Sysdig: What It Is and How to Use It

Sysdig is a universal system visibility tool with support for containers. What makes Sysdig special, is that it hooks itself into the machine's kernel and segregates the information on a per-container basis.For the scope of this tutorial, we will focus on the open-source version of Sysdig.

In the next sections, you will:

• Install Sysdig
• Spin up a Wordpress installation using docker-compose
• Use Sysdig to collect events and analyze them at a later time
• Use Sysdig to analyze data in real-time

Prerequisites

• Docker is installed on your system. For details about installing Docker, refer to the Install Docker page.
• Docker Compose is installed on your system. Refer to the Install Docker Compose page for instructions about how to install Docker Compose.
• The kernel headers are installed on the host system.

Install Sysdig

Follow these steps to install Sysdig inside a Docker container:

1.In a terminal window, execute the following command to pull the Sysdig Docker image:

docker pull sysdig/sysdig

Using default tag: latest
latest: Pulling from sysdig/sysdig
2967486b0658: Pull complete
78101b780c72: Pull complete
7e78b657334d: Pull complete
650327159ca8: Pull complete
47ebf73ab754: Pull complete
bf51ac76a6d9: Pull complete
0cd11104dbf6: Pull complete
e6dcf17d00d8: Pull complete
230d60083576: Pull complete
fd5ea9faf384: Pull complete
6de86c8ed6e9: Pull complete
8d1825f8be4b: Pull complete
Digest: sha256:bbfe6953fd2b3221a8974eb13024dd33c7e78aebef8fee3d7a0d9ecdeed84ce0
Status: Downloaded newer image for sysdig/sysdig:latest

2.Run Sysdig in a container by entering:

docker run -i -t --name sysdig --privileged -v /var/run/docker.sock:/host/var/run/docker.sock -v /dev:/host/dev -v /proc:/host/proc:ro -v /boot:/host/boot:ro -v /lib/modules:/host/lib/modules:ro -v /usr:/host/usr:ro sysdig/sysdig

* Setting up /usr/src links from host
* Unloading sysdig-probe, if present
* Running dkms install for sysdig
Error! echo
Your kernel headers for kernel 3.10.0-957.12.2.el7.x86_64 cannot be found at
/lib/modules/3.10.0-957.12.2.el7.x86_64/build or /lib/modules/3.10.0-957.12.2.el7.x86_64/source.
* Running dkms build failed, couldn't find /var/lib/dkms/sysdig/0.26.4/build/make.log
* Trying to load a system sysdig-probe, if present
* Trying to find precompiled sysdig-probe for 3.10.0-957.12.2.el7.x86_64
Found kernel config at /host/boot/config-3.10.0-957.12.2.el7.x86_64
* Trying to download precompiled module from https://s3.amazonaws.com/download.draios.com/stable/sysdig-probe-binaries/sysdig-probe-0.26.4-x86_64-3.10.0-957.12.2.el7.x86_64-82e2ae1fb159132636f7b50a762f20ef.ko
Download succeeded, loading module
root@7b14a23f22eb:/#

A few things to note about the above command:

• The -i flag keeps STDIN open.
• The --privileged parameter provides access to all devices on the host. Also it sets SELinux to allow the processes running inside of the container the same access to the host as a process running on the host.
• The -v flag specifies the list of files (on the host) that Sysdig can access.

Spin Up a Wordpress Installation

In this section, you will install Wordpress using the docker-compose command.

1.In a new terminal window, move into your projects directory and type the following commands:

mkdir wordpress-sysdig && cd wordpress-sysdig

2.Create a file called docker-compose with the following content:

version: '3.3'

services:
   db:
     image: mysql:5.7
     volumes:
       - db_data:/var/lib/mysql
     restart: always
     environment:
       MYSQL_ROOT_PASSWORD: somewordpress
       MYSQL_DATABASE: wordpress
       MYSQL_USER: wordpress
       MYSQL_PASSWORD: wordpress

   wordpress:
     depends_on:
       - db
     image: wordpress:latest
     ports:
       - "8000:80"
     restart: always
     environment:
       WORDPRESS_DB_HOST: db:3306
       WORDPRESS_DB_USER: wordpress
       WORDPRESS_DB_PASSWORD: wordpress
       WORDPRESS_DB_NAME: wordpress
volumes:
    db_data: {}

