List of Slides

1

– General Linux 1 – Create, Monitor, and Kill Processes [7]
(Linux Professional Institute Certification)
a .˜. /V\ // \\ @._.@

by: geoffrey robertson geoffrey@zip.com.au

$Id: gl1.103.5.slides.tex,v 1.2 2003/05/30 05:06:17 waratah Exp $

c 2002 Geoffrey Robertson. Permission is granted to make and distribute verbatim copies or modified versions of this document provided that this copyright notice and this permission notice are preserved on all copies under the terms of the GNU General Public License as published by the Free Software Foundation— either version 2 of the License or (at your option) any later version.

a Copyright

2

Overview
GNU & Unix Commands
1.103.1 Work on the command line 1.103.2 Process text streams using filters 1.103.3 Perform basic file management 1.103.4 Use streams, pipes, and redirects 1.103.5 Create, monitor, and kill processes 1.103.6 Modify process execution priorities 1.103.7 Search text files using regular expressions

3

Create, Monitor, and Kill Processes
Objective
Candidate should be able to manage processes. This includes knowing how to run jobs in the foreground and background, bring a job from the background to the foreground and vice versa, start a process that will run without being connected to a terminal and signal a program to continue running after logout. Tasks also include monitoring active processes, selecting and sorting processes for display, sending signals to processes, killing processes and identifying and killing X applications that did not terminate after the X session closed.

4

Create, Monitor, and Kill Processes
Key files, terms, and utilities
& bg fg jobs kill nohup ps top

5

Create, Monitor, and Kill Processes
Resources of interest

6

Processes
• A process is an executable loaded in memory. • Linux is a multitasking operating system and so runs many processes concurrently.

7

Processes
• A process is an executable loaded in memory. • Linux is a multitasking operating system and so runs many processes concurrently. • INIT (PID 1) is the mother of all processes.

7-a

Processes
• A process is an executable loaded in memory. • Linux is a multitasking operating system and so runs many processes concurrently. • INIT (PID 1) is the mother of all processes. • Programs, daemons, shells and commands are all processes.

7-b

Processes
• A process is an executable loaded in memory. • Linux is a multitasking operating system and so runs many processes concurrently. • INIT (PID 1) is the mother of all processes. • Programs, daemons, shells and commands are all processes. • The kernel automatically manages processes.

7-c

Processes
• A process is an executable loaded in memory. • Linux is a multitasking operating system and so runs many processes concurrently. • INIT (PID 1) is the mother of all processes. • Programs, daemons, shells and commands are all processes. • The kernel automatically manages processes. • Normally processes live, execute and die without intervention from users.

7-d

Process Attributes and Concepts
The kernel starts the first process: init which has PID 1

8

Process Attributes and Concepts
The kernel starts the first process: init which has PID 1 Lifetime: Each process starts when it’s command is executed, and lives till it dies or is killed.

8-a

Process Attributes and Concepts
The kernel starts the first process: init which has PID 1 Lifetime: Each process starts when it’s command is executed, and lives till it dies or is killed. Process ID (PID): Every process has a unique number assigned to it when it is started.

8-b

Process Attributes and Concepts
The kernel starts the first process: init which has PID 1 Lifetime: Each process starts when it’s command is executed, and lives till it dies or is killed. Process ID (PID): Every process has a unique number assigned to it when it is started. User ID and Group ID: Processes have the privileges associated with the user / group who started them.

8-c

Process Attributes and Concepts
The kernel starts the first process: init which has PID 1 Lifetime: Each process starts when it’s command is executed, and lives till it dies or is killed. Process ID (PID): Every process has a unique number assigned to it when it is started. User ID and Group ID: Processes have the privileges associated with the user / group who started them. Parent processes (PPID): Shell processes are descendants of init and commands run from them are child processes.

8-d

Process Attributes and Concepts
The kernel starts the first process: init which has PID 1 Lifetime: Each process starts when it’s command is executed, and lives till it dies or is killed. Process ID (PID): Every process has a unique number assigned to it when it is started. User ID and Group ID: Processes have the privileges associated with the user / group who started them. Parent processes (PPID): Shell processes are descendants of init and commands run from them are child processes. Environment: Each process inherits a set of environmental variables from it’s parent process.

8-e

Process Attributes and Concepts
The kernel starts the first process: init which has PID 1 Lifetime: Each process starts when it’s command is executed, and lives till it dies or is killed. Process ID (PID): Every process has a unique number assigned to it when it is started. User ID and Group ID: Processes have the privileges associated with the user / group who started them. Parent processes (PPID): Shell processes are descendants of init and commands run from them are child processes. Environment: Each process inherits a set of environmental variables from it’s parent process. Current Working Directory: Each process starts with a default directory.

8-f

Process Monitoring
Processes have to be monitored so as to check their health and use of system resources.

9

Process Monitoring
Processes have to be monitored so as to check their health and use of system resources. • ps
$ ps aux |grep ssh root 866 0.0 0.3 2676 1268 ? S 07:56 0:00 /usr/sbin/sshd

9-a

Process Monitoring
Processes have to be monitored so as to check their health and use of system resources. • ps
$ ps aux |grep ssh root 866 0.0 0.3 2676 1268 ? S 07:56 0:00 /usr/sbin/sshd

• pstree
$ pstree init-+-alarmd |-apmd |-kdeinit-+-autorun | |-kdeinit---emacs

9-b

Process Monitoring
Processes have to be monitored so as to check their health and use of system resources. • ps
$ ps aux |grep ssh root 866 0.0 0.3 2676 1268 ? S 07:56 0:00 /usr/sbin/sshd

• pstree
$ pstree init-+-alarmd |-apmd |-kdeinit-+-autorun | |-kdeinit---emacs

• top
$ top PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM 1792 geoffrey 11 0 8796 8796 7932 S 0.3 2.2 1590 root 14 0 57512 13M 2572 R 0.1 3.6 2857 geoffrey 14 0 1056 1056 836 R 0.1 0.2 TIME 0:01 0:41 0:01 COMMAND kdeinit X top

9-c

Process Management
Normally the kernel automatically manages processes. However sometimes processes have to be started, stopped, restarted and killed.

