Возникла необходимость мониторинга сервера на Linux? Большинство систем на Linux изначально содержат необходимые утилиты мониторинга, позволяющие получить основные показатели работы системы. Большинства этих утилит достаточно чтоб определись и устранить основные проблемы производительности системы. В этой статье мы рассмотрим основные проблемы работоспособности системы, такие как:

  1. Поиск и устранение узких мест.
  2. Проблемы быстродействия дисков, дисковых массивов и RAID контроллеров.
  3. Проблемы использования CPU
  4. Проблемы использования памяти.
  5. Узкие места сети.

Утилита top - запущенные процессы и использование памяти

top показывает динамические показатели работы системы в реальном времени. По умолчанию она показывает наиболее ресурсоемкие по  CPU процессы и обновляет список каждые 5 секунд.

Часто используемые хоткеи утилиты top:

Hot Key назначение
t включение и выключение суммарной информации
m включение и выключение отображения информации об использовании памяти
A Сортирует на экране пользователей различных системных ресурсов.
f Вход в интерактивный настройщик отображения списка процессов.
o Управляет сортировкой процессов.
r Принудительно обновляет содержимое.
k Выполняет команду kill
z включает и выключает цвета для отображения списка

vmstat - системная активность, информация об оборудовании и системе

Команда vmstat показывает информацию о процессах, памяти, вваде-выводе, трапсах, активности CPU.

Получить информацию об использовании памяти

# vmstat -m

Получить информацию об активных и неактивных страницах памяти

# vmstat -a 

w - получить информацию о залогинившихся пользователях и их действиях

Команда w показыавет информацию о залогинившихся пользователях системы и запущенных ими процессах

# w username
 17:58:47 up 5 days, 20:28, 2 users, load average: 0.36, 0.26, 0.24 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT root pts/0 10.1.3.145 14:55 5.00s 0.04s 0.02s vim /etc/resolv.conf root pts/1 10.1.3.145 17:43 0.00s 0.03s 0.00s w 

uptime - показывает время работы системы

Команда uptime для определения как долго сервер запущен. Сколько времени сейчас, сколько времени сервер работает, сколько пользователей залогинено, показатели load averages для прошедших 1, 5, и 15 минут.

# uptime
 18:02:41 up 41 days, 23:42, 1 user, load average: 0.00, 0.00, 0.00 

1 can be considered as optimal load value. The load can change from system to system. For a single CPU system 1 - 3 and SMP systems 6-10 load value might be acceptable.

ps - показывает системные процессы Linux

ps command will report a snapshot of the current processes. To select all processes use the -A or -e option: # ps -A Sample Outputs:

 PID TTY TIME CMD 1 ? 00:00:02 init 2 ? 00:00:02 migration/0 3 ? 00:00:01 ksoftirqd/0 4 ? 00:00:00 watchdog/0 5 ? 00:00:00 migration/1 6 ? 00:00:15 ksoftirqd/1 .... ..... 4881 ? 00:53:28 java 4885 tty1 00:00:00 mingetty 4886 tty2 00:00:00 mingetty 4887 tty3 00:00:00 mingetty 4888 tty4 00:00:00 mingetty 4891 tty5 00:00:00 mingetty 4892 tty6 00:00:00 mingetty 4893 ttyS1 00:00:00 agetty 12853 ? 00:00:00 cifsoplockd 12854 ? 00:00:00 cifsdnotifyd 14231 ? 00:10:34 lighttpd 14232 ? 00:00:00 php-cgi 54981 pts/0 00:00:00 vim 55465 ? 00:00:00 php-cgi 55546 ? 00:00:00 bind9-snmp-stat 55704 pts/1 00:00:00 ps 

ps is just like top but provides more information.

