grep is a good tool that is common enough to be found in most docker containers that can be used to perform various types of generic health checks.

• grep

The following command will check whether port 5613 is open. Note that the following can only guarantee that a numeric port is open from the perspective of the TCP/IP stack, yet it does not perform any "HTTP request" such as the one performed using curl or wget. In that sense, this a weaker test that should only be used if some program-specific stronger test cannot be used that would also additionally attest to the proper functionality of the program.

grep -qi ":"`printf '%04x' 5613` /proc/*/net/tcp || exit 1

Due to recent kernels, processes, process numbers and their corresponding command line can be fished out of /proc, such that the following command, for example:

grep -qa elasticsearch /proc/[0-9]/cmdline || exit 1

will check whether there is a process running whose command line parameters contain the string elasticsearch.

This is also a very weak test and can only guarantee that whatever string is being searched for is also the name of a process or is contained within the command-line parameters but without being able to say much else.