10

Process Management
Normally the kernel automatically manages processes. However sometimes processes have to be started, stopped, restarted and killed. • Starting a process:
# /usr/sbin/httpd ps aux |grep httpd root 2987 0.0 apache 3003 0.0

0.4 0.4

4512 1584 ? 4656 1672 ?

/usr/sbin/httpd /usr/sbin/httpd

10-a

Process Management
Normally the kernel automatically manages processes. However sometimes processes have to be started, stopped, restarted and killed. • Starting a process:
# /usr/sbin/httpd ps aux |grep httpd root 2987 0.0 apache 3003 0.0

0.4 0.4

4512 1584 ? 4656 1672 ?

/usr/sbin/httpd /usr/sbin/httpd

• Occasionally processes die and have to be restarted.

10-b

Process Management
Normally the kernel automatically manages processes. However sometimes processes have to be started, stopped, restarted and killed. • Starting a process:
# /usr/sbin/httpd ps aux |grep httpd root 2987 0.0 apache 3003 0.0

0.4 0.4

4512 1584 ? 4656 1672 ?

/usr/sbin/httpd /usr/sbin/httpd

• Occasionally processes die and have to be restarted. • Processes may go berserk and have to be killed.
# kill -9 1234

10-c

Process Management
Normally the kernel automatically manages processes. However sometimes processes have to be started, stopped, restarted and killed. • Starting a process:
# /usr/sbin/httpd ps aux |grep httpd root 2987 0.0 apache 3003 0.0

0.4 0.4

4512 1584 ? 4656 1672 ?

/usr/sbin/httpd /usr/sbin/httpd

• Occasionally processes die and have to be restarted. • Processes may go berserk and have to be killed.
# kill -9 1234

• After configuration changes processes may have to be restarted so as to re-read their configuration files.
# service xinetd restart Stopping xinetd: Starting xinetd: [ [ OK OK ] ]

10-d

What is multitasking?
Multitasking is used to describe the situation where one processor (CPU) is used to perform multiple tasks concurrently.

11

What is multitasking?
Multitasking is used to describe the situation where one processor (CPU) is used to perform multiple tasks concurrently. • Only one task or program is executing instructions on the CPU.

11-a

What is multitasking?
Multitasking is used to describe the situation where one processor (CPU) is used to perform multiple tasks concurrently. • Only one task or program is executing instructions on the CPU. • The CPU must be regularly switched between each program and others.

11-b

What is multitasking?
Multitasking is used to describe the situation where one processor (CPU) is used to perform multiple tasks concurrently. • Only one task or program is executing instructions on the CPU. • The CPU must be regularly switched between each program and others. • This process is known as a task switch.

11-c

What is multitasking?
Multitasking is used to describe the situation where one processor (CPU) is used to perform multiple tasks concurrently. • Only one task or program is executing instructions on the CPU. • The CPU must be regularly switched between each program and others. • This process is known as a task switch. • At each task switch the Linux kernel must save the context of the CPU.

11-d

What is multitasking?
Multitasking is used to describe the situation where one processor (CPU) is used to perform multiple tasks concurrently. • Only one task or program is executing instructions on the CPU. • The CPU must be regularly switched between each program and others. • This process is known as a task switch. • At each task switch the Linux kernel must save the context of the CPU. • The operating system uses the saved context when it switches back to the task the next time it gets some CPU time scheduled to it.

11-e

Task Scheduling
The total number of slices, when, how often and for how long the CPU is switched is determined by the multitasking algorithm and is handled by a software component within the kernel know as the task scheduler.

12

Task Scheduling
The total number of slices, when, how often and for how long the CPU is switched is determined by the multitasking algorithm and is handled by a software component within the kernel know as the task scheduler. There are three basic types of task scheduling:

12-a

Task Scheduling
The total number of slices, when, how often and for how long the CPU is switched is determined by the multitasking algorithm and is handled by a software component within the kernel know as the task scheduler. There are three basic types of task scheduling: Nonpreemptive: A task must relinquish the CPU before a task switch occurs.

12-b

Task Scheduling
The total number of slices, when, how often and for how long the CPU is switched is determined by the multitasking algorithm and is handled by a software component within the kernel know as the task scheduler. There are three basic types of task scheduling: Nonpreemptive: A task must relinquish the CPU before a task switch occurs. Preemptive: The kernel takes away the CPU from a task without notice.

12-c

Task Scheduling
The total number of slices, when, how often and for how long the CPU is switched is determined by the multitasking algorithm and is handled by a software component within the kernel know as the task scheduler. There are three basic types of task scheduling: Nonpreemptive: A task must relinquish the CPU before a task switch occurs. Preemptive: The kernel takes away the CPU from a task without notice. Realtime: Tasks are prioritised. High priority tasks must complete before a task switch.

12-d

What is a Process?
The term process is a fundamental abstraction.

