epkg installed by normal user

Will install packages to EPKG_STORE_DIR=$HOME/.epkg/store/ There are many ways to run them.

transparent container

Ideal:

mount --bind $HOME/.epkg/store/ /opt/epkg/store/

However only /opt exists, so have to do some tricks:

mkdir -p $HOME/.epkg/opt/epkg
# this will become dead link in bind mount
for i in /opt/*
do
    ln -s $i $HOME/.epkg/opt/$(basename $i)
done
ln -s $HOME/.epkg/store $HOME/.epkg/opt/epkg/store
mount --bind $HOME/.epkg/opt /opt

Another option is to create the whole root layout in $env/, where you can create any dirs for mount.

https://unix.stackexchange.com/questions/66084/simulate-chroot-with-unshare/303660#303660

unshare -r chroot <target_folder> <command_w_path>

However that will prevent apps from using user namespace:

https://unix.stackexchange.com/questions/442996/what-rule-prevents-entering-a-user-namespace-from-inside-a-chroot

replace store dir to symlink (prefer)

After package installation,

ln -s /tmp/epkg/store/$user

if size($HOME/.e) < size(/opt/epkg/store)