Cosc 4750

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Cosc 4750

• Processes

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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

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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.

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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.

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Signaling a process

• If a process is running the foreground
• ltcontrol-cgt will end the process
• ltcontrol-zgt suspends the process
• In the background (or if root)
• kill 9 ltPIDgt or kill KILL ltPIDgt
• Will terminate the process (almost always)
• kill 1 ltPIDgt or kill HUP ltPIDgt
• will tell system processes to reread its config
  file otherwise, the process dies.
• xkill (typed in shell), then click on a window
• Will terminate the running window.

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• Other signals
• -2 or INT will interrupt, like ltcontrol-cgt, 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.

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• Kill STOP ltPIDgt suspends the process.
• Kill CONT ltPIDgt will continue a suspended
  process
• kill TERM ltPIDgt 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.

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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

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Listing processes

• ps ef lists
• UID, PID, PPID, C, STIME, TTY, TIME, COMD
• CCPU use/scheduling info
• STIMETime the process was started
• TTYControl terminal
• TIMECPU time consumed
• COMD Command and arguments
• ps efaux
• Lists the above and much more.

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TOP

• lists process by CPU usage
• adds to the nice, size, rss, state, cpu, and
  Mem
• niceis the priority the process is running at
• state the state the process is in
• sizehow big the program is
• rsshow much memory it is using
• cpuThe percent of the cpu time it is using
• memThe percent of memory it is using

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Nice Renice

• Sets the priority of a process
• Normally a new process uses the priority of its
  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

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• Renice 19 ltpidgt
• Sets the priority to 19 on that process
• Renice 19 u ltusergt
• Sets the priority of all that users process to 19

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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.

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• 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
• day1-31
• month1-12
• weekday0-6 (Where 0Sunday)

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• 0 0 5 /usr/local/bin/perl /backups/backup
• can be used in fields you dont 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 1045am, Monday through Friday, removes any
  core file on the system.

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• 45 10,22 1-3,5 find / -name core exec rm f
  \
• At 1045am and 1045pm, 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

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Crontab commands

• crontab ltfilenamegt
• Use ltfilenamegt as the cron file
• crontab l
• lists cron file
• crontab r removes the cron file
• crontab e edit cron file with default editor

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• Devices and Drivers

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Serial Devices

• Serial Device files (Redhat)
• /dev/cua0,1,2,3
• (historical, for compatibly, but most systems
  no longer create them automatically.)
• /dev/ttyS0,1,2,3
• ttyS0 does not always mean Com port 1/A

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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.

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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.

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Redhat and tcsh

• getty gets the login name, then execs login for
  the password with the /etc/passwd
• login display the motd
• login execs 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)

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• 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.

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login and tty

• Every login is assigned to a tty.
• There is no common naming convention for the
  login tty you use.
• Redhat uses tty0-12 and pts/X
• SGI uses ttydX for console and ttyqX for most
  other logins
• Sun uses pts/X and console (for console logins)

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Where do gettys come from?

• getty is execd by the init process, based on the
  configuration from the /etc/inittab file
• Redhat default is 6 getty (called mingetty)
• Each getty gets one tty1-6
• When the last foreground process with tty1 (for
  example) exits/dies, then init creates a new
  mingetty process for tty1

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configuring your tty

• stty allows you to configure your tty/ terminal.
  
• stty intr C kill U erase H
• setups up the terminal where ltcontrol-cgt
  interrupts, ltcontrol-ugt kills, and the
  backspace key is ltcontrol-hgt
• 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

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Other

• parallel port(s)
• parallel ports can be configured similarly
• USB
• current linux distros support USB.
• The USB device is mounted into the filesystem.
• Such cameras, flash drives, etc
• For mice, and other devices without a filesystem,
  only a device file is created.

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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
• idrun-levelactionprocess so for the console
• 12345respawn/sbin/mgetty tty1
• 22345respawn/sbin/mgetty tty2
• 32345respawn/sbin/mgetty tty3

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• More actions
• ctrlaltdel runs in response to ltcntrlgtltaltgtltdelgt
• 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

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Console logins

• Some editors and cating 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

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• You can also use the command stty to set terminal
  settings
• stty intr c erase ?
• Sets the ltcntrl-cgt 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.

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Adding disks

• install the hardware
• make sure properly connects and jumperd (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

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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)

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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

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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.

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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

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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/BUIL
  D/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

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Q
A