13

What is a Process?
The term process is a fundamental abstraction. • Two of the more traditional definitions of a process are: “A program in execution.” “A single program running in its own virtual address space”

13-a

What is a Process?
The term process is a fundamental abstraction. • Two of the more traditional definitions of a process are: “A program in execution.” “A single program running in its own virtual address space” • In practice, a process is simply an executable that has been loaded into memory and is either running or ready to run on the system.

13-b

Process types
Processes under Linux fall into three basic categories:

14

Process types
Processes under Linux fall into three basic categories: Interactive Process: An interactive process is a process initiated from (and controlled by) a shell. Interactive processes may be in foreground or background. (Example: ls, ls &)

14-a

Process types
Processes under Linux fall into three basic categories: Interactive Process: An interactive process is a process initiated from (and controlled by) a shell. Interactive processes may be in foreground or background. (Example: ls, ls &) Batch Process: A batch process is a process that is not associated with a terminal but is submitted to a queue to be executed sequentially. (Example slocate started by cron)

14-b

Process types
Processes under Linux fall into three basic categories: Interactive Process: An interactive process is a process initiated from (and controlled by) a shell. Interactive processes may be in foreground or background. (Example: ls, ls &) Batch Process: A batch process is a process that is not associated with a terminal but is submitted to a queue to be executed sequentially. (Example slocate started by cron) Daemon Process: A daemon process is a process that runs in the background until it’s required. This kind of processes is usually initiated when Linux boots. (Example: inetd, lpd)

14-c

Elements associated with a process
For each process running on the system, the kernel needs to keep a list of resources used by that process. Some of these resources include:

15

Elements associated with a process
For each process running on the system, the kernel needs to keep a list of resources used by that process. Some of these resources include: • tty association (tty struct)

15-a

Elements associated with a process
For each process running on the system, the kernel needs to keep a list of resources used by that process. Some of these resources include: • tty association (tty struct) • file system (eg current directory & open files) (fs struct, files struct)

15-b

Elements associated with a process
For each process running on the system, the kernel needs to keep a list of resources used by that process. Some of these resources include: • tty association (tty struct) • file system (eg current directory & open files) (fs struct, files struct) • memory allocation (mm struct)

15-c

Elements associated with a process
For each process running on the system, the kernel needs to keep a list of resources used by that process. Some of these resources include: • tty association (tty struct) • file system (eg current directory & open files) (fs struct, files struct) • memory allocation (mm struct) • Signals received (signal struct)

15-d

Process States
At any given point in time, a process is in one of 5 states:

16

Process States
At any given point in time, a process is in one of 5 states: TASK RUNNING: The process is either executing on the CPU or waiting to be executed.

16-a

Process States
At any given point in time, a process is in one of 5 states: TASK RUNNING: The process is either executing on the CPU or waiting to be executed. TASK INTERRUPTIBLE: The process is sleeping until something becomes true. Raising a hardware interrupt, waiting for a system resource etc are examples of a condition that might wake the process up. If a signal is received by the process (eg KILL -HUP) the process will also be woken up.

16-b

Process States
At any given point in time, a process is in one of 5 states: TASK RUNNING: The process is either executing on the CPU or waiting to be executed. TASK INTERRUPTIBLE: The process is sleeping until something becomes true. Raising a hardware interrupt, waiting for a system resource etc are examples of a condition that might wake the process up. If a signal is received by the process (eg KILL -HUP) the process will also be woken up. TASK UNINTERRUPTIBLE: Like the previous state except that delivering a signal will not wake the process up.

16-c

Process States
At any given point in time, a process is in one of 5 states: TASK RUNNING: The process is either executing on the CPU or waiting to be executed. TASK INTERRUPTIBLE: The process is sleeping until something becomes true. Raising a hardware interrupt, waiting for a system resource etc are examples of a condition that might wake the process up. If a signal is received by the process (eg KILL -HUP) the process will also be woken up. TASK UNINTERRUPTIBLE: Like the previous state except that delivering a signal will not wake the process up. TASK STOPPED: Process execution has stopped. A process enters this state after receiving a SIGSTOP signal. A debugger may use this to step through a program.

16-d

Process States
At any given point in time, a process is in one of 5 states: TASK RUNNING: The process is either executing on the CPU or waiting to be executed. TASK INTERRUPTIBLE: The process is sleeping until something becomes true. Raising a hardware interrupt, waiting for a system resource etc are examples of a condition that might wake the process up. If a signal is received by the process (eg KILL -HUP) the process will also be woken up. TASK UNINTERRUPTIBLE: Like the previous state except that delivering a signal will not wake the process up. TASK STOPPED: Process execution has stopped. A process enters this state after receiving a SIGSTOP signal. A debugger may use this to step through a program. TASK ZOMBIE: Process execution has stopped but the kernel has not yet ?cleaned up? the resources allocated to the process.

16-e

The Process Family Tree
Every process (with the sole exception of the kernel), must be created by another process. The terms parent, child and sibling (or sometimes father, son and brother in a patriarchal sense) are used to describe the relationships between processes. As an example consider the following line executed from the bash prompt: [andy@Node4] andy]$ ls & df -h & The following relationships are true:

17

The Process Family Tree
Every process (with the sole exception of the kernel), must be created by another process. The terms parent, child and sibling (or sometimes father, son and brother in a patriarchal sense) are used to describe the relationships between processes. As an example consider the following line executed from the bash prompt: [andy@Node4] andy]$ ls & df -h & The following relationships are true: • The ls and df processes are both siblings to each other.

