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For every Linux Admin it is very tough job to monitor and debug Linux system performance problem every day. In this article I will show you top 10 frequently used command line monitoring tools that might be useful for you.
1. Top – Linux Process Monitoring
Top command is used to monitor Linux Performance. Top command used to display all the running and active real time process. It display CPU Usage, Memory Status, Swap Usage, Check Size, Buffer Size, Process PID, User, Command and much more. Using this command you can also check memory and cpu utilization of running process.
# top
top - 19:30:38 up 783 days, 5:36, 0 users, load average: 0.06, 0.03, 0.00
Tasks: 91 total, 1 running, 90 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 2764752k total, 423272k used, 2341480k free, 0k buffers
Swap: 5529504k total, 263764k used, 5265740k free, 114912k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 20 0 21328 200 84 S 0.0 0.0 1:14.62 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd/145172
3 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khelper/145172
4 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/145172/0
5 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/145172/1
6 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/145172/2
7 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/145172/3
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/145172/4
9 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/145172/5
10 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/145172/6
11 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rpciod/145172/7
12 root 20 0 0 0 0 S 0.0 0.0 0:00.00 nfsiod/145172
136 root 16 -4 10680 4 0 S 0.0 0.0 0:00.02 udevd
483 root 20 0 244m 5072 400 S 0.0 0.2 26:11.69 rsyslogd
736 root 20 0 135m 3680 652 S 0.0 0.1 40:34.74 munin-node
967 root 20 0 4068 8 4 S 0.0 0.0 0:00.00 mingetty
997 root 20 0 4068 8 4 S 0.0 0.0 0:00.00 mingetty
2583 root 20 0 103m 8 4 S 0.0 0.0 0:00.00 inotifywait.sh
2584 root 20 0 25720 18m 228 S 0.0 0.7 0:17.36 inotifywait
2. VmStat – Virtual Memory Statistics
VmStat command used to monitor virtual memory, kernal threada, disk, system process, etc.. By default it is not installed on the system, you will need to install package called sysstat which include vmstat program.
# vmstat procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 0 0 263764 2341680 0 114912 0 0 0 1 0 0 1 0 99 0 0
3. Losf – List Open Files
Lsof command used to display list of all the open files and process. Open files include are network socket, disk files, pipes, devices and processes. Main use of this command is when a disk con not be unmounted and displays the error that files are being used or opened. Using this command you can easily identify which files are in use.
# lsof COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME init 1 root cwd DIR 0,39 4096 2501026 / init 1 root rtd DIR 0,39 4096 2501026 / init 1 root txt REG 0,39 150352 2495060 (deleted)/sbin/init init 1 root mem REG 253,1 2513643 (deleted)/lib64/libnss_ldap.so.2 (stat: No such file or directory) init 1 root mem REG 253,1 2503526 (deleted)/lib64/libnss_files-2.12.so (stat: No such file or directory) init 1 root mem REG 253,1 2501184 (deleted)/lib64/libc-2.12.so (stat: No such file or directory) init 1 root mem REG 253,1 2501476 (deleted)/lib64/libgcc_s-4.4.7-20120601.so.1;55e556dd (stat: No such file or directory) init 1 root mem REG 253,1 2503555 (deleted)/lib64/librt-2.12.so (stat: No such file or directory) init 1 root mem REG 253,1 2501134 (deleted)/lib64/libpthread-2.12.so (stat: No such file or directory) init 1 root mem REG 253,1 2501158 (deleted)/lib64/libdbus-1.so.3.4.0 (stat: No such file or directory) init 1 root mem REG 253,1 2501227 /lib64/libnih-dbus.so.1.0.0 (path dev=0,39) init 1 root mem REG 253,1 2501248 /lib64/libnih.so.1.0.0 (path dev=0,39) init 1 root mem REG 253,1 2501673 (deleted)/lib64/ld-2.12.so (stat: No such file or directory) init 1 root mem REG 253,1 2495060 (deleted)/sbin/init (stat: No such file or directory) init 1 root 0u CHR 1,3 0t0 2501528 /dev/null init 1 root 1u CHR 1,3 0t0 2501528 /dev/null init 1 root 2u CHR 1,3 0t0 2501528 /dev/null init 1 root 3r FIFO 0,8 0t0 1485165868 pipe init 1 root 4w FIFO 0,8 0t0 1485165868 pipe init 1 root 5r DIR 0,10 0 1 inotify init 1 root 6r DIR 0,10 0 1 inotify init 1 root 7u unix 0xffff88023c4c4e40 0t0 1485165870 @/com/ubuntu/upstart
4. Tcpdump – Network Packet Analyzer
Tcpdump used to analyze network packet or it is also packet sniffer program that is used filter TCP/IP packets that received or transferred on a specific interface over a network.