3.Run the docker-compose up command in detached mode with:

docker-compose up -d

Creating network "wordpress-sysdig_default" with the default driver
Creating volume "wordpress-sysdig_db_data" with default driver
Pulling wordpress (wordpress:latest)...
latest: Pulling from library/wordpress
8ec398bc0356: Pull complete
85cf4fc86478: Pull complete
970dadf4ccb6: Pull complete
8c04561117a4: Pull complete
d6b7434b63a2: Pull complete
83d8859e9744: Pull complete
9c3d824d0ad5: Pull complete
9e316fd5b3b3: Pull complete
578b40496c37: Pull complete
814ae7711d3c: Pull complete
4896fed78b6b: Pull complete
e74d71e9611d: Pull complete
46017765526c: Pull complete
280386098458: Pull complete
f32eb0d8c540: Pull complete
5c47b9ea747a: Pull complete
ecda5b7aad12: Pull complete
84256a6b6b44: Pull complete
35d4f385efb7: Pull complete
bf697c2ae701: Pull complete
d054b015f084: Pull complete
Digest: sha256:73e8d8adf491c7a358ff94c74c8ebe35cb5f8857e249eb8ce6062b8576a01465
Status: Downloaded newer image for wordpress:latest
Creating wordpress-sysdig_db_1 ... done
Creating wordpress-sysdig_wordpress_1 ... done

4.You can verify the status of your containers with:

If all is going well, you should see something similar to the following output:

CONTAINER ID        IMAGE               COMMAND                  CREATED              STATUS              PORTS                  NAMES
f390eec29f52        wordpress:latest    "docker-entrypoint.s…"   About a minute ago   Up About a minute   0.0.0.0:8000->80/tcp   wordpress-sysdig_wordpress_1
a844840626d8        mysql:5.7           "docker-entrypoint.s…"   About a minute ago   Up About a minute   3306/tcp, 33060/tcp    wordpress-sysdig_db_1
7b14a23f22eb        sysdig/sysdig       "/docker-entrypoint.…"   13 minutes ago       Up 13 minutes                              sysdig

5.Now Wordpress is up and running. Point your browser to http://localhost:8000 to start the installation wizard:

6.Once the installation wizard is finished, let us go ahead and create a sample post:

Collecting Data to a File

In this section, we'll show how you can use Sysdig to collect events and analyze them at a later time.

1.To dump all captured events to a file, move to the Sysdig container, and enter the following command:

sysdig -w monitoring-wordpress.scap

2.In a new terminal window, use ab to make 10000 requests with a maximum of 100 requests running concurrently:

ab -n 1000 -c 100 http://localhost:8000/?p=7

This is ApacheBench, Version 2.3 <$Revision: 1430300 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking localhost (be patient)
Completed 100 requests
Completed 200 requests
Completed 300 requests
Completed 400 requests
Completed 500 requests
Completed 600 requests
Completed 700 requests
Completed 800 requests
Completed 900 requests
Completed 1000 requests
Finished 1000 requests

Note that the above output was truncated for brevity.

3.Move back to tour Sysdig container and stop capturing data by entering "CTRL+C".

Analyzing data

Now, if you look at the size of the monitoring-wordpress.scap file, you'll notice that Sysdig captured no less than 80M of data:

ls -lh monitoring-wordpress.scap

-rw-r--r--. 1 root root 80M Jan  7 16:28 monitoring-wordpress.scap

To find your way through this mountain of data, you'll use something called a chisel.

A chisel is basically a Lua script that analyzes the event stream and performs useful actions.

You can run the following command to display the list of chisels:

sysdig -cl

Category: Application
---------------------
httplog         HTTP requests log
httptop         Top HTTP requests
memcachelog     memcached requests log

Category: CPU Usage
-------------------
spectrogram     Visualize OS latency in real time.
subsecoffset    Visualize subsecond offset execution time.
topcontainers_cpu
                Top containers by CPU usage
topprocs_cpu    Top processes by CPU usage

Category: Errors
----------------
topcontainers_error
                Top containers by number of errors
topfiles_errors Top files by number of errors
topprocs_errors top processes by number of errors

Note that the above output was truncated for brevity.