17-a

The Process Family Tree
Every process (with the sole exception of the kernel), must be created by another process. The terms parent, child and sibling (or sometimes father, son and brother in a patriarchal sense) are used to describe the relationships between processes. As an example consider the following line executed from the bash prompt: [andy@Node4] andy]$ ls & df -h & The following relationships are true: • The ls and df processes are both siblings to each other. • The bash process (ie the shell) is the parent to both ls and df.

17-b

The Process Family Tree
Every process (with the sole exception of the kernel), must be created by another process. The terms parent, child and sibling (or sometimes father, son and brother in a patriarchal sense) are used to describe the relationships between processes. As an example consider the following line executed from the bash prompt: [andy@Node4] andy]$ ls & df -h & The following relationships are true: • The ls and df processes are both siblings to each other. • The bash process (ie the shell) is the parent to both ls and df. • The ls process has bash as its parent.

17-c

The Process Family Tree
Every process (with the sole exception of the kernel), must be created by another process. The terms parent, child and sibling (or sometimes father, son and brother in a patriarchal sense) are used to describe the relationships between processes. As an example consider the following line executed from the bash prompt: [andy@Node4] andy]$ ls & df -h & The following relationships are true: • The ls and df processes are both siblings to each other. • The bash process (ie the shell) is the parent to both ls and df. • The ls process has bash as its parent. • The df process has bash as its parent.

17-d

The Kernel is at the Top of the Family Tree

Kernel --> Init --> all other processes --> even more processes -->

18

The Kernel is at the Top of the Family Tree
• When Linux boots, the first thing it does is load the kernel into memory and start executing itself.

Kernel --> Init --> all other processes --> even more processes -->

18-a

The Kernel is at the Top of the Family Tree
• When Linux boots, the first thing it does is load the kernel into memory and start executing itself. • One of the first things it does once execution starts, is to spawn a process called init, which in turn spawns other processes.

Kernel --> Init --> all other processes --> even more processes -->

18-b

The Kernel is at the Top of the Family Tree
• When Linux boots, the first thing it does is load the kernel into memory and start executing itself. • One of the first things it does once execution starts, is to spawn a process called init, which in turn spawns other processes. • In this sense, the kernel is at the top of the family tree, with only one child process called init.

Kernel --> Init --> all other processes --> even more processes -->

18-c

The Kernel is at the Top of the Family Tree
• When Linux boots, the first thing it does is load the kernel into memory and start executing itself. • One of the first things it does once execution starts, is to spawn a process called init, which in turn spawns other processes. • In this sense, the kernel is at the top of the family tree, with only one child process called init. • Init in turn has many children and probably many grandchildren. Kernel --> Init --> all other processes --> even more processes -->

18-d

Process IDs
In order for the kernel to keep track of all processes and their descendants, a process ID is assigned to every process running on the system. Process IDs are just numbers and run from 0 to 32767. The number 32767 is the largest signed integer available with a sixteen bit word size and is used to maintain backward compatibility with 16 bit architectures. There are two PIDs (process IDs) that are always the same: • kernel PID is always 0 • init PID is always 1

19

Process IDs
Each time a new process is created, a new PID is allocated and is equal to the last PID issued plus one. Once the last PID is reached, the PID wraps back around to zero and the next available PID is used (note that 0 and 1 will never be available). This scheme is a little like the assignment of telephone numbers: When a telephone service is disconnected, rather than just assigning the old telephone number to a new subscriber, the old number remains out of use until all other numbers have been used up. This saves “wrong numbers” to the new subscriber from callers who have not yet realised that the old number is no longer connected to the person they were trying to reach. In a similar vein, the kernel does this to minimise “wrong numbers” from other processes who have not yet worked out that their intended process no longer exists. This is especially true for Interprocess Communication (IPC) which uses the PID to identify a target process.

20

Displaying Process Information
There are three utilities used to display the state of running processes: • ps • pstree • top

21

Displaying Process Information
There are three utilities used to display the state of running processes: • ps • pstree • top • The ps command is used to display a “snapshot” of all processes running on the system at the time the ps command was executed.

21-a

Displaying Process Information
There are three utilities used to display the state of running processes: • ps • pstree • top • The ps command is used to display a “snapshot” of all processes running on the system at the time the ps command was executed. • pstree gives a tree view of the processes.

21-b

Displaying Process Information
There are three utilities used to display the state of running processes: • ps • pstree • top • The ps command is used to display a “snapshot” of all processes running on the system at the time the ps command was executed. • pstree gives a tree view of the processes. • The top command is used to display a real-time display of all processes running on the system. Top can also be used in interactive mode to kill or renice (change priority) of a process.

21-c

Process Monitoring—ps
usage: ps [options] The ps command has a huge number of switches. The switches can be subdivided into two main groups: • Process selection (which processes to display) • Output control (how and what output should be displayed)

22

ps options
$ ps ? ERROR: Garbage option. ********* simple selection ********* ********* selection by list ********* -A all processes -C by command name -N negate selection -G by real group ID (supports names) -a all w/ tty except session leaders -U by real user ID (supports names) -d all except session leaders -g by session leader OR by group name -p by process ID -e all processes T all processes on this terminal -s processes in the sessions given a all w/ tty, including other users -t by tty g all, even group leaders! -u by effective user ID (supports names) r only running processes U processes for specified users t by tty x processes w/o controlling ttys *********** output format ********** *********** long options *********** --Group --User --pid --cols -o,o user-defined -f full -j,j job control s signal --group --user --sid --rows -O,O preloaded -o v virtual memory --cumulative --format --deselect -l,l long u user-oriented --sort --tty --forest --version X registers --heading --no-heading ********* misc options ********* -V,V show version L list format codes f ASCII art forest -m,m show threads S children in sum -y change -l format -n,N set namelist file c true command name n numeric WCHAN,UID -w,w wide output e show environment -H process heirarchy