Show Long Format Output

# ps -Al To turn on extra full mode (it will show command line arguments passed to process): # ps -AlF

To See Threads ( LWP and NLWP)

# ps -AlFH

To See Threads After Processes

# ps -AlLm

Print All Process On The Server

# ps ax # ps axu

Print A Process Tree

# ps -ejH # ps axjf # pstree

Print Security Information

# ps -eo euser,ruser,suser,fuser,f,comm,label # ps axZ # ps -eM

See Every Process Running As User Vivek

# ps -U vivek -u vivek u

Set Output In a User-Defined Format

# ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm # ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm # ps -eopid,tt,user,fname,tmout,f,wchan

Display Only The Process IDs of Lighttpd

# ps -C lighttpd -o pid= OR # pgrep lighttpd OR # pgrep -u vivek php-cgi

Display The Name of PID 55977

# ps -p 55977 -o comm=

Find Out The Top 10 Memory Consuming Process

# ps -auxf | sort -nr -k 4 | head -10

Find Out top 10 CPU Consuming Process

# ps -auxf | sort -nr -k 3 | head -10

#6: free - Memory Usage

The command free displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel. # free Sample Output:

 total used free shared buffers cached Mem: 12302896 9739664 2563232 0 523124 5154740 -/+ buffers/cache: 4061800 8241096 Swap: 1052248 0 1052248 

iostat - средняя загрузка CPU, активность дисков

The command iostat report Central Processing Unit (CPU) statistics and input/output statistics for devices, partitions and network filesystems (NFS). # iostat Sample Outputs:

Linux 2.6.18-128.1.14.el5 (www03.nixcraft.in) 06/26/2009 avg-cpu: %user %nice %system %iowait %steal %idle 3.50 0.09 0.51 0.03 0.00 95.86 Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn sda 22.04 31.88 512.03 16193351 260102868 sda1 0.00 0.00 0.00 2166 180 sda2 22.04 31.87 512.03 16189010 260102688 sda3 0.00 0.00 0.00 1615 0 

sar - Collect and Report System Activity

The sar command is used to collect, report, and save system activity information. To see network counter, enter: # sar -n DEV | more To display the network counters from the 24th: # sar -n DEV -f /var/log/sa/sa24 | more You can also display real time usage using sar: # sar 4 5 Sample Outputs:

Linux 2.6.18-128.1.14.el5 (www03.nixcraft.in) 06/26/2009 06:45:12 PM CPU %user %nice %system %iowait %steal %idle 06:45:16 PM all 2.00 0.00 0.22 0.00 0.00 97.78 06:45:20 PM all 2.07 0.00 0.38 0.03 0.00 97.52 06:45:24 PM all 0.94 0.00 0.28 0.00 0.00 98.78 06:45:28 PM all 1.56 0.00 0.22 0.00 0.00 98.22 06:45:32 PM all 3.53 0.00 0.25 0.03 0.00 96.19 Average: all 2.02 0.00 0.27 0.01 0.00 97.70 

mpstat - использование мультипроцессорности

The mpstat command displays activities for each available processor, processor 0 being the first one. mpstat -P ALL to display average CPU utilization per processor: # mpstat -P ALL Sample Output:

Linux 2.6.18-128.1.14.el5 (www03.nixcraft.in) 06/26/2009 06:48:11 PM CPU %user %nice %sys %iowait %irq %soft %steal %idle intr/s 06:48:11 PM all 3.50 0.09 0.34 0.03 0.01 0.17 0.00 95.86 1218.04 06:48:11 PM 0 3.44 0.08 0.31 0.02 0.00 0.12 0.00 96.04 1000.31 06:48:11 PM 1 3.10 0.08 0.32 0.09 0.02 0.11 0.00 96.28 34.93 06:48:11 PM 2 4.16 0.11 0.36 0.02 0.00 0.11 0.00 95.25 0.00 06:48:11 PM 3 3.77 0.11 0.38 0.03 0.01 0.24 0.00 95.46 44.80 06:48:11 PM 4 2.96 0.07 0.29 0.04 0.02 0.10 0.00 96.52 25.91 06:48:11 PM 5 3.26 0.08 0.28 0.03 0.01 0.10 0.00 96.23 14.98 06:48:11 PM 6 4.00 0.10 0.34 0.01 0.00 0.13 0.00 95.42 3.75 06:48:11 PM 7 3.30 0.11 0.39 0.03 0.01 0.46 0.00 95.69 76.89 

pmap - использование памяти процессами

The command pmap report memory map of a process. Use this command to find out causes of memory bottlenecks. # pmap -d PID To display process memory information for pid # 47394, enter: # pmap -d 47394 Sample Outputs:

47394: /usr/bin/php-cgi Address Kbytes Mode Offset Device Mapping 0000000000400000 2584 r-x-- 0000000000000000 008:00002 php-cgi 0000000000886000 140 rw--- 0000000000286000 008:00002 php-cgi 00000000008a9000 52 rw--- 00000000008a9000 000:00000 [ anon ] 0000000000aa8000 76 rw--- 00000000002a8000 008:00002 php-cgi 000000000f678000 1980 rw--- 000000000f678000 000:00000 [ anon ] 000000314a600000 112 r-x-- 0000000000000000 008:00002 ld-2.5.so 000000314a81b000 4 r---- 000000000001b000 008:00002 ld-2.5.so 000000314a81c000 4 rw--- 000000000001c000 008:00002 ld-2.5.so 000000314aa00000 1328 r-x-- 0000000000000000 008:00002 libc-2.5.so 000000314ab4c000 2048 ----- 000000000014c000 008:00002 libc-2.5.so ..... ...... .. 00002af8d48fd000 4 rw--- 0000000000006000 008:00002 xsl.so 00002af8d490c000 40 r-x-- 0000000000000000 008:00002 libnss_files-2.5.so 00002af8d4916000 2044 ----- 000000000000a000 008:00002 libnss_files-2.5.so 00002af8d4b15000 4 r---- 0000000000009000 008:00002 libnss_files-2.5.so 00002af8d4b16000 4 rw--- 000000000000a000 008:00002 libnss_files-2.5.so 00002af8d4b17000 768000 rw-s- 0000000000000000 000:00009 zero (deleted) 00007fffc95fe000 84 rw--- 00007ffffffea000 000:00000 [ stack ] ffffffffff600000 8192 ----- 0000000000000000 000:00000 [ anon ] mapped: 933712K writeable/private: 4304K shared: 768000K 

The last line is very important:

  • mapped: 933712K total amount of memory mapped to files
  • writeable/private: 4304K the amount of private address space
  • shared: 768000K the amount of address space this process is sharing with others

#11 and #12: netstat and ss - Network Statistics

The command netstat displays network connections, routing tables, interface statistics, masquerade connections, and multicast memberships. ss command is used to dump socket statistics. It allows showing information similar to netstat. See the following resources about ss and netstat commands:

#13: iptraf - Real-time Network Statistics

The iptraf command is interactive colorful IP LAN monitor. It is an ncurses-based IP LAN monitor that generates various network statistics including TCP info, UDP counts, ICMP and OSPF information, Ethernet load info, node stats, IP checksum errors, and others. It can provide the following info in easy to read format:

  • Network traffic statistics by TCP connection
  • IP traffic statistics by network interface
  • Network traffic statistics by protocol
  • Network traffic statistics by TCP/UDP port and by packet size
  • Network traffic statistics by Layer2 address

Fig.02: General interface statistics: IP traffic statistics by network interface

Fig.03 Network traffic statistics by TCP connection

#14: tcpdump - Detailed Network Traffic Analysis

The tcpdump is simple command that dump traffic on a network. However, you need good understanding of TCP/IP protocol to utilize this tool. For.e.g to display traffic info about DNS, enter: # tcpdump -i eth1 'udp port 53' To display all IPv4 HTTP packets to and from port 80, i.e. print only packets that contain data, not, for example, SYN and FIN packets and ACK-only packets, enter: # tcpdump 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' To display all FTP session to 202.54.1.5, enter: # tcpdump -i eth1 'dst 202.54.1.5 and (port 21 or 20' To display all HTTP session to 192.168.1.5: # tcpdump -ni eth0 'dst 192.168.1.5 and tcp and port http' Use wireshark to view detailed information about files, enter: # tcpdump -n -i eth1 -s 0 -w output.txt src or dst port 80

#15: strace - System Calls

Trace system calls and signals. This is useful for debugging webserver and other server problems. See how to use to trace the process and see What it is doing.

