Operating Systems 2019W Lecture 4: Difference between revisions

Latest revision as of 20:35, 17 January 2019

Video

Video from the lecture given on January 16, 2019 is now available.

Notes

Things discussed in lecture

conducting experiments to understand system behavior vs. reading documentation
Basic UNIX commands: cat, grep, wc, top
static and dynamic linking, system calls (hello.c from Tutorial 1)
/proc/self/exe
many system calls from strace of hello
C library (libc)
static linking includes more than necessary
dpkg -S to find package containing a file
ldd to see which dynamic libraries a file depends on
stand alone shell, sash (called ash in lecture)
BusyBox
- statically linked
- little version of common parts of UNIX userland
- BusyBox plus Linux kernel = almost complete small Linux system
disassembly of hello using objdump -d
- functions invoked using call, system calls invoked using syscall
X Window system versus Wayland
- X Window system: standard way of displaying graphical applications on UNIX-like systems
- Wayland: modern replacement of X used with lots of backwards compatibility
investigation of what happens when a window is closed (socket connection is terminated, but thought signal was sent)
signals
- short messages sent to processes
- can be sent by the kill system call (and kill command)
- kill <process ID> sends TERM signal by default
- KILL causes process to die without cleanup (TERM allows for handler to do cleanup)
- have default handlers, most can be changed except for STOP and KILL
- Could catch bad memory access by catching SEGV signal
- can stop and restart processes using signals (STOP and CONT), CONT doesn't always work though

@@ Line 5: / Line 5: @@
 ==Notes==
-Topics
+Things discussed in lecture
-*
+* conducting experiments to understand system behavior vs. reading documentation
+* Basic UNIX commands: cat, grep, wc, top
+* static and dynamic linking, system calls (hello.c from Tutorial 1)
+* /proc/self/exe
+* many system calls from strace of hello
+* C library (libc)
+* static linking includes more than necessary
+* dpkg -S to find package containing a file
+* ldd to see which dynamic libraries a file depends on
+* stand alone shell, [https://en.wikipedia.org/wiki/Stand-alone_shell sash] (called ash in lecture)
+* [https://en.wikipedia.org/wiki/BusyBox BusyBox]
+** statically linked
+** little version of common parts of UNIX userland
+** BusyBox plus Linux kernel = almost complete small Linux system
+* disassembly of hello using objdump -d
+** functions invoked using call, system calls invoked using syscall
+* [https://en.wikipedia.org/wiki/X_Window_System X Window system] versus [https://en.wikipedia.org/wiki/Wayland_(display_server_protocol) Wayland]
+** X Window system: standard way of displaying graphical applications on UNIX-like systems
+** Wayland: modern replacement of X used with lots of backwards compatibility
+* investigation of what happens when a window is closed (socket connection is terminated, but thought signal was sent)
+* signals
+** short messages sent to processes
+** can be sent by the kill system call (and kill command)
+** kill <process ID> sends TERM signal by default
+** KILL causes process to die without cleanup (TERM allows for handler to do cleanup)
+** have default handlers, most can be changed except for STOP and KILL
+** Could catch bad memory access by catching SEGV signal
+** can stop and restart processes using signals (STOP and CONT), CONT doesn't always work though