23

ps options
The switches that need to be known for the purposes of LPIC are as follows: a Display processes for all users txx Display processes within controlling terminal txx u Display user information for the process l Display in long format with detailed information s Display signal information m Display memory information x Display processes without a controlling terminal S Display CPU time and page faults of child processes -C cmd Search for instances of command cmd. -f Forest mode shows process family trees. -w Wide format

24

ps field names & their meanings
USER The user who started the process PID The process ID %CPU Shows the cputime / realtime percentage. %MEM The fraction of RSS divided by the total size of RAM VSZ Size of virtual memory used by the process RSS Resident set size (Data & Text segments only) in Kb TTY The TTY associated with this process STAT The current status (DRSTZW< NL) (details next slide) TIME CPU time in MINS:SECS COMMAND The full command line used to start the process

25

ps Status Field
$ ps aux USER PID %CPU %MEM root 1 0.0 0.0 VSZ 1304 RSS TTY 72 ? STAT START S Mar21 TIME COMMAND 0:19 init

D uninterruptible sleep (usually IO) R runnable (on run queue) S sleeping T traced or stopped Z a defunct (“zombie”) process W has no resident pages < high-priority process N low-priority task L has pages locked into memory (for real-time and custom IO)

26

ps Status Field
$ ps aux USER root root root root root root root root root root root rpc rpcuser ntp root root ..... andy root andy PID %CPU %MEM 1 0.0 0.2 2 0.0 0.0 3 0.0 0.0 5 0.0 0.0 6 0.0 0.0 7 0.0 0.0 8 0.0 0.0 9 0.0 0.0 103 0.0 0.0 474 0.0 0.2 479 0.0 0.4 497 0.0 0.2 525 0.0 0.3 735 0.0 0.8 759 0.0 0.3 763 0.0 0.3 1176 1343 1664 0.0 0.0 0.0 0.5 0.7 0.3 VSZ RSS TTY 1384 516 ? 0 0? 0 0? 0 0? 0 0? 0 0? 0 0? 0 0? 0 0? 1444 620 ? 2080 1152 ? 1632 708 ? 1624 796 ? 2088 2080 ? 5784 856 ? 5784 856 ? 2620 1508 pts/0 3000 1816 tty1 2824 924 pts/1 STAT S SW SW SW SW SW SW SW< SW S S S S SL S S S S R START 11:43 11:43 11:43 11:43 11:43 11:43 11:43 11:43 11:44 11:44 11:44 11:44 11:44 11:44 11:44 11:44 11:46 15:21 21:52 TIME 0:04 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 COMMAND init [5] [keventd] [kapm-idled] [kswapd] [kreclaimd] [bdflush] [kupdated] [mdrecoveryd] [kjournald] syslogd -m 0 klogd -2 portmap rpc.statd ntpd -U ntp ypbind ypbind

0:00 bash 0:00 ssh node10 0:00 ps -aux

27

Process Monitoring—pstree
$ pstree init-+-anacron---run-parts---cfengine |-5*[apache-ssl] |-atd |-bash---startx---xinit-+-X | ‘-enlightenment-+-E-Clock.epplet | |-E-Cpu.epplet | |-Emix.epplet | |-Eterm---bash-+-abiword---AbiWord | | ‘-mozilla-bin---moz | |-Eterm---bash---bash | |-Eterm---bash | |-Eterm---bash---gv---gs | |-Eterm---bash---mutt | |-Eterm---bash---emacs-+-ispell | | ‘-xdvi---gs | |-Eterm---bash---pstree | ‘-Eterm---bash---man---pager |-cron |-gcache |-6*[getty] |-inetd---nmbd |-junkbuster

28

pstree options
Three commonly used options for pstree:

29

pstree options
Three commonly used options for pstree: -a Show command line arguments. |-xfs -daemon |-xfstt --port 7101 --daemon --user nobody ‘-zope-z2 /usr/sbin/zope-z2 ‘-python /usr/sbin/zope-z2

29-a

pstree options
Three commonly used options for pstree: -a Show command line arguments. |-xfs -daemon |-xfstt --port 7101 --daemon --user nobody ‘-zope-z2 /usr/sbin/zope-z2 ‘-python /usr/sbin/zope-z2 -n Sort processes with the same ancestor by PID

29-b

pstree options
Three commonly used options for pstree: -a Show command line arguments. |-xfs -daemon |-xfstt --port 7101 --daemon --user nobody ‘-zope-z2 /usr/sbin/zope-z2 ‘-python /usr/sbin/zope-z2 -n Sort processes with the same ancestor by PID -p Show PIDs. init(1)-+-anacron(27095)---run-parts(27755)---cfengine(27765) |-apache-ssl(27188) |-apache-ssl(27189)

29-c

Process Monitoring—top
The ”top” command provides a continuously updated, real-time look at process activity, memory and swap file usage plus CPU activity. It also shows what processes are running and by whom.

30

Process Monitoring—top
The ”top” command provides a continuously updated, real-time look at process activity, memory and swap file usage plus CPU activity. It also shows what processes are running and by whom. • Its primary use is as an administration and system information tool. It provides an extension to the functionality of the ”ps” command.

