hpr-knowledge-base/hpr_transcripts/hpr1563.txt

Episode: 1563
Title: HPR1563: Starting Programs at boot on the Raspberry Pi
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr1563/hpr1563.mp3
Transcribed: 2025-10-18 05:08:08

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Hello and welcome Hacker Public Radio audience.
My name is Mr X and this is my 8th HBR podcast.
I've at the start by thanking the people at HBR for making this all possible.
It's really quite easy to send a show in, so why not give it a go?
If I can do it, I'm sure you can too.
I originally planned just to do one HBR episode a year.
It gives you all you to pull stuff together.
But I found I enjoyed it so much that I've done more than one this year.
Why don't you give it a go? I'm sure you'd enjoy it. It's really quite easy.
This podcast is kind of a bit off the cuff again.
Plan to describe how I start things at boot time on my Raspberry Pi.
It's the second to follow on from my previous podcast, which was running today
with you on the Raspberry Pi.
You can obviously modify this and use this to start anything on the Raspberry Pi.
There's probably a number of ways of doing this and that's what there's no errors in what
I'm about to tell you.
I chose to use the file xe rc.local to start stuff in.
If you look, if you go into, if you take an editor, your favourite editor,
whatever that is, and open up xe slash xe slash rc.local, it says,
if I read it out, it says rc.local.scrift is executed at the end of each
multi-session run level. Make sure that script will exit 0 on success or any other value on error.
In other words, enable or disable the script just change the execution bits.
Of course, that's the first thing when you first look at it, you'll find that
it's not executed by script, so whatever you do, it's going to do nothing.
We're going to do nothing for you.
So the first thing you've got to do is change the permission bits, so
issue the command, pseudo, space CH mod, space 755, space slash xe slash rc.local,
and that'll change the permissions on the file so that it's executable.
So, I run the standard Raspbian dissolution, it's running for a number of years now,
it's the first problem you have is that, did he wiki application as a dayman and runs,
and you wanted to run continuously all the time? So, if you were just to put,
I'll slash user slash spin slash did he wiki and put that into your script, it would never
complete, and therefore your pie wouldn't boot, so that's your first problem.
So, obviously, you could run it in the background, so you could put a nampr stand on the end,
and that puts it into the background, that's fine, you could do that.
But the problem with that is that when you do that, once that command is
fucked into the background, the next command is immediately run straight after that,
and if you've got two or three things set up on your in this file, then
it could put an awful lot of stress on your pie, because there's also some problems,
so you want things to run sequentially. So, you really want to introduce a delay between
each one starting, so it's a more controlled start up. So, in order to do that,
you put brackets around the command and separate them with a semi-colon, that way
you can start it with a line with the sleep command, then a semi-colon, and then the command you
want to run. So, being in mind that the sleep command will need to get bigger each time,
we'll need to take into account how long the previous command takes a settle down before you run
the next one. So, for example, to turn an example a bit, then trying to describe it in words,
I've actually got three things set up in this file, and so the first command I have
is sets the output of audio, it sets it to hard output to the jack plug on the pie,
because that's using the C-set command, MX or C-set command, because without that,
it can jump to the HDMI socket, and I found unplugging and plugging things,
whereas the pie was running, I think, locked it and caused problems. So, I wanted it to be
hard fixed to the audio socket, so that plugging and unplugging things didn't cause
a thing to freeze and lock up. So, how I did that as I used the command, open bracket, sleep space
one, semicolon, space, slash user, slash bin, slash A-mixer, space, C-set, space, num ID equals
three, space one, close bracket, space, ampersand. So, as I said, that, that waits one second and then
runs that command. So, the next command I ran was loading Diddy wiki, and this is the command that
I was really wanting to set up. So, the Diddy wiki command was, if you remember, it was Diddy wiki
space dash L, space one into dot 168 dot 1 dot 13, for example, space dash P, which is for port,
space 8000. So, that would mean it would be on listening on port 8000. That's fine,
but the thing is that this slash rc.local is run as a super user, is root. So, you definitely
don't want Diddy wiki running as a root, you just want it to be the run as a normal user.
