watchdog: file oberservation during mount at startu & more

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Hi,

i am currently looking for hints concerning the following topics:

1) Start datalogger application after boot:

The goal is to start the application after the file system is completely  
mounted.
Since the datalogger application has a ram disk as temorary storage the  
rd has to be mounted before the application is started.

Q: Where to place/start the datalogger application (without login,  
headless system)

2) The watchdog service observes a special file located on the ram disk.
I get a lot of log entries related to the unmounted ram disk.


Q: How can this behaviour be solved?

Thanks - Udo


Re: watchdog: file oberservation during mount at startu & more
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You made that sound just like a course work question.

Google on how to setup a service under systemd.

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Not a good enough description of the problem, but maybe start with
man fstab

--  
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Re: watchdog: file oberservation during mount at startu & more
Am 29.03.2018 um 00:33 schrieb Andrew Gabriel:
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Ok,

the refine the question:

Where can information about the complete boot process be found?

What i am searching for is the sequence of initialisation, staring of  
services and other things being performed before any login occurs and  
-finally- when a user islogging in.

I try to find out where and how to place my own basic services for  
background processing. Some of them rely on other prerequisites such as  
mounted ramdisks etc.

Which logs are written by whom at which part of the boot process is also  
very interesting.


Thanks - Udo


Re: watchdog: file oberservation during mount at startu & more
On Thu, 29 Mar 2018 12:57:12 +0200, Newdo wrote:

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Have you looked at the Debian Reference documentation,

http://www.debian.org/doc/manuals/debian-reference/

If you need to know about stuff that happens after the Linux kernel is  
booted and controlling the startup process, this would be as as good a  
starting point as any, especially when combined with the systemd  
documentation. About the best documentation set I've found is here:

https://www.freedesktop.org/wiki/Software/systemd/
    
The main problems with systemd are that Poettering and his crew seem  
unable to stop mucking around with it and are fairly careless about code  
quality, testing and documentation. However, that's old news which became  
obvious way back when they bollixed up Gnome 2 before getting bored and  
starting to work on Gnome 3 without tidying up unfinished business on  
Gnome 2.  

Much more recently they managed to stuff up the logging daemon, which is  
now, apparently, part of systemd. A version got put live on the Fedora  
distro that screwed up mail system logging levels for Postfix and spamd:  
24 hours after a reboot the log levels changed so that all message  
related mail info-level logging just stopped. Fortunately somebody kicked  
their goolies good and hard over that, because fixes appeared, but not in  
a very timely fashion.  

I don't like this approach: the best part of the UNIX philosophy is that  
each program should do one thing and do it well, which also makes  
maintenance easier. We already have one giant all seeing, all dancing  
monolithic mishmash, the kernel, and don't need another.


--  
Martin    | martin at
Gregorie  | gregorie dot org

Re: watchdog: file oberservation during mount at startu & more
Am 29.03.2018 um 00:33 schrieb Andrew Gabriel:
Quoted text here. Click to load it

Ok,

to refine the question:

Where can information about the complete boot process be found?

What i am searching for is the sequence of initialisation, staring of  
services and other things being performed before any login occurs and  
-finally- when a user islogging in.

I try to find out where and how to place my own basic services for  
background processing. Some of them rely on other prerequisites such as  
mounted ramdisks etc.

Which logs are written by whom at which part of the boot process is also  
very interesting.


Thanks - Udo


Re: watchdog: file oberservation during mount at startu & more
following:

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    Do you mean:  

        between application of power and the transfer of control to Linux
kernel

or

        between the start of the kernel and the production of a login
prompt on the system console

or
        between the start of the kernel and the production of a login
prompt on a graphical environment


    For the First, you may have to pay Broadcom -- as I recall, Broadcom
provides a black-box blob to the R-Pi foundation which is loaded by the
graphics processor, and which then sets up the hardware and loads the Linux
kernel image into RAM before allowing the ARM processor to start execution.
{Many other boards use a customized version of U-Boot which runs on the
main processor and gets loaded by code in a small ROM in place of the
initial load going to the graphics processor). Don't know if searching the
ARM site would reveal generic documentation for configuring a processor
boot system (remember: ARM sells processor /designs/, it is up to the chip
designer to wrap the processor core with peripherals to provide booting
capability).

    Second and Third: Study Linux kernel configuration, device tree
definitions, and whatever run-level control scheme is in use. Debian based
OS have transitioned from Sys-V INIT to systemd (sys-V made sense to me; I
glanced at some systemd stuff and was immediately lost -- it was as cryptic
as the device tree). The main difference between 2 & 3 is that 2 stops with
processes waiting for input on text consoles, while 3 has to load an
X-Window environment and start the desktop login process waiting (if it
isn't configured to automatically login as a default user).
  


--  
    Wulfraed                 Dennis Lee Bieber         AF6VN
     snipped-for-privacy@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

Re: watchdog: file oberservation during mount at startu & more
On Thu, 29 Mar 2018 12:57:45 +0200, Newdo wrote:

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As somebody mentioned in the grubby subthread below, have a look into  
/etc/rc.local

Check the meaning of '&' at the end of a command in some command shells.



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