30-a

Process Monitoring—top
The ”top” command provides a continuously updated, real-time look at process activity, memory and swap file usage plus CPU activity. It also shows what processes are running and by whom. • Its primary use is as an administration and system information tool. It provides an extension to the functionality of the ”ps” command. • It makes it easy to find an errand process and ”kill” that process. It also has an interactive interface whereby options can be passed while the command is actually running. All in all, a very useful tool.

30-b

top
9:16am up 13 days, 8:05, 8 users, load average: 0.05, 0.05, 0.00 86 processes: 84 sleeping, 1 running, 1 zombie, 0 stopped CPU states: 2.3% user, 0.7% system, 0.0% nice, 96.8% idle Mem: 900236K av, 546472K used, 353764K free, 0K shrd, 37552K buff 190764K cached Swap: 329324K av, 34784K used, 294540K free PID 10281 12547 10284 12173 12543 1 2 USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top geoff 12 0 3012 2568 1352 S 0 0.7 0.2 50:49 enlight geoff 10 0 9340 9340 3768 S 0 0.3 1.0 0:11 emacs geoff 9 0 3328 3328 2072 S 0 0.1 0.3 0:00 Eterm root 9 0 116 72 52 S 0 0.0 0.0 0:19 init root 9 0 0 0 0 SW 0 0.0 0.0 0:01 keventd

31

top’s basic command line options
Note: dashes not required. -b Batch mode. Useful for sending output from top to other programs or to a file. Output is plain text. -d Delay between screen updates. (default 5 seconds) -i Start top ignoring any idle or zombie processes. -p Monitor only processes with given process id. (x20) -q This causes top to refresh without any delay.

32

top’s upper screen
9:16am up 13 days, 8:05, 8 users, load average: 0.05, 0.05, 0.00 86 processes: 84 sleeping, 1 running, 1 zombie, 0 stopped CPU states: 2.3% user, 0.7% system, 0.0% nice, 96.8% idle Mem: 900236K av, 546472K used, 353764K free, 0K shrd, 37552K buff 190764K cached Swap: 329324K av, 34784K used, 294540K free

33

top’s upper screen
9:16am up 13 days, 8:05, 8 users, load average: 0.05, 0.05, 0.00 86 processes: 84 sleeping, 1 running, 1 zombie, 0 stopped CPU states: 2.3% user, 0.7% system, 0.0% nice, 96.8% idle Mem: 900236K av, 546472K used, 353764K free, 0K shrd, 37552K buff 190764K cached Swap: 329324K av, 34784K used, 294540K free • The current system time:

33-a

top’s upper screen
9:16am up 13 days, 8:05, 8 users, load average: 0.05, 0.05, 0.00 86 processes: 84 sleeping, 1 running, 1 zombie, 0 stopped CPU states: 2.3% user, 0.7% system, 0.0% nice, 96.8% idle Mem: 900236K av, 546472K used, 353764K free, 0K shrd, 37552K buff 190764K cached Swap: 329324K av, 34784K used, 294540K free • The current system time: • The ”up time” of the system:

33-b

top’s upper screen
9:16am up 13 days, 8:05, 8 users, load average: 0.05, 0.05, 0.00 86 processes: 84 sleeping, 1 running, 1 zombie, 0 stopped CPU states: 2.3% user, 0.7% system, 0.0% nice, 96.8% idle Mem: 900236K av, 546472K used, 353764K free, 0K shrd, 37552K buff 190764K cached Swap: 329324K av, 34784K used, 294540K free • The current system time: • The ”up time” of the system: • How many users are logged in.

33-c

top’s upper screen
9:16am up 13 days, 8:05, 8 users, load average: 0.05, 0.05, 0.00 86 processes: 84 sleeping, 1 running, 1 zombie, 0 stopped CPU states: 2.3% user, 0.7% system, 0.0% nice, 96.8% idle Mem: 900236K av, 546472K used, 353764K free, 0K shrd, 37552K buff 190764K cached Swap: 329324K av, 34784K used, 294540K free • The current system time: • The ”up time” of the system: • How many users are logged in. • The ”load average” : the average number of processes ready to run over the last 1,5 and 15 minutes

33-d

top’s upper screen
9:16am up 13 days, 8:05, 8 users, load average: 0.05, 0.05, 0.00 86 processes: 84 sleeping, 1 running, 1 zombie, 0 stopped CPU states: 2.3% user, 0.7% system, 0.0% nice, 96.8% idle Mem: 900236K av, 546472K used, 353764K free, 0K shrd, 37552K buff 190764K cached Swap: 329324K av, 34784K used, 294540K free • The current system time: • The ”up time” of the system: • How many users are logged in. • The ”load average” : the average number of processes ready to run over the last 1,5 and 15 minutes • ”CPU States” shows the percentage of CPU time spent in usermode, system mode and at idle.

33-e

top’s upper screen
9:16am up 13 days, 8:05, 8 users, load average: 0.05, 0.05, 0.00 86 processes: 84 sleeping, 1 running, 1 zombie, 0 stopped CPU states: 2.3% user, 0.7% system, 0.0% nice, 96.8% idle Mem: 900236K av, 546472K used, 353764K free, 0K shrd, 37552K buff 190764K cached Swap: 329324K av, 34784K used, 294540K free • The current system time: • The ”up time” of the system: • How many users are logged in. • The ”load average” : the average number of processes ready to run over the last 1,5 and 15 minutes • ”CPU States” shows the percentage of CPU time spent in usermode, system mode and at idle. • ”MEM” shows a complete set of statistics on current memory usage.