#16: /Proc file system - Various Kernel Statistics

/proc file system provides detailed information about various hardware devices and other Linux kernel information. See Linux kernel /proc documentations for further details. Common /proc examples: # cat /proc/cpuinfo # cat /proc/meminfo # cat /proc/zoneinfo # cat /proc/mounts

17#: Nagios - Server And Network Monitoring

Nagios is a popular open source computer system and network monitoring application software. You can easily monitor all your hosts, network equipment and services. It can send alert when things go wrong and again when they get better. FAN is "Fully Automated Nagios". FAN goals are to provide a Nagios installation including most tools provided by the Nagios Community. FAN provides a CDRom image in the standard ISO format, making it easy to easilly install a Nagios server. Added to this, a wide bunch of tools are including to the distribution, in order to improve the user experience around Nagios.

18#: Cacti - Web-based Monitoring Tool

Cacti is a complete network graphing solution designed to harness the power of RRDTool's data storage and graphing functionality. Cacti provides a fast poller, advanced graph templating, multiple data acquisition methods, and user management features out of the box. All of this is wrapped in an intuitive, easy to use interface that makes sense for LAN-sized installations up to complex networks with hundreds of devices. It can provide data about network, CPU, memory, logged in users, Apache, DNS servers and much more. See how to install and configure Cacti network graphing tool under CentOS / RHEL.

#19: KDE System Guard - Real-time Systems Reporting and Graphing

KSysguard is a network enabled task and system monitor application for KDE desktop. This tool can be run over ssh session. It provides lots of features such as a client/server architecture that enables monitoring of local and remote hosts. The graphical front end uses so-called sensors to retrieve the information it displays. A sensor can return simple values or more complex information like tables. For each type of information, one or more displays are provided. Displays are organized in worksheets that can be saved and loaded independently from each other. So, KSysguard is not only a simple task manager but also a very powerful tool to control large server farms.

Fig.05 KDE System Guard {Image credit: Wikipedia}

See the KSysguard handbook for detailed usage.

#20: Gnome System Monitor - Real-time Systems Reporting and Graphing

The System Monitor application enables you to display basic system information and monitor system processes, usage of system resources, and file systems. You can also use System Monitor to modify the behavior of your system. Although not as powerful as the KDE System Guard, it provides the basic information which may be useful for new users:

  • Displays various basic information about the computer's hardware and software.
  • Linux Kernel version
  • GNOME version
  • Hardware
  • Installed memory
  • Processors and speeds
  • System Status
  • Currently available disk space
  • Processes
  • Memory and swap space
  • Network usage
  • File Systems
  • Lists all mounted filesystems along with basic information about each.

Fig.06 The Gnome System Monitor application

Bonus: Additional Tools

A few more tools:

  • nmap - scan your server for open ports.
  • lsof - list open files, network connections and much more.
  • ntop web based tool - ntop is the best tool to see network usage in a way similar to what top command does for processes i.e. it is network traffic monitoring software. You can see network status, protocol wise distribution of traffic for UDP, TCP, DNS, HTTP and other protocols.
  • Conky - Another good monitoring tool for the X Window System. It is highly configurable and is able to monitor many system variables including the status of the CPU, memory, swap space, disk storage, temperatures, processes, network interfaces, battery power, system messages, e-mail inboxes etc.
  • GKrellM - It can be used to monitor the status of CPUs, main memory, hard disks, network interfaces, local and remote mailboxes, and many other things.
  • vnstat - vnStat is a console-based network traffic monitor. It keeps a log of hourly, daily and monthly network traffic for the selected interface(s).
  • htop - htop is an enhanced version of top, the interactive process viewer, which can display the list of processes in a tree form.
  • mtr - mtr combines the functionality of the traceroute and ping programs in a single network diagnostic tool.

Did I miss something? Please add your favorite system motoring tool in the comments.