Packages from Unstable
When you need a new package that is in unstable, you can follow this procedure.
enter /target chroot
The installer does the install the directory /target.
You can get there before you reboot or by using the rescue mode
download & install package
Finding the right URL of a package without apt is somewhat hard. Point a browser to https://deb.debian.org/debian/pool/main/ and dig deeper from there. You might end up with an URL like https://deb.debian.org/debian/pool/main/i/initramfs-tools/initramfs-tools_0.73_all.deb so do
wget https://deb.debian.org/debian/pool/main/i/initramfs-tools/initramfs-tools_0.73_all.deb
to get it in your directory. With
dpkg -i initramfs-tools_0.73_all.deb
will it be installed.
When more packages are needed, you have to install them the same way.
Note: this wiki page was written for 380648 Please keep updates generic for other 'packages from unstable'