[systemd-devel] How to speed up detection of emmc partition and mount the filesystem

[Jóhann B. Guðmundsson]

On 2/4/19 7:22 PM, Petr wrote:

> Hello,
>
> I have custom linux on embedded machine generated with Buildroot 
> using  emmc drive which contains  root filesystem on /dev/mmcblk0p2 
> and application data on  /dev/mmcblk0p4. The root fileystem is mounted 
> pretty quickly, but the application data are mounted about 1.7s after 
> systemd starts, the main reason is that the mmcbl0p4 is found by 
> systemd after 1.4s. As a workaround I created service that is executed 
> right after the local-fs-pre.target which execute "mount 
> /dev/mmcblk0p4 /app" and that works, but I would like to know if there 
> is correct way how to tell systemd that I want to mount the root fs 
> and application fs sooner than everything else (I believe that what I 
> want is to tell systemd to mount /dev/mmcblk0p4 without waiting for 
> udev to find /dev/mmcblk0p4 as new device and start auto mount). 


Hmm... your solution could be a simple type mount unit which is ordered 
before the local-fs-pre.target but maybe not.

+ there are two type of embedded paths in this world those that are 
super tiny resource constrained and those that are not.

Former you dont use systemd for but instead some linux micro platform 
usually tied to or associated with internet of terror devices ( IoT ) 
like Soletta project, the latter you do use systemd for but only after 
systemd has been put on a diet so you will need to provide proper 
context here as in what that custom embedded devices does or is trying 
to do and why you need to shave those 1.4s off, what's the problem you 
are trying to solve with it?

JBG



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