To retrieve detailed information about a chisel, run the sysdig command followed by the -i flag and the name of the chisel, as in the following example:

sysdig -i httptop

Category: Application
---------------------
httptop         Top HTTP requests

Show top HTTP requests by: ncalls, time or bytes
Args:
[string] by - Show top HTTP transactions by: ncalls, time or by
                tes, default is ncalls

Continuing our example, here's how you can use the httptop chisel to display the top HTTP requests:

sysdig -r monitoring-wordpress.scap -c httptop

ncalls              method              url
--------------------------------------------------------------------------------
2001                GET                 localhost:8000/?p=7
14                  OPTIONS             *
2                   GET                 localhost:8000/favicon.ico
1                   GET                 /wp-content/themes/twentytwenty/assets/fonts/inter/Inter-upright-var.woff2
1                   GET                 localhost/v1.24/containers/6bd8418eb03f/json
1                   GET                 localhost/v1.24/containers/06def7875617/json
1                   GET                 /v1.24/images/1b1624b63467ec61fab209b6be6e79707ae786df86607b9474b246acd31600
1                   GET                 /v1.24/images/db39680b63ac47a1d989da7b742f7b382af34d85a68214f8977bad59c05901
1                   GET                 localhost:8000/

You can see the same information in a container-friendly format with the -pcontainer flag:

sysdig -r monitoring-wordpress.scap -c httptop -pcontainer

ncalls              container           method              url
--------------------------------------------------------------------------------
1000                wordpress-sysdig_wo GET                 localhost:8000/?p=7
1000                host                GET                 localhost:8000/?p=7
43                  wordpress-sysdig_wo OPTIONS             *
1                   sysdig              GET                 /v1.24/images/1b1624b63467ec61fab209b6be6e79707ae786df86607b9474b246acd31600
1                   sysdig              GET                 localhost/v1.24/containers/06def7875617/json
1                   sysdig              GET                 localhost/v1.24/containers/cd06093b141b/json
1                   sysdig              GET                 /v1.24/images/00e230fe24da9067f9b6e65cfbe9935a5affac1ae8e44edb6a5b0ccc26374d
1                   sysdig              GET                 /v1.24/images/db39680b63ac47a1d989da7b742f7b382af34d85a68214f8977bad59c05901

Digging Deeper

Sysdig captures content-rich information that lets you get detailed insights into the inner-workings of your containers. Let's suppose you're running a few containers and want to know which process consumes the most CPU.

1.List the containers that were active during the period in which you captured events:

sysdig -r monitoring-wordpress.scap -c lscontainers

2.You can identify the container that consumed the most CPU with:

sysdig -r monitoring-wordpress.scap -c topcontainers_cpu

CPU%                container.name
--------------------------------------------------------------------------------
5.37%               wordpress-sysdig_wordpress_1
1.35%               wordpress-sysdig_db_1
0.84%               host
0.51%               sysdig

3.You can dig even deeper and identify the most CPU intensive process with the topprocs_cpu chisel:

sysdig -r monitoring-wordpress.scap -c topprocs_cpu container.name contains wordpress_1

CPU%                Process             PID
--------------------------------------------------------------------------------
0.12%               apache2             8383
0.11%               apache2             9413
0.11%               apache2             9300
0.11%               apache2             9242
0.11%               apache2             8897
0.11%               apache2             8422
0.10%               apache2             9372
0.10%               apache2             9241
0.10%               apache2             8424
0.09%               apache2             9429

If you want to see more details, the ps chisel provides a more verbose alternative:

sysdig -r monitoring-wordpress.scap -c ps container.name=wordpress-sysdig_wordpress_1

TID     PID     USER        VIRT       RES        FDLIMIT   CMD
5896    5896    root        232.82M    22.32M     429496729 apache2
8383    8383    www-data    307.44M    25.46M     429496729 apache2
8422    8422    www-data    235.44M    22.90M     429496729 apache2
8424    8424    www-data    307.44M    25.46M     429496729 apache2
8897    8897    www-data    235.44M    22.89M     429496729 apache2
9154    9154    www-data    235.44M    22.91M     429496729 apache2
9241    9241    www-data    307.44M    25.66M     429496729 apache2
9242    9242    www-data    307.44M    25.67M     429496729 apache2
9300    9300    www-data    235.44M    22.89M     429496729 apache2
9372    9372    www-data    235.44M    22.89M     429496729 apache2
9413    9413    www-data    233.44M    20.77M     429496729 apache2

