Comments on: Chapter 3: Exploring Embedded Linux Systems

By: Idan

Idan — Fri, 23 Mar 2018 12:30:42 +0000

What does these commands do?
root@debian:~# apt-get install build-essential module-assistant
root@debian:~# m-a prepare

By: fake name

fake name — Wed, 17 Jan 2018 19:41:34 +0000

I had the same issue. I entered the command on my ssh terminal and the connection closed. I had to unplug the power from the RPi and plug it back in in order to restart it, then it went back to the graphical target and I was able to ssh back into it.

Curious to see what might be the cause.

By: Erwin

Erwin — Fri, 11 Aug 2017 10:45:14 +0000

Current Raspbian has no .dtb files but .dtbo in the /root/overlays directory

By: M

Mon, 10 Jul 2017 21:04:50 +0000

Errata: top of page 78 stat example, You can update the access and modify times artificially using touch -a text.txt
Should be test.txt

By: Nishand D'silva

Nishand D'silva — Wed, 11 Jan 2017 09:54:36 +0000

Hi,

Is there any solution on “sudo systemctl isolate multi-user.target”? I tried connecting the raspberry pi to the TV, but see no display as well. I can see the LED light for the SD card activity blinking. But nothing on the TV screen and cannot connect through the network.

Thanks,

By: Nishand D'silva

Nishand D'silva — Tue, 10 Jan 2017 15:03:30 +0000

Hi,
When I typed this command in the terminal window “sudo systemctl isolate multi-user.target’, the terminal window freezes.

After that I can no longer ping the address, I get the message as “Host is Down”.

I tried ssh and it freezes again, and after a wait of 2 -3 mins I get a message saying “Operation timed out”. Tried powering on and off a few times but i can’t connect to the RPI3.

Could you please help?

Thanks

By: Alec B

Alec B — Fri, 06 Jan 2017 22:30:07 +0000

I’ve got the serial connection going with PuTTY because I wanted to see the console output while booting. I was disappointed to see very little output. Apparently this newer version Raspberrian I have has silenced much of the output due to community feedback. I read a bit and discovered that the output can be turned back on by editing the /boot/cmdline.txt file and removing the word “quiet” from the text. Once removed I get a very satisfying dump of boot data. Apparently the amount of data can be further adjusted by adding “loglevel=x” where x can be a number from 1 to 5 (I believe 5 is the top limit). Unfortunately I can’t find any useful documentation on loglevel.

By: admin

admin — Sun, 16 Oct 2016 12:35:12 +0000

Hi Mitchell, I have not idea what is going wrong. There seems to be a stray “/” at the end of the the URL (i.e., “exploringRPi.git/”) but that is likely not the issue. It looks like a firewall problem, but I can’t see why your firewall would allow traffic from the Debian VM and other RPis, but not that upgraded Pi board. You may need to update your SSL certificates. I think it is something like sudo update-ca-certificates on the RPi but I don’t remember the exact syntax. Please let me know if you solve this. Thanks, Derek.

By: Mitchell

Mitchell — Thu, 13 Oct 2016 14:22:39 +0000

Has something changed with how the Jessie distro for RPi deals with secure web access? Specifically, I can no longer clone to the Pi using git. When I try to clone the code for the book I get:

“fatal: unable to access ‘https://www.github.com/derekmolloy/exploringRPi.git/’: gnutls_handshake() failed: The TLS connection was non-properly terminated.”

The same error results when I try to clone from a repo on my own git account, and it is definitely something that changed recently, probably with an apt update or upgrade, to one of my RPi 3 boards. I have worked with this board and install for several weeks and performed clones, pushes and pulls without issue, until now. As a test, I also tried using IceWeasle through a VNC connection to the Pi. It connects fine to any non-secured (“http://…”) sites, but fails trying to connect with any “https://…” sites, such as google. The error returned is:

“Error performing TLS handshake: GnuTLS error.”

As another test I made sure secure web access worked from the Debian VM I am connecting to the Pi with and everything works fine, suggesting it is something that changed on the Pi. I have other Pi boards (B+, 2 and 3) that all work fine but I have not run apt upgrade recently on any of them.

Any idea what might be happening here and how I might fix it? I’ve searched around the web for the error but find mostly references to issues with emacs or Linux server installation issues that didn’t help.

Thanks,

Mitchell

By: admin

admin — Sun, 28 Aug 2016 23:07:34 +0000

Hi John,
That is strange. I just tried it there using SSH and it seems to be okay:

pi@raspberrypi:~ $ sudo systemctl get-default
graphical.target
pi@raspberrypi:~ $ sudo systemctl isolate multi-user.target
pi@raspberrypi:~ $ uname -a
Linux raspberrypi 4.1.19-v7+ #858 SMP Tue Mar 15 15:56:00 GMT 2016 armv7l GNU/Linux

pi@raspberrypi:~ $ sudo systemctl get-default

graphical.target

pi@raspberrypi:~ $ sudo systemctl isolate multi-user.target

pi@raspberrypi:~ $ uname -a

Linux raspberrypi 4.1.19-v7+ #858 SMP Tue Mar 15 15:56:00 GMT 2016 armv7l GNU/Linux

Please let me know if you worked out what is happening. Kind regards, Derek.