According to the Debian documentation[1] (Trisquel is indirectly derived from
it), using debootstrap may give different results than using the installer in
the resulting configuration. Using debootstrap also requires manual
configuration (Last time I used debootstrap, though, not for installing
Trisquel, I had to configure the timezone and /etc/fstab manually). I don't
recommend using debootstrap to install the system because of the above
reasons, instead use the netinstaller.
When a GNU/Linux system boots, it loads Linux and an “initrd” which is a
compressed cpio archive containing the first file hierarchy which is mounted
in RAM (Hence *init*ial *R*AM *d*isk). In an installed OS, the bootloader
boot this initrd system which in turn loads the main system[2], but the net
installer resides completely within this initrd. You can extract the Linux
image from “/casper/initrd.netinst” and initrd from
“/casper/vmlinuz.netinst” from the Trisquel 7.0 image[3], then boot it
with GRUB in the same way you boot your main system and use it to install
Trisquel. There are lots of examples about how to add an entry to GRUB which
you can consult for the details (Take note of whether you're using GRUB 1 or
GRUB 2 and look a corresponding tutorial)[4]. You can override the parition
where the kernel image and initrd are while installing. Bear in mind that
that you can left your computer in an unusable state if you interrupt the
installation after you have overridden the previous system but not yet
finished the new installation of Trisquel, so be careful. I recommend to
install only a basic CLI environment using the netinstaller, and then install
the other packages you want from it, using aptitude or apt-get, that way you
can control which packages get installed. If you want a graphic environment,
then you can first install the CLI environment, then get the desktop
environment and browser *without* the recommendations, then install the
recommendations and all the other packages you want. This way you can browse
the web while most packages are downloading.
The Debian documentation in [4] mentions a way to download the whole ISO
image to a partition and get the packages from there, rather than from the
network. I don't know how this can be done with Trisquel, but you can use the
procedure above. There are other ways to install Trisquel. For instance, you
can install it in a virtual machine and then adapt and copy the filesystem to
your real machine, but I haven't tested that at all; if you want to do it
that way, you will have to configure the bootloader manually and adapt
/etc/fstab to the setup of your new system.
I hope that it helps. Let us know if you need more help. Regards.
*DON'T FORGET TO MAKE BACKUPS PERIODICALLY AND BEFORE INSTALLING AN OS*
[1]: See <https://www.debian.org/releases/stable/amd64/apds03.html.en>.
[2]: See
<https://www.debian.org/doc/manuals/debian-reference/ch03.en.html#_an_overview_of_the_boot_strap_process>.
Remember that Trisquel is indirectly derived from Debian. The main difference
is that doesn't uses System V style init, but upstart because (I think) the
version on Ubuntu on which it's based uses upstart as well.
[3]: I partially tested the procedure using the aforesaid files from the CD
containing Trisquel with GNOME, because I had download it already, but I
think you can find the same files in the Netinstall CD.
[4]: Like
<https://www.debian.org/releases/stable/amd64/ch05s01.html.en#boot-initrd>.
You can also load a initrd and kernel image from a running system without
shutting down using kexec; but I suspect that there's a chance that there may
be problems since it doesn't initializes the hardware. I have used it with no
problems, but only in virtual machines.
