Flash a SD card with an image

# gzip -cd /path/to/*.img.gz|dd of=/dev/sdX bs=64k

Given you run a Raspberry Pi with LibreElec and some HDDs connected to it, to deliver content for your TV, you may want to fill the HDD from whereever.
ssh as well as rsync are great tools for this.

SSH

First activate ssh in Kodi > Settings > LibreElec > Services > SSH > Enable SSH

Better disable password authentification and make it a habit to only use pubkey authentification.
After you placed your public key

ssh-copy-id -i ~/.ssh/id_t420s_2_pi.pub root@<IP of Pi>

you can deactivate password access. Toggle on Kodi > Settings > LibreElec > Services > SSH > Disable SSH Password
As you cannot create directories and transfer files to that new directory in one go, you may need three more steps.
Edit your ~/.ssh/config to match an entry for the pi. Then

ssh pi "mkdir /media/s/Foundation"
scp -v /path/to/Foundation/* pi:/media/s/Foundation/

Rsync

Rsync is not part of the vanilla Libbreelec. Install it: Kodi > Add-ons > Search
Search for rsync and install Network Tools.

Login via ssh, which rsync should give you

/storage/.kodi/addons/virtual.network-tools/bin/rsync

Now copy your content to your Pi:

rsync -e ssh --rsync-path=/storage/.kodi/addons/virtual.network-tools/bin/rsync -av Foundation pi:/media/s/

Consider setting an alias in your ~/.bashrc or ~/.zshrc:

alias rp='rsync -e ssh --rsync-path=/storage/.kodi/addons/virtual.network-tools/bin/rsync -av --info=progress2'

shortening the long expression to

rp Foundation pi:/media/s/

via