I've just installed Debian Sid on my computer but I cannot mount external USB drives as you can see in the image.
Cannot mount "SENZATITOLO"
What should I do?
You are using a lightweight window manager. I've had this problem before in another such window manager. So it sounds like a problem with polkit to me. Does your system have a directory called
/etc/polkit-1/localauthority/? If so, create a file (as root)... I use the nano text editor here. Paste into the terminal with CTRL + SHIFT + V.
su root nano /etc/polkit-1/localauthority/50-local.d/55-storage.pkla
add the following lines:
[Storage Permissions] Identity=unix-group:plugdev Action=org.freedesktop.udisks.filesystem-mount;org.freedesktop.udisks.drive-eject;org.freedesktop.udisks.drive-detach;org.freedesktop.udisks.luks-unlock;org.freedesktop.udisks.inhibit-polling;org.freedesktop.udisks.drive-set-spindown ResultAny=yes ResultActive=yes ResultInactive=no
now add yourself to the plugdev group:
usermod -a -G plugdev <your username>
logout and log back in. If it is polkit, you should be able to mount media now.