And by default, the normal user on the Raspberry Pi is just Pi. So, you want to switch user to Pi
before you run Diddy wiki. So, the command for that should be, a complete command should be
open bracket, sleep space 3, semicolon, space su, space pi, space dash c, space inverted commas,
slash user, slash bin, slash Diddy wiki, space dash L, space one into dot 168 dot 1 dot 13, for example.
So, iPHS is going to be listening on, space dash P, that's for port, space 8000, inverted commas,
closed brackets, space ampersand, send it to the background. So, then that'll run after three
seconds. And then, i've got a third command, which actually runs a detached screen session,
that's very handy for attaching to. And to do that, I start with open brackets, sleep space
6, semicolon, space su, space pi, space dash c. So, again, that's switch user to Pi and on the
command, the command is space inverted commas, cd, space slash home slash pi, semicolon, space slash
user, slash bin slash screen, slash screen, I should say, space dash d dash m dash capital S.
I think that, I think from memory, that's the detached commas with M stands for or the S.
But it gives an example. Then, space pi dash debian. What was that for again? Cat member,
space dash c, space slash home slash pi slash dot screen rc dot multi run, and that's the
configuration file that sets up the multiple screens that you want to run it to when the screen
session starts, inverted commas, closed brackets, space, ampersand. So, there's the three commands
that run it, but I've got one that sets the, again, recapping it sets the audio output of the Pi
to the external 3.5 inch jack at boot time, that starts after one second, then in three seconds,
then immediately from three seconds, the diddywiki daemon runs, and then, again, starting from
that same start point, six seconds on the detached screen session starts. So, this is a
to recap. It's known that to one starts after one second, then after that one second,
it waits three seconds, then after that three seconds, it waits six seconds. What actually happens
is they all start running all at the same time, but because you've got a longer delay in each
they actually end up running in sequence. And of course, the last line of the script is exit space
zero, which means that the script exits with an exit code of zero, so there's no errors reported.
Okay, hope that wasn't all too painful to listen to, and you could follow along with it.
Obviously it's quite difficult to follow along in an audio with that, but what I'll do is,
I'll include my RC.local in the show notes so that you can follow along with it when you're
listening at your leisure. Alright, just one final thing before I go. I got some feedback from my
previous podcast on running ddywiki on the Raspberry Pi, and so I want to thank Tim, TTY for
that comment. I'm sorry, I didn't get charged to reply to that. Terrible, terrible. I kind of
forgot to check my comments, I must admit. So I'll read that that has commented out. It was
actually very interesting. It's just a quick note to say I enjoyed the episode, and I use and
but I use CI wiki, a fork of ddywiki. The main benefit of CI wiki is that you can choose to make
pages private and require a user to log in to view or edit the content. And it's given a link
HTTP source for us.net slash projects slash CI wiki. We did something simple at work to keep
sales quotes, but we are quite a small company, so a full CRM would be overkill. So I thought that
a wiki might be a good idea. I looked at loads, but decided that ddywiki, well CI wiki, was
simple enough that everyone could use it with around 10 minutes training, that was it, sorry,
with 10 minutes training. We have been running it for around three and a half years now, and a quick
alas.ddywiki shows that there are 1,137 pages in a ddywiki folder. I found that the build
in browser search control carrot space f works better when searching through page titles.
Also, backing it up is a piece of cake. I just have a script that runs at 4pm every day,
which gzips a whole ddywiki folder and emails it to me. The gziped archive is less than
2 megabytes in size, another one for being plain text. Anyway, thanks for the show. So that's great
Tim. Thanks for the great tip. I'll maybe have a look into that. I just want to turn on my
home server, so I'm not too worried about the security aspects, but that's very interesting.
I didn't know that. I'm sure somebody out there will find that useful as well. That's great.
So okay, I hope you all find this interesting and didn't worry all the hell.
I've got other ideas in the pipeline, so I'm not sure where I'll get a chance to get those out,
but if you want to contact me, I could be contacted at MrX at hpr.googlemail.com.
So that's MRX, AT, HPR, the at symbol, googlemail.com. So until next time, thank you and goodbye.
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