Useful Tips

If you run Sysdig to capture events as in the above example (sysdig -w monitoring-wordpress.scap), the event file will grow continuously until it consumes all the available space. There are a few methods that can help prevent this from happening:

• Specify the number of events Sysdig should capture by passing it the -n flag. Once Sysdig captures the specified number of events, it'll automatically exit:

sysdig -n 5000 -w monitoring-wordpress.scap

• Use the -C flag to configure Sysdig so that it breaks the capture into smaller files of a specified size. The following example continuously saves events to files < 10MB:

sysdig -C 10 -w monitoring-wordpress.scap

This will create a bunch of files no larger than 10 MB:

ls -lh monitoring-wordpress*

-rw-r--r--. 1 root root 9.6M Jan  7 17:13 monitoring-wordpress.scap0
-rw-r--r--. 1 root root 9.6M Jan  7 17:14 monitoring-wordpress.scap1
-rw-r--r--. 1 root root 9.6M Jan  7 17:14 monitoring-wordpress.scap2
-rw-r--r--. 1 root root 9.6M Jan  7 17:14 monitoring-wordpress.scap3
-rw-r--r--. 1 root root 9.6M Jan  7 17:14 monitoring-wordpress.scap4
-rw-r--r--. 1 root root 9.6M Jan  7 17:14 monitoring-wordpress.scap5
-rw-r--r--. 1 root root 9.6M Jan  7 17:14 monitoring-wordpress.scap6
-rw-r--r--. 1 root root 9.6M Jan  7 17:14 monitoring-wordpress.scap7
-rw-r--r--. 1 root root 6.4M Jan  7 17:14 monitoring-wordpress.scap8

• Specify the maximum number of files Sysdig should keep with the -W flag. For example, you can combine the -C and -W flags like so:

sysdig -C 10 -W 4 -w monitoring-wordpress.scap

The above command will only keep the last four capture files:

ls -lh monitoring-wordpress*

-rw-r--r--. 1 root root 7.2M Jan  7 17:21 monitoring-wordpress.scap0
-rw-r--r--. 1 root root 9.6M Jan  7 17:21 monitoring-wordpress.scap1
-rw-r--r--. 1 root root 9.6M Jan  7 17:21 monitoring-wordpress.scap2
-rw-r--r--. 1 root root 9.6M Jan  7 17:21 monitoring-wordpress.scap3
root@cd06093b141b:/# sysdig -C 10 -W 4 -w monitoring-wordpress.scap

Real-Time Monitoring

With Sysdig, you can also analyze data real-time. At first glance, this can seem like a daunting task because, by default, all events are continuously printed out to the console. Fortunately, chisels are here to help.

Let's take an example.

Analyze Processes on a Per Container Basis

1.Run the following command to list your containers:

docker ps

CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                  NAMES
5b253e74e8e7        sysdig/sysdig       "/docker-entrypoint.…"   9 minutes ago       Up 9 minutes                               sysdig
06def7875617        wordpress:latest    "docker-entrypoint.s…"   3 hours ago         Up 3 hours          0.0.0.0:8000->80/tcp   wordpress-sysdig_wordpress_1
6bd8418eb03f        mysql:5.7           "docker-entrypoint.s…"   3 hours ago         Up 3 hours          3306/tcp, 33060/tcp    wordpress-sysdig_db_1

2.You can analyze the processes running in the WordPress container with:

sysdig -pc -c topprocs_cpu container.name=wordpress-sysdig_wordpress_1

3.Similarly, you can analyze the processes running in the MySQL container:

sysdig -pc -c topprocs_cpu container.name=wordpress-sysdig_db_1

Note that, not much different from this example, Sysdig can monitor network traffic, disk usage, and so on.

In this tutorial, you have gone over the fundamentals of using Sysdig to get a clear understanding of the activity generated by your containers. The examples in this blog post helped you get started and, in future tutorials, we'll show you how to use Csysdig and Sysdig Inspect.