33-f

top’s upper screen
9:16am up 13 days, 8:05, 8 users, load average: 0.05, 0.05, 0.00 86 processes: 84 sleeping, 1 running, 1 zombie, 0 stopped CPU states: 2.3% user, 0.7% system, 0.0% nice, 96.8% idle Mem: 900236K av, 546472K used, 353764K free, 0K shrd, 37552K buff 190764K cached Swap: 329324K av, 34784K used, 294540K free • The current system time: • The ”up time” of the system: • How many users are logged in. • The ”load average” : the average number of processes ready to run over the last 1,5 and 15 minutes • ”CPU States” shows the percentage of CPU time spent in usermode, system mode and at idle. • ”MEM” shows a complete set of statistics on current memory usage. • ”SWAP” gives us the same details as ”MEM” but for the swap space.

33-g

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top

ctd. . .

34

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top PID The process ID of each task.

ctd. . .

34-a

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top PID The process ID of each task. USER The user name of the task’s owner.

ctd. . .

34-b

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top PID The process ID of each task. USER The user name of the task’s owner. PRI The priority of the task.

ctd. . .

34-c

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top PID The process ID of each task. USER The user name of the task’s owner. PRI The priority of the task. NI The nice value of the task. Negative nice values are higher priority.

ctd. . .

34-d

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top PID The process ID of each task. USER The user name of the task’s owner. PRI The priority of the task. NI The nice value of the task. Negative nice values are higher priority. SIZE The size of the task’s code plus data plus stack space, in kilobytes, is shown here.

ctd. . .

34-e

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top PID The process ID of each task. USER The user name of the task’s owner. PRI The priority of the task. NI The nice value of the task. Negative nice values are higher priority. SIZE The size of the task’s code plus data plus stack space, in kilobytes, is shown here. RSS The total amount of physical memory used by the task,in kilobytes, is shown here. For ELF processes used library pages are counted here, for a.out processes not.

ctd. . .

34-f

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top PID The process ID of each task. USER The user name of the task’s owner. PRI The priority of the task. NI The nice value of the task. Negative nice values are higher priority. SIZE The size of the task’s code plus data plus stack space, in kilobytes, is shown here. RSS The total amount of physical memory used by the task,in kilobytes, is shown here. For ELF processes used library pages are counted here, for a.out processes not. SHARE The amount of shared memory used by the task is shown in this column. ctd. . .

34-g

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top

35

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top STAT The state of the task is shown here. The state is either S sleeping D uninterruptible sleep R running Z zombies T stopped or trace These states are modified by trailing < for a process with negative nice value, N for a process with positive nice value, W for a swapped out process (this does not work correctly for kernel processes).

35-a

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top STAT The state of the task is shown here. The state is either S sleeping D uninterruptible sleep R running Z zombies T stopped or trace These states are modified by trailing < for a process with negative nice value, N for a process with positive nice value, W for a swapped out process (this does not work correctly for kernel processes). %CPU The task’s share of the CPU time since the last screen update, expressed as a percentage of total CPU time per processor.

35-b

top’s lower screen
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 10281 root 16 -10 97952 6452 1584 S < 0 3.9 0.7 56:57 X 12547 geoff 16 0 1728 1728 764 R 0 0.9 0.1 0:01 top STAT The state of the task is shown here. The state is either S sleeping D uninterruptible sleep R running Z zombies T stopped or trace These states are modified by trailing < for a process with negative nice value, N for a process with positive nice value, W for a swapped out process (this does not work correctly for kernel processes). %CPU The task’s share of the CPU time since the last screen update, expressed as a percentage of total CPU time per processor. %MEM The task’s share of the physical memory.

35-c

top: selected interactive commands
ˆL Redraw the screen

36

top: selected interactive commands
ˆL Redraw the screen f|F Add and remove fields

36-a

top: selected interactive commands
ˆL Redraw the screen f|F Add and remove fields h|? Displays a help screen

36-b

top: selected interactive commands
ˆL Redraw the screen f|F Add and remove fields h|? Displays a help screen S Toggle cumulative mode

36-c

top: selected interactive commands
ˆL Redraw the screen f|F Add and remove fields h|? Displays a help screen S Toggle cumulative mode I Toggle between Irix and Solaris views (SMP-only)

36-d

top: selected interactive commands
ˆL Redraw the screen f|F Add and remove fields h|? Displays a help screen S Toggle cumulative mode I Toggle between Irix and Solaris views (SMP-only) k Kill a task (with any signal)

36-e

top: selected interactive commands
ˆL Redraw the screen f|F Add and remove fields h|? Displays a help screen S Toggle cumulative mode I Toggle between Irix and Solaris views (SMP-only) k Kill a task (with any signal) r Renice a task

36-f

top: selected interactive commands
ˆL Redraw the screen f|F Add and remove fields h|? Displays a help screen S Toggle cumulative mode I Toggle between Irix and Solaris views (SMP-only) k Kill a task (with any signal) r Renice a task T Sort by time / cumulative time

36-g

top: selected interactive commands
ˆL Redraw the screen f|F Add and remove fields h|? Displays a help screen S Toggle cumulative mode I Toggle between Irix and Solaris views (SMP-only) k Kill a task (with any signal) r Renice a task T Sort by time / cumulative time s Set the delay in seconds between updates

36-h

top: selected interactive commands
ˆL Redraw the screen f|F Add and remove fields h|? Displays a help screen S Toggle cumulative mode I Toggle between Irix and Solaris views (SMP-only) k Kill a task (with any signal) r Renice a task T Sort by time / cumulative time s Set the delay in seconds between updates q Quit

