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16 votes

Why is cron needed for Raspbian?

In Unix/Linux systems, lots of OS background tasks are run as cron jobs. To see what won't run if you stop the cron daemon, type these commands: ls -la /etc/cron.hourly ls -la /etc/cron.daily ls -...
Michael Harvey's user avatar
14 votes

Can I have 1 processor core just for my program?

Dedicating a core is probably overkill. I suggest you try my pigpio library. By default it will time GPIO level changes to within 10┬Ás. As a quick test I suggest you look at this Python example, ...
joan's user avatar
  • 71.1k
10 votes

Why is cron needed for Raspbian?

cron runs tasks (system or user chosen) which need to be run at regular intervals. By itself it uses negligible resources. I suggest you leave cron alone.
joan's user avatar
  • 71.1k
8 votes
Accepted

Can the Raspberry Pi 4 better distribute Python scripts to all four cores?

GIL is a design specification of the Python language, rather than a limitation of the Raspberry Pi [1] (multiprocessing is possible in Python, often with only a few lines of code [2], but ...
KPM's user avatar
  • 216
7 votes
Accepted

Can't delete pi user on Raspbian

I think I tracked it down for you... You removed the lightdm autologin for user pi ... but, if you are using noobs, there is another autologin here: /etc/systemd/system/[email protected] line 28: ...
RubberStamp's user avatar
  • 1,409
6 votes
Accepted

How many cores does the Pi 2 model B use by default?

This depends on the command (and note this applies to all multicore systems, not just the Pi 2). Not all tasks can be run in parallel. By analogy, consider a simple math problem 3 * 4 + 5 = None of ...
goldilocks's user avatar
  • 59.1k
5 votes

Can I have 1 processor core just for my program?

You can lock your program to one core using schedutils as described in this Cyberciti article: sudo apt-get install schedutils sudo taskset -c 3 -p 13545 # Lock PID 13545 to core 3 Other processes ...
Emil Vikström's user avatar
5 votes

Can't delete pi user on Raspbian

I did what rubberstamp did, but it still did noy work. So I went to preferences, raspberry pi configuration and removed the check from auto login. Then it worked for me.
Burd's user avatar
  • 51
5 votes

Why is cron needed for Raspbian?

Cron is actually very useful. Say you wanted to run a program once a day, then cron is your friend. You can schedule to run a program at any time during the day. I would definitely leave it on your ...
UNKNOWN's user avatar
  • 79
4 votes

Does there exist a list of all required processes, for a raspberry pi running raspbian, to continue proper operation?

A number of issues with killing random stuff that you don't know what it is... Each process running is doing something. If you kill it, whatever that something is won't be working anymore. So before ...
user10489's user avatar
  • 991
3 votes

How many cores does the Pi 2 model B use by default?

Separating a given task to be automatically processed by multiple CPUs, also called automatic parallelization, is generally a complex task. For some tasks (like compiling source-code) this is somewhat ...
MadMike's user avatar
  • 593
3 votes

Can I have 1 processor core just for my program?

Since you are having timing requirements Raspberry Pi is no longer the appropriate platform for this. It is not a real time platform and timing can be thrown off by a lot of different sources of ...
Maxthon Chan's user avatar
  • 1,051
2 votes

Can I have 1 processor core just for my program?

As per you requirement I don't think you need to use a single core processor. What you need is to make sure your program runs all the time. To achieve that, you can set the priority of your program ...
Vishwajeet Vishu's user avatar
2 votes

bash vs. & in startup, is there a difference?

tl;dr Preceding the file name with bash will cause it to be interpreted by bash. The & at the end will cause the program to be executed in the background. These "directives" are not mutually ...
techraf's user avatar
  • 4,329
2 votes

Kernels running SCHED_FIFO and SCHED_RR scheduling policies respectively for Raspberry Pi 3