# tcpdump -i venet0:0 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on venet0:0, link-type LINUX_SLL (Linux cooked), capture size 65535 bytes 19:35:33.847554 IP www.looklinux.com.sicct > ldap01.ldap: Flags [P.], seq 3454527163:3454527261, ack 1861271793, win 1731, length 98 19:35:33.878878 IP ldap01.ldap > www.looklinux.com.sicct: Flags [P.], seq 1:17, ack 98, win 126, length 16 19:35:33.878893 IP www.looklinux.com.sicct > ldap01.ldap: Flags [.], ack 17, win 1731, length 0 19:35:33.878959 IP www.looklinux.com.sicct > ldap01.ldap: Flags [P.], seq 98:251, ack 17, win 1731, length 153 19:35:33.910485 IP ldap01.ldap > www.looklinux.com.sicct: Flags [P.], seq 17:33, ack 251, win 126, length 16 19:35:33.911363 IP www.looklinux.com.31237 > ldap01.ldap: Flags [P.], seq 3375107161:3375107280, ack 3164352562, win 1750, length 119 19:35:33.942867 IP ldap01.ldap > www.looklinux.com.31237: Flags [P.], seq 1:120, ack 119, win 4150, length 119 19:35:33.942892 IP www.looklinux.com.31237 > ldap01.ldap: Flags [.], ack 120, win 1750, length 0 19:35:33.942873 IP ldap01.ldap > www.looklinux.com.31237: Flags [P.], seq 120:136, ack 119, win 4150, length 16 19:35:33.942909 IP www.looklinux.com.31237 > ldap01.ldap: Flags [.], ack 136, win 1750, length 0 19:35:33.950042 IP www.looklinux.com.sicct > ldap01.ldap: Flags [.], ack 33, win 1731, length 0
5. Netstat – Newtwork Statistics
Netstat is used to monitor incoming and outgoing network packets statistics as well as interface statistics. Mostly it is used to monitor network performance and troubleshot network related issue.
# netstat -a | more Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 *:https *:* LISTEN tcp 0 0 *:down *:* LISTEN tcp 0 0 localhost.locald:cslistener *:* LISTEN tcp 0 0 *:memcache *:* LISTEN tcp 0 0 *:http *:* LISTEN tcp 0 0 *:81 *:* LISTEN tcp 0 0 www.looklinux.com:munin *:* LISTEN tcp 0 0 localhost.localdomain:smtp *:* LISTEN tcp 0 0 www.looklinux.com:sicct ldap:ldap ESTABLISHED tcp 0 0 www.looklinux.com:31936 ldap:ldap ESTABLISHED tcp 0 0 www.looklinux.com:31237 ldap:ldap ESTABLISHED tcp 0 0 www.looklinux.com:http 10.12.145.174:55448 TIME_WAIT tcp 0 0 www.looklinux.com:25575 vsrv:mysql TIME_WAIT tcp 0 0 www.looklinux.com:31215 ldap:ldap ESTABLISHED tcp 0 0 www.looklinux.com:25574 vsrv:mysql TIME_WAIT tcp 0 0 www.looklinux.com:36582 vsrv:mysql TIME_WAIT tcp 0 0 www.looklinux.com:36577 vsrv:mysql TIME_WAIT tcp 0 0 www.looklinux.com:http www.looklinux.com:30355 TIME_WAIT tcp 0 0 www.looklinux.com:http www.looklinux.com:19353 TIME_WAIT tcp 0 0 wwiw.looklinux.com:12227 ldap:ldap ESTABLISHED tcp 0 0 *:memcache *:* LISTEN udp 0 0 *:memcache *:* udp 0 0 *:memcache *:* Active UNIX domain sockets (servers and established)
6. Htop – Monitoring Linux Process
Htop is used to monitor real time Linux process. This is similar to Linux top command but it has some rich features. It is user friendly interface to manage process, shortcut keys, vertical and horizontal view of the processes. By default it does not comes with Linux systems, you need to install it using YUM package manager tool.
7. Iotop – Linux Disk I/O Monitoring
Iotop is used to monitor real time Disk I/O and process. This is much similar to top command and Htop command. This tool is much useful for finding the exact process and high used disk Read/Writes of the processes.
# iotop Total DISK READ: 127.33 K/s | Total DISK WRITE: 0.00 B/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND 2661 be/2 apache 127.33 K/s 3.75 K/s 0.00 % 1.61 % httpd 8532 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 10632 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 12724 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 4540 be/2 apache 0.00 B/s 7.49 K/s 0.00 % 0.00 % httpd 21017 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 21025 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 564 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 23135 be/2 apache 0.00 B/s 7.49 K/s 0.00 % 0.00 % httpd 24827 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 23927 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 15009 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 19141 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 757 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 14480 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 19428 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 19281 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 15189 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 7348 be/2 apache 0.00 B/s 7.49 K/s 0.00 % 0.00 % httpd 27776 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 23770 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd 7400 be/2 apache 0.00 B/s 3.75 K/s 0.00 % 0.00 % httpd
8. lostat – Input/Output Statistics
loStat is used to collect and show system input and output storage device statistics. This is mostly used to trace storage device performance issues including device, remote disks, local disks such as NFS (Network File System).
# iostat
Linux 2.6.32-042stab081.5 (www.looklinux.com) 08/26/2017 _x86_64_ (8 CPU)
avg-cpu: %user %nice %system %iowait %steal %idle
14.13 9.29 1.67 0.60 0.00 74.30
Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdb 120.57 1086.78 3415.39 119123008403 374365353408
sda 118.71 1080.47 3420.61 118431464278 374937409672
md127 0.00 0.00 0.00 12474 159282
md126 0.40 1.92 3.47 210365802 380585504
md125 162.92 227.88 3410.69 24977936773 373850361296
dm-0 0.67 2.13 3.27 233577856 358095816
dm-1 159.99 225.75 3407.43 24744356250 373492265480
9. IPTraf – Monitor Real Time IP LAN
IPTraf is used to monitor real time network (IP LAN) in Linux. It collects lots of information such as IP traffic that passes over the network, with TCP flag information, ICMP details, TCP/UDP traffic breakdowns, TCP connection packet and byne counts.
10. Monit – Monitor Linux Process and Service
Monit is a free open source. It is web based process monitoring utility that automatically monitors and managers system processes, files, programs, directories, permissions, checksums and filesystems. It also monitor services like MySQL, Apache, Mail, FTP, ProFTP, Nginx and many more.
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