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Re: Is there a way to install Debian iso's from an existing installation onto a USB connected drive?




Quoting Brian (2019-05-02 16:01:31)
> On Thu 02 May 2019 at 15:12:46 +0200, Jonas Smedegaard wrote:
> 
> > Quoting Albretch Mueller (2019-05-02 14:42:08)
> > >  something like:
> > > 
> > >  1) download the iso's
> > > 
> > >  2) go: <some application> /dev/sdb
> > > 
> > >  where "/dev/sdb" is the device a USB disk is linked to
> > > 
> > >  then you would plug the disk on your computer and take it from 
> > >  there
> > > 
> > >  For that I used to burn live DVD but there should be a better way
> > 
> > Debian ISOs specifically are prepared to be used not only on optical 
> > drives but also booted from e.g. USB flash drives.
> > 
> > So "the better way" is to simply copy the image onto the device:
> > 
> >   sudo cp downloaded_image /dev/sdb
>  
> I use cat downloaded_image > /dev/sdb

Is there some benefit to that over cp?

Reason I prefer cp is that it is less confusing esp. for newcomers, in 
that it works also with sudo.



> > There is a cargo cult preaching the use of "dd" but that tool is 
> > like cutting trees with scissors: The wrong tool for the job!
> > 
> > There are some suggesting to avoid the need for sudo by messing with 
> > udev rules to grant non-root write access to removable devices.  
> > When properly established that is indeed more safe, but setting it 
> > up can go wrong in just as bad and more complex ways to decipher 
> > than simply mistyping the device name and wiping your main system 
> > drive.
> 
> This is along the same lines as Message #34 at
> 
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=751892
> 
>   > To random people reading this bug: please do not EVER do
>   > this or it may subtly break other things and then get you
>   > flamed when you will waste my time debugging that.
> 
> Although the issue is treated sympathetically towards the end of the 
> report, I don't believe I've ever seen an example of subtle breakage.
> 
> I agree with what is said in Message #23 at
> 
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=788662
> 
>   > In any case, it seems unfortunate that users can no
>   > longer write an image to a USB disk without using root.
>   > Especially because that makes it easier to make a mistake
>   > and overwrite the wrong disk. I've made ahabit of always
>   > dd'ing as non-root, to make it somewhat less likely that
>   > I'd overwrite a system disk.
> 
> Which is why I have a udev rule with
> 
>   SUBSYSTEM=="block", ATTRS{removable}=="1", GROUP="floppy"
> 
> in it. I might stop doing that if its use was demonstrated to have an
> adverse effect on other things I do.

Good for you that you have a hack that works.  Really!

Reason I discourage that approach more generally is not that I want to 
"flame" anyone (as in that bugreport you referenced aboe), but that I 
seek ways reasonable also for non-technical users: Your udev hack is 
more (not less) complicated for a non-technical user to do right 
compared to my one-liner sudo+cp command.  Your approach is sensible if 
doing _many_ such operations, but not when doing few, as a beginner.

At http://box.redpill.dk/ I currently use these initial steps:

[...]
 2) Connect microSD card to pc, and locate its device path:
    * On linux, try this command:
        lsblk --paths --nodeps
    * On macOS, try this command:
        ls /dev/rdisk?
    * Compare output of above command with and without card plugged in
      to not COMPLETELY OVERWRITE the wrong device below
 3) Make sure card is (connected but) not mounted:
    * On linux, check that lsblk lists no mountpoint entry
 4) Decompress and copy image onto card
    (adjust image name and device path as needed):
        gunzip core-lime2-1.0b22.img.gz
        sudo cp core-lime2-1.0b22.img PATH_TO_YOUR_SDCARD
[...]

That's not the method I use myself when testing those images over and 
over again, but the most sensible I have found so far for general use, 
also for those not fluent in shell pipes and udevadm queries and such...


 - Jonas

-- 
 * Jonas Smedegaard - idealist & Internet-arkitekt
 * Tlf.: +45 40843136  Website: http://dr.jones.dk/

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