// reference

Setup and write isolation

You mount a view of any original path. Reading files that are only at this path still works. But, creating new file/sub-directory places it in session layer only. Original path is not modified.

mkdir -p ~/pfs-base ~/pfs-session ~/pfs-mnt
echo hello > ~/pfs-base/hello.txt

export SESSION_LAYER_DIR=~/pfs-session
export BASE_LAYER_DIRS=~/pfs-base
prismafs ~/pfs-mnt

cat ~/pfs-mnt/hello.txt
echo world > ~/pfs-mnt/new.txt
ls ~/pfs-session

cat prints hello (from BASE layer). ls in SESSION shows only new.txt. Base layer is unchanged.

Leave it mounted for following b, c, and d cases.