OS 10.3: /etc/mach_init.d for system startup items and /etc/mach_init_per_user.d for user startup items. (Both are directories containing .plist files.)

5.1 Users and Groups

It is easiest to add users and groups using the GUI utilities.

• On the command-line, users can be added with niload passwd.
• On the command-line, the home directories can be created with

sudo ditto -rsrc /System/Library/User\ Template/English.lproj /Users/username

5.2 Remark: OS X Server

The server version has special GUI and command-line tools (such as serversetup and serveradmin) for all kinds of admin tasks.

5.3 Directory Services

• maintain information about all users (names, passwords, and preferences), printers and other resources on a network in a single location

• users can login to a computer on the network with their personal preferences

5.4 OS X's Open Directory

• LDAP or

• Netinfo (for local database)

• can be configured to act as client to Active Directory (Microsoft)

5.5 Open Directory Architecture (built into any Mac)

• Directory and authentication frameworks
  • Open Directory API
  • lookupd
  • PAM

• Directory services
  • BSD flatfiles (/etc)
  • Netinfo (local database + schema)
  • NIS (client)
  • LDAPv3 (client and custom map of OS X Server)
  • Active directory (client)
  • Crypt, kerberos, SASL (client)

5.6 Legacy Network Products that are supported

• AppleTalk: networking before OS X

• Rendezvous: zero configuration network for file sharing, printers, etc

• SLP: file and print services over IP

• SMB: Server Message Block (Microsoft)

5.7 lookupd: information broker and cache

• for user accounts, groups, printers, e-mail aliases, computer names, IP addresses

• keeps a cache of recently requested items to improve system performance.

• search strategy for DNS, for NIS, for flat files

• query directory services, Netinfo etc

• categories are users, groups, hosts, networks, services, protocols, rpcs, mounts, printers, bootparams, bootp, aliases, and netgroups.

6.1 Summary: OS X

OS X supports a variety of file system formats, networking protocols, directory access, etc.

OS X also supports pre-OS X legacy code which is not Unix-like at all.

Maybe: because Apple is not the market leader, OS X has to strive for compatibility with other systems.