A possible solution is outlined here: https://aelseb.wordpress.com/2016/01/06/change-linux-cpu-default-scheduler/ sched_fork: + /* Lorenzo Nava: force policy to RR */ + if (p->policy == ...
Bl00dh0und's user avatar
2 votes

nobody user running demon

nobody is a generic system user for unprivileged system processes. This is probably normal or a misconfiguration. I am suspicious that this demon supposed be run by root. Running samba root is ...
goldilocks's user avatar
  • 59.1k
2 votes

nobody user running demon

I have the same process. nobody 264 0.0 0.4 4304 2052 ? Ss 09:25 0:01 /usr/sbin/thd --triggers /etc/triggerhappy/triggers.d/ --socket /run/thd.socket --user nobody --deviceglob /dev/...
joan's user avatar
  • 71.1k
2 votes
Accepted

Plotting CPU and Ram utilization

egrep is just a shell script that runs grep -E. grep, egrep, and fgrep are a family of commands that share the same binary and man page. Your egrep is probably finding nothing because it is trying to ...
meuh's user avatar
  • 181
2 votes

Why is cron needed for Raspbian?

Cron is a lightweight process that doesn't use a lot of resources by itself. Plus many other things assume cron is there and working. Leave it there. Consider installing atop for diagnostics. When ...
Criggie's user avatar
  • 320
2 votes

Trying to kill all processes, but new processes keep spawning

Save yourself a lot of angst. There are a lot of similar posts, but no satisfactory solution. As you have discovered the name pi is used in lots of places. It is coded into many scripts. It is not ...
Milliways's user avatar
  • 60.3k
1 vote

How can I bring a proc started on a different shell in the background to my foreground and then put it back to background

The way I did something similar is to script starting the process within screen. screen can be attached and detached inside your ssh connection, to access the program running. SESSION_NAME=name NL=$(...
Douglas Leeder's user avatar
1 vote

Process in real time

You Need to exclude one CPU from the Overall scheduling in your /boot/cmdline.txt, afterwards you can assign the process to it via taskset as you already found out. To exclude a CPU, add the boot ...
Simon Banks's user avatar
1 vote

How to restart/release rfcomm for bluetooth communication?

rfcomm is one of the tools that has been deprecated by the BlueZ team as working at that low level can lead to unpleasant things happening on the system because those tools by passed the the bluetooth ...
ukBaz's user avatar
  • 1,457
1 vote

Can the Raspberry Pi 4 better distribute Python scripts to all four cores?

You can overcome the GIL limitation. The details are here and too long to copy into this post. The technology relies upon compiling some forms of Python code using the Just In Time compiler Numba. In ...
Nick's user avatar
  • 776
1 vote
Accepted

System Freezing Up, Bad SD?

The tests you have made are mainly made for rotating magnetic disk storages. The tests do not fit very well to solid-state storages like SD Cards. The hardware of them correct bad cells silently ...
Ingo's user avatar
  • 42.2k
1 vote

How to check for alive process in an infinite loop and use LED as status indicator?

If you do a ps -ef | grep blah_blah the result is: root 17625 17607 0 19:21 pts/0 00:00:00 grep blah_blah and therefore, the test will always be true. If you do: ps -ef | grep blah_bla[h] ...
Ljm Dullaart's user avatar
  • 2,521
1 vote
Accepted

Raspberry Pi 2 BCM2836 working but new Raspberry Pi 2 BCM2837 stuck on Rainbow Screen

Problem was with the Kernel, to repair this without updating packages you don't want to touch run. apt-get update apt-get install raspberrypi-bootloader This will update the bootloader package to ...
Sean Bulley's user avatar
1 vote

Raspberry Pi 2 BCM2836 working but new Raspberry Pi 2 BCM2837 stuck on Rainbow Screen

I have no idea how you might minimise the changes. I would use the following command to update the firmwaresudo rpi-update.
joan's user avatar
  • 71.1k
1 vote
Accepted

Is there any way to further increase the speed of clk in spi?

Try to use a lower Clock divider in this line: bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_32); For example use BCM2835_SPI_CLOCK_DIVIDER_2 for the fastest possible data rate.
Domme's user avatar
  • 375
1 vote

First and Last things it does

Probably the easiest approach is to use Device Tree gpio-poweroff to set the state of a pin. This is probably the earliest stage of the boot process which you can control. I have not actually done ...
Milliways's user avatar
  • 60.3k

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