Install Ssh Server on Embedded Device

Install ssh server on embedded device

You need to cross compile OpenSSH for your embedded device,Follow below steps

1. Download OpenSSH from
   http://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-6.6p1.tar.gz

2. extract it and cross-compile it using toolchain

   ./configure --host="board architecture"

   make

3. Copy sshd from compiled source and download it in your embedded
   device and run it

   /path/sshd

4. Try to connect with your embedded device

Adding ssh on embedded linux

Your device has an ARM processor. Your PC has an x86 processor. ARM and x86 are different processor architectures with different instruction sets. An executable program compiled for x86 consists of x86 instructions that an ARM processor cannot execute, and vice versa.

You need an ARM binary. Furthermore, you need an ARM binary that's compatible with the other software you have on your device. Specifically, you need either a statically linked binary (a binary that does not depend on anything else) or a binary linked with the right system libraries.

Check which standard library you have. If you have a file called /lib/ld-uClibc.so, you have uClibc, a small library intended for embedded systems. If you have a file called /lib/ld-linux.so.2, you have GNU libc, the same library that you have on your Ubuntu PC (and any other non-embedded Linux).

You have two choices of SSH clients and servers: OpenSSH and Dropbear. Dropbear is smaller, but has fewer features, in particular no SFTP.

If the standard library is Glibc, you can grab a binary from Debian's ARM distribution. Get the armel client or server package. Extract the .deb file by running

dpkg-deb -x openssh-….deb .

Then copy the binary from ./usr/bin or ./usr/sbin to the device.

If the standard library is uClibc, you'll need to grab a binary from a distribution based on uClibc. Dropbear is included in many embedded distribution. Openmoko, which shares some ancestry with Qtopia, includes Dropbear in its default installation. If you're going to want to install several programs, BuildRoot makes it very easy to obtain a cross-compiler and build common programs: you pretty much only need to follow the guide.

Manually get ssh access back on a embedded system (direct hdd access possible)

You can generate a new set of host keys on a handy Linux system as follows:

ssh-keygen -t rsa -b 2048 -f ssh_host_rsa_key
ssh-keygen -t dsa -b 1024 -f ssh_host_dsa_key

When ssh-keygen asks you for a passphrase, hit Enter without typing anything. Host keys must have an empty passphrase.

This creates the following files in your current directory:

ssh_host_rsa_key
ssh_host_rsa_key.pub
ssh_host_dsa_key
ssh_host_dsa_key.pub

You can then mount your device's hard drive and copy these four files into etc/ssh.

Note that when you try to ssh to the system afterwards, your ssh client will complain that the keys are different than expected, and probably refuse to connect. If you're running the OpenSSH client, you can correct this by using ssh-keygen again:

ssh-keygen -R <your_server_hostname>

How to install SSH host-key using Yocto

You can have a recipe that installs the key at the correct location. This key will be generated by you beforehand and "put" into an externalsrc recipe (inherit externalsrc and set EXTERNALSRC appropriately which can point to any path on the host system). The recipe lives in the version control environment you use but the key stays outside of it. Then you just add the resulting package to your image.

Remote connection to embedded device in field

I think that using OpenVPN would be a easy way to tunnel to the device. You can cross compile it and set it up as a client on the embedded device. Then you install it on your Linux box and set it up as a server.
Finally you install it on your work PC and set up as a client there.

It gives you a virtual network where all clients can talk to each other like they would be on a local network.

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