36-i

top’s interactive commands
space Update display ˆL Redraw the screen f|F Add and remove fields o|O Change order of displayed fields h|? Displays a help screen S Toggle cumulative mode i Toggle display of idle processes I Toggle between Irix and Solaris views (SMP-only) c Toggle display of command name/line l Toggle display of load average m Toggle display of memory information t Toggle display of summary information

37

k Kill a task (with any signal) r Renice a task N Sort by pid (Numerically) A Sort by age P Sort by CPU usage M Sort by resident memory usage T Sort by time / cumulative time u Show only a specific user n|# Set the number of process to show s Set the delay in seconds between updates W Write configuration file /.toprc q Quit

38

˜/.toprc
$ cat toprc ← AbcDgHIjklMnoTP|qrsuzyV{EFWx 2

39

Killing Processes

40

Job Control
There are three commands and a pretzel used for job control. • jobs • fg • bg •&

41

Job Control
There are three commands and a pretzel used for job control. • jobs • fg • bg •& They are bash built-ins: $ type jobs fg bg ← jobs is a shell builtin fg is a shell builtin bg is a shell builtin For more information, see the Job Control section of man bash.

41-a

&— Direct the shell to execute a command in the background.
Example: $ xeyes ← Notice the xeyes process is started in the foreground and you have no prompt. The user is locked out of further interaction with the shell until a process is stopped, terminated or completed. Now start the xeyes process in the background. $ xeyes & ← [1] 1650 $ Two numbers are listed and the prompt is now also displayed waiting for another command.

42

Job Control
$ xeyes & ← [1] 1650 $

43

Job Control
$ xeyes & ← [1] 1650 $ • The [1] is the programs job id, a unique number for the shell starting from 1.

43-a

Job Control
$ xeyes & ← [1] 1650 $ • The [1] is the programs job id, a unique number for the shell starting from 1. • The 1650 is the process id (pid), which identifies the process across the entire system.

43-b

Job Control
$ xeyes & ← [1] 1650 $ • The [1] is the programs job id, a unique number for the shell starting from 1. • The 1650 is the process id (pid), which identifies the process across the entire system. • Either of these numbers can be used to interact with the program through bash.

43-c

Background Processing
The best candidates for background processing are programs that do not require user input, as these programs will keep on waiting until input is provided. Programs that send their results to standard output (The screen), will do so even if running in the background. If the user is performing another operation, the results may be difficult to interpret. The output from these processes can be redirected to a file. $ wc bigfile > bigfile.wc & ← [1] 1654 $

44

The jobs command

45

The jobs command
$ jobs ← : Lists all commands stopped, or running in the background.

45-a

The jobs command
$ jobs ← : Lists all commands stopped, or running in the background. Options : -l List pid

45-b

The jobs command
$ jobs ← : Lists all commands stopped, or running in the background. Options : -l List pid Example : Start some processes in the background and suspend a foreground process. $ jobs ← [1]+ Stopped [2]- Running $ less job_control.txt xeyes &

45-c

The fg command
$ fg ← : Shell built-in used to force a suspended or background process to continue running in the foreground.

46

The fg command
$ fg ← : Shell built-in used to force a suspended or background process to continue running in the foreground. Example : • Use the ’jobs’ command to find job id. $ jobs ← [1]+ Stopped [2]- Running $ less job_control.txt xeyes &

46-a

The fg command
$ fg ← : Shell built-in used to force a suspended or background process to continue running in the foreground. Example : • Use the ’jobs’ command to find job id. $ jobs ← [1]+ Stopped [2]- Running $ • Use fg to bring xeyes to foreground. $ fg 2 ← xeyes less job_control.txt xeyes &

46-b

The fg command
$ fg ← : Shell built-in used to force a suspended or background process to continue running in the foreground. Example : • Use the ’jobs’ command to find job id. $ jobs ← [1]+ Stopped [2]- Running $ • Use fg to bring xeyes to foreground. $ fg 2 ← xeyes • A % used with the job id is equivalent to fg 2. $ %2 ← xeyes less job_control.txt xeyes &

46-c

The fg command
A job can also be referred to by a string that uniquely identifies the beginning of the command line used to start a job. A ’%’ can also be used with a unique string. $ fg x ← xeyes or $ %x ← xeyes If fg is issued without any argument, the job with the ’+’ in the job list is brought to the foreground. $ fg ← xeyes

47

The bg command
$ bg ← : Used to force a suspended process to continue running in the background.

Job 1 shows the ’find’ command was started in the foreground and then suspended.To start ’find’ in the background, use the ’bg’ command or ’%’.

48

The bg command
$ bg ← : Used to force a suspended process to continue running in the background. Example : Use the ’jobs’ command to find job id. $ jobs ← [1]- Stopped [2]+ Stopped Running [3] $ find -name myfile >myfile.found less job_control.txt xeyes & (wd: /)

Job 1 shows the ’find’ command was started in the foreground and then suspended.To start ’find’ in the background, use the ’bg’ command or ’%’.

48-a

The bg command
$ bg ← : Used to force a suspended process to continue running in the background. Example : Use the ’jobs’ command to find job id. $ jobs ← [1]- Stopped [2]+ Stopped Running [3] $ find -name myfile >myfile.found less job_control.txt xeyes & (wd: /)

Job 1 shows the ’find’ command was started in the foreground and then suspended.To start ’find’ in the background, use the ’bg’ command or ’%’. Example : $ bg 1 ← or $ bg f ← or $ %1 & ← or $ %f & ←

48-b

The End

49