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Who's hogging the network? Bandwidth usage on a Linux system

Sandra Henry-Stocker | June 16, 2017
How to get a clear view of network bandwidth usage on a Linux system.

hogs basic sounds
Credit: basic_sounds

There are a lot of reasons why systems slow down.

Some process might be bogging down the CPU, you may be seeing a lot of disk contention, or maybe memory is in high demand and a lot of swapping is going on. Then again, the system may be slowed down because of network bandwidth contention.

Like a busy door with too many people wanting to enter and exit at the same time, a system's network connection can represent a serious limiting factor in how well it performs. That said, if you're looking for good, real-time insights on how a system is using its network bandwidth -- in particular which processes may be using far more than their fair share -- you're going to have a hard time beating nethogs.

 

What is nethogs?

Different than commands such as iftop (for checking bandwidth usage), netstat (for looking at interface statistics), and top (for examining process resource usage as well as CPU and memory usage), the nethogs command provides real-time bandwidth per process statistics that can help you nail down and resolve network interface contention problems.

This open source, command-line tool lets you spot right away what process is responsible when you notice that your network interface is bogged down and you want to pin down what's going on.

 

Getting nethogs

The nethogs tool is very likely already installed on your system. It's included in most Linux distributions today. A quick which nethogs command will let you know for sure. If it isn't installed, a sudo yum install nethogs of sudo apt install nethogs command will quickly set it up for you. As with tools like top, nethogs runs on the command line, but it requires that you use sudo or run as root.

 

Using nethogs

Using nethogs is easy, but there are some options worth looking into.

For one thing, you can have the stats updated less frequently than the default once/second with -d option if you'd like to slow things down a bit.Example:

Example: nethogs -d 5

The -r and -s options allow you to sort by the sent or received values instead of overall bandwidth.

If you have multiple network interfaces and just want to examine one of them, use a command such as nethogs eth0. You can specify more than one interface with this option if you like (e.g., nethogs eth0 eth1). The default is to look at all of them.

The output from nethogs will look something like this:

NetHogs version 0.8.5-2

    PID USER   PROGRAM                    DEV      SENT    RECEIVED
   6245 _apt   ..sr/lib/apt/methods/http  enp0s2    0.977    36.629 KB/sec
   6244 _apt   ..sr/lib/apt/methods/http  enp0s2    0.786    18.305 KB/sec
   6243 _apt   ..sr/lib/apt/methods/http  enp0s2    1.507     3.018 KB/sec
   2837 shs    /usr/lib/firefox/firefox   enp0s2    0.403     0.711 KB/sec
   5949 shs    sshd: shs@pts/2            enp0s2    3.368     0.627 KB/sec
   6183 root   dirmngr                    enp0s2    0.000     0.000 KB/sec
      ? root   ..2.168.0.26:46186-91.189            0.000     0.000 KB/sec
      ? root   ..2.168.0.26:48030-91.189            0.000     0.000 KB/sec
   6169 root   /usr/bin/python3           enp0s2    0.000     0.000 KB/sec
      ? root   unknown TCP                          0.000     0.000 KB/sec

  TOTAL                                             7.040    59.290 KB/sec

 

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