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Cosc 4750

Processes. Cosc 4750. Processes. All Processes have PID (Process ID) PPID (Parent Process ID) UID (User ID) and EUID (Effective UID) GID (Group ID) and EGID (Effective GID) Niceness It scheduling priority (range: -20 to +19) Control Terminal

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Cosc 4750

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  1. Processes Cosc 4750

  2. Processes • All Processes have • PID (Process ID) • PPID (Parent Process ID) • UID (User ID) and EUID (Effective UID) • GID (Group ID) and EGID (Effective GID) • Niceness • It scheduling priority (range: -20 to +19) • Control Terminal • The terminal it was launched from, where standard output goes

  3. Process “life cycle” • Each process is created by the Parent process coping itself with a fork system call • The new child process then uses the one of the exec commands start the run the program. • The child then runs to completion (or killed) and the parent always receives an exit code • 0 indicates normal or “successful” termination • The parent process must wait for the exit code or if the child process is “back grounded”, then acknowledge the child process finished.

  4. Ultimate parent process • The init process is the “Parent” of all processes. • Should a parent process terminate before a child process, init becomes the parent to the orphaned process • It will receive and acknowledge the child process exit code.

  5. Signaling a process • If a process is running the foreground • <control-c> will end the process • <control-z> suspends the process • In the background (or if root) • kill –9 <PID> or kill –KILL <PID> • Will terminate the process (almost always) • kill –1 <PID> or kill –HUP <PID> • will tell system processes to reread it’s config file otherwise, the process dies. • xkill (typed in shell), then click on a window • Will terminate the running window.

  6. Other signals: • -2 or –INT will interrupt, like <control-c>, if not caught, then process dies • -3 or –QUIT will “quit” the process with a core dump • -BUS causes a bus error and the process dies with a core dump • -SEGV causes a Segmentation fault, the process dies with a core dump • -WINCH causes an editor (like vi) to reconfigure itself.

  7. Kill –STOP <PID> suspends the process. • Kill –CONT <PID> will continue a suspended process • kill –TERM <PID> asks the process to terminate, but the process may ignore the request • There are other non-standard signals • man 7 signal • Will show you all the signals and their meaning.

  8. Process State • run: The process is executing or can run. • run/X: process is executing on processor X • Sleep: The process is waiting for a resource • Zombie/Defunct: process is trying to die • stop: the process is suspended

  9. Listing processes • ps –ef lists: • UID, PID, PPID, C, STIME, TTY, TIME, COMD • C=CPU use/scheduling info • STIME=Time the process was started • TTY=Control terminal • TIME=CPU time consumed • COMD= Command and arguments • ps –efaux • Lists the above and much more.

  10. TOP • lists process by CPU usage • adds to the nice, size, rss, state, %cpu, and %Mem • nice=is the priority the process is running at • state= the “state” the process is in • size=how big the program is • rss=how much memory it is using • %cpu=The percent of the cpu time it is using • %mem=The percent of memory it is using

  11. Nice & Renice • Sets the priority of a process • Normally a new process uses the priority of it’s parent process • Range between -20 and +19 • Highest priority is -20 • Lowest is +19 • nice +5 app • starts the app at +5 priority, normally priority 5

  12. Renice 19 <pid> • Sets the priority to 19 on that process • Renice 19 –u <user> • Sets the priority of all that users process to 19

  13. Periodic Processes • Using cron to schedule commands to be run • used to roll logs • backups • System filesystem clean up • any process you need to run every so often to complete a task.

  14. example: • 0 0 * * 5 /usr/local/bin/perl /backups/backup • Uses a set of time fields and then a command • minute hour day month weekday command • minute= 0-59 • hour= 0-23 • day=1-31 • month=1-12 • weekday=0-6 (Where 0=Sunday)

  15. 0 0 * * 5 /usr/local/bin/perl /backups/backup • * can be used in fields you don’t need/ not worried about • So the example, runs at Midnight, Friday night no matter, the day or month • 45 10 * * 1-5 find / -name core –exec rm –f {} \; • At 10:45am, Monday through Friday, removes any core file on the system.

  16. 45 10,22 * * 1-3,5 find / -name core –exec rm –f {} \; • At 10:45am and 10:45pm, Monday through Wednesday and friday, remove any core file on the system. 0,5,10,15,20,25,30,35,40,45,50,55 * * * /bin/getneworkinfo.pl • Every 5 minutes run the program /bin/getnetworkinfo.pl

  17. Crontab commands • crontab <filename> • Use <filename> as the cron file • crontab –l • lists cron file • crontab –r removes the cron file • crontab –e edit cron file with default editor

  18. Devices and Drivers

  19. Serial Devices • Serial Device files (Redhat) • /dev/cua[0,1,2,3] • (historical, for compatibly, but most systems no longer create them automatically.) • /dev/ttyS[0,1,2,3] • ttyS0 does not always mean Com port 1/A

  20. Set port settings • setserial –g /dev/ttyS0 • Displays the software settings for that serial port • setserial /dev/ttys1 port 0x02f8 irq 3 • changes the software settings • Does not change hardware settings, those must be changed in the bios.

  21. Terminals devices • A user enters a login name at a getty prompt • getty executes the login program • login requests a password and validates it with /etc/passwd • (at this point it very vendor specific and shell specific) • login prints the message of the day /etc/motd • login sets up the TERM environment variables and executes the shell • Shell then executes the appropriate startup files • Shell then waits for your input.

  22. Redhat and tcsh • getty gets the login name, then execs login for the password with the /etc/passwd • login display the motd • loginexecs tcsh (specified in the passwd file) • tcsh then sources /etc/csh.login, /etc/csh.cshrc, ~user/.cshrc, and ~user/.login • environment variables are setup in /etc/csh.login and /etc/csh.login. User specified variables from .cshrc and .login (note: .login is not always sourced)

  23. By default csh.cshrc only setups on the prompt • csh.login sets the following variables • PATH, umask, HOSTNAME, history, and other variables for programs like kerberos • Bash uses different files, /etc/profile, /etc/bashrc, ~user/.profile, ~user/.bash_profile, and ~user/.bash_login with similar results.

  24. login and tty • Every login is assigned to a tty. • There is no common naming convention for the login tty you use. • Redhat uses tty[0-12] and pts/X • SGI uses ttydX for console and ttyqX for most other logins • Sun uses pts/X and console (for console logins)

  25. Where do getty’s come from? • getty is exec’d by the init process, based on the configuration from the /etc/inittab file • Redhat default is 6 getty (called mingetty) • Each getty gets one tty[1-6] • When the last foreground process with tty1 (for example) exits/dies, then init creates a new mingetty process for tty1

  26. configuring your tty • stty allows you to configure your tty/ terminal. • stty intr ^C kill ^U erase ^H • setups up the terminal where <control-c> interrupts, <control-u> kills, and the “backspace” key is <control-h> • stty and stty –a • display the setting for your terminal. • tset automatically initializes your terminal to the settings for the TERM variable. • reset: resets you terminal back to “sane” settings • stty sane is the same as reset

  27. Other • parallel port(s) • parallel ports can be configured similarly • USB • “current” linux distro’s support USB. • The USB device is “mounted” into the filesystem. • Such camera’s, flash drives, etc… • For mice, and other devices without a filesystem, only a device file is created.

  28. inittab file • Determines how many console logins a linux system starts up • Normally, 6 console login prompts and the 7th is for the X-windows system • /etc/inittab works with the run-level • id:run-level:action:process so for the console • 1:2345:respawn:/sbin/mgetty tty1 • 2:2345:respawn:/sbin/mgetty tty2 • 3:2345:respawn:/sbin/mgetty tty3

  29. More actions • ctrlaltdel runs in response to <cntrl><alt><del> • Once start the process once • respawn start the process, then when it exits, spawn a new process • powerfail runs when the system gets a power fail signal

  30. Console logins • Some editors and cat’ing binary files can screw up your console (telnet, xterm, etc) • To fix these problems you can use one of two commands • sane Reset console settings to default • reset Reset console settings to default and clear buffers

  31. You can also use the command stty to set terminal settings • stty intr ^c erase ^? • Sets the <cntrl-c> to break current process • Sets the the backspace key to erase one character of input • stty –a • shows you all the settings for your term. • You can test varing things, if it does work, use the sane command to put back to default. • Note: Fedora logins do most of this for you.

  32. Adding disks • install the hardware • make sure properly connects and jumper’d (if needed) • make sure the hardware is recognized by the “bios” • UNIX will automatically create device files for recognized hardware • partition the drive as need (see dmesg for dev name) • fdisk or others example: fdisk /dev/hdb • Make the filesystem (like formating in windows) • mke2fs for ext2 fs or mke3fs for ext3 • mke3fs /dev/hdb1

  33. Standard filesystem • create an empty directory to mount it • mount the partition • add the mount to the fstab file for automatic mounting on boot up. • /dev/sdb1 /somedir ext3 defaults 0 0 • See the boot for a detailed step by step installation guide (software only)

  34. swap partitions • add swap partition to the swap space swapon /dev/hda2 (redhat example) • add partition the /etc/fstab file /dev/hda2 swap swap defaults 0 0

  35. check/repairing filesystems • fsck (linux and Sun) will check and attempt to repair filesystems • fsck –p /dev/hdaX is run by default on boot when the filesystem was not cleanly shutdown • fails on serious errors and asks for help • fsck /dev/hdaX will repair most errors, but needs user help.

  36. The Kernel • Linux kernel • 2.6.9-55.0.6 is the current kernel (Redhat anyway) • The first two numbers • even numbered kernels are production • odd numbered kernels are beta/test • The next major release of the kernel will be 2.8.0 (sometime in the future) • next minor release (might be) 2.6.10

  37. Building kernels • We used spend a great deal of time on building kernels for all major vendors with drivers. Chapter 27 will give you some information • With rpm, at least time is now spent on it. • Using rpmbuild we can rpm do must of the work. Look for the doc directory in /usr/src/redhat/BUILD/kernel-* for information on drivers and components. • lsmod displays loaded kernel modules • insmod loads manually a module into the kernel • at boot, configured in the /etc/conf.modules

  38. Q A &

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