On Tuesday, 29 August 2017 17:45:48 BST Stroller wrote:
> > On 29 Aug 2017, at 16:35, Alan McKinnon <alan.mckinnon@gmail.com> wrote:
> >> Is it udev that's responsible for populating the dev nodes?
> >> (is that the right terminology?)
> >> 
> >> How do I force it to reconstruct the partition table? Surely one should
> >> expect to be able to format or partition a removable drive and have the
> >> dev nodes created without the necessity of rebooting?> 
> > run partprobe and see if that makes a difference. It forces the kernel
> > to re-organize it's idea of what partitions are available.
> > 
> > I would have thought SD Cards were treated like regular hotpluggable
> > devices like USB storage, but maybe not. I'd be interested to see the
> > results of running partprobe.
> 
>    $ sudo partprobe -s
>    /dev/sda: gpt partitions 1 2 3 4 5
>    /dev/sdb: msdos partitions 1
>    $
> 
> The following is also dumped to /var/log/messages:
> 
>    Aug 29 17:31:13 alrai sudo[20565]: stroller : TTY=pts/1 ;
> PWD=/home/stroller ; USER=root ; COMMAND=/bin/bash -c partprobe Aug 29
> 17:31:13 alrai sudo[20565]: pam_unix(sudo:session): session opened for user
> root by (uid=0) Aug 29 17:31:13 alrai kernel:  sdb: sdb1
>    Aug 29 17:31:13 alrai kernel:  sdb: sdb1
>    Aug 29 17:31:13 alrai sudo[20565]: pam_unix(sudo:session): session closed
> for user root
> 
> However no new device nodes are added in /dev.
> 
> This is a headless system, mostly used as a file server. It doesn't run a
> desktop (although I've run X11 apps using xpra a few times in the past).
> I've never done anything to set up hotplugging.
> 
> Stroller.

This may have been mentioned already, but do you have sys-fs/udisks installed?

Check the output of udisksctl status/monitor/info and see what it reveals.  
Then check if you can mount the device with udiskctl.
-- 
Regards,
Mick