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Example Boot

myLinux

Introduction

myLinux is a UNIX like OS for embedded systems based on Buildroot. It serves as a testing ground for various embedded networking hardware and open source software projects by the main author. E.g., the init system is Finit, not BusyBox init which is default in Buildroot.

myLinux can be used to verify software components in a emulated setup, using Qemu, before deploying to an embedded target, or as a reference to other embedded Linux systems. Therefore, all defconfigs are set up to include support for running under Qemu.

Building

Buildroot is almost stand-alone, but need a few locally installed tools to bootstrap itself. For details, see the excellent manual. Briefly, to build a myLinux image; select the target and then make:

make espressobin_defconfig
make

Online help is available:

make help

To see available defconfigs for supported targets, use:

make list-defconfigs

Note: build dependencies: sudo apt install make libssl-dev

Monitoring with SNMP

myLinux use mini-snmpd as its SNMP agent. It is very small and therefore also very limited in functionality, but it is enough to monitor myLinux by remote if needed.

initctl enable snmpd
initctl reload

To test it you need an SNMP client. The following command installs snmpset, snmpget, snmpwalk, base MIBs and all standard MIBs needed. You may also be interested in a more graphical alternative, snmpB

sudo apt-get install snmp libsnmp-base snmp-mibs-downloader

When done you should be able to do the following:

snmpwalk -v2c -c public 192.0.2.42

SNMPv2-MIB::sysDescr.0 = STRING: myLinux Linux Virtual Devboard
SNMPv2-MIB::sysObjectID.0 = OID: SNMPv2-SMI::enterprises
SNMPv2-MIB::sysUpTime.0 = Timeticks: (465) 0:00:04.65
SNMPv2-MIB::sysContact.0 = STRING: [email protected]
SNMPv2-MIB::sysName.0 = STRING: chaos
SNMPv2-MIB::sysLocation.0 = STRING: GitHub
IF-MIB::ifNumber.0 = INTEGER: 1
IF-MIB::ifIndex.1 = INTEGER: 1
IF-MIB::ifDescr.1 = STRING: eth0
IF-MIB::ifOperStatus.1 = INTEGER: up(1)
IF-MIB::ifInOctets.1 = Counter32: 5557
IF-MIB::ifInUcastPkts.1 = Counter32: 45
IF-MIB::ifInDiscards.1 = Counter32: 0
IF-MIB::ifInErrors.1 = Counter32: 0
IF-MIB::ifOutOctets.1 = Counter32: 2958
IF-MIB::ifOutUcastPkts.1 = Counter32: 19
IF-MIB::ifOutDiscards.1 = Counter32: 0
IF-MIB::ifOutErrors.1 = Counter32: 0
SNMPv2-SMI::mib-2.25.1.1.0 = Timeticks: (71983) 0:11:59.83

snmpget -c public -v 2c 192.0.2.42 system.sysUpTime.0

SNMPv2-MIB::sysUpTime.0 = Timeticks: (2344) 0:00:23.44

Note: Other SNMP agents are also available in Buildroot, but mini-snmpd is pre-selected for myLinux targets.

Dropbear SSH

The most common embedded SSH daemon in use on embedded Linux systems today is Dropbear by the incredibly humble Matt Johnston.

Dropbear is one of a few services enabled by default in myLinux, it allows root access, but we recommend disabling this and setting up a regular user account after install.

Using Telnet

The Busybox telnetd is available in myLinux, for security reasons it is disabled by default, so you have to enable it:

initctl enable telnetd
initctl reload

Bugs & Feature Requests

Feel free to report bugs and request features, or even submit your own pull requests using GitHub.

Try Before Flashing

One of the most tedious things as an embedded engineer is to watch the new firmware image update, only after five minutes to find the device no longer booting! One way to reduce turnaround times when working is to test and develop your image in Qemu.

myLinux has built-in support for calling make run after a successful build. This is just a wrapper for calling the qemu.sh script that has been generated in your output/images/ directory. It comes with a few environment variables control the behavior.

  • MY_HOST=/path/to/host/share: When this is set Qemu shares the full path argument as /host inside your target system.

Licensing & References

With the exceptions listed below, myLinux v2 is distributed under the same terms as Buildroot, the GNU GPL. myLinux is only the build system, or glue, that ties the various Open Source components together. Each project included comes with source code, and sometimes local patch files, all with their own license and restrictions.