To [install](/doc/templates/#installing) a specific Debian TemplateVM that is not currently installed in your system, use the following command in dom0:
For routine daily TemplateVM updates within a given Debian release, see [Updating software in TemplateVMs](/doc/software-update-domu/#updating-software-in-templatevms).
- [Install a fresh template to replace the existing one.](#installing) **This option may be simpler for less experienced users.** After you install the new template, redo all desired template modifications and [switch everything that was set to the old template to the new template](/doc/templates/#switching). You may want to write down the modifications you make to your templates so that you remember what to redo on each fresh install. In the old Debian template, see `/var/log/dpkg.log` and `/var/log/apt/history.log` for logs of package manager actions.
- [Perform an in-place upgrade of an existing Debian template.](/doc/template/debian/upgrade/) This option will preserve any modifications you've made to the template, **but it may be more complicated for less experienced users.**
The Debian way (generally) is to start daemons if they are installed.
This means that if you install (say) ssh-server in a template, *all* the qubes that use that template will run a ssh server when they start. (They will, naturally, all have the same server key.) This may not be what you want.
So be very careful when installing software in Templates - if the daemon spawns outbound connections then there is a serious security risk.
In general, a reasonable approach would be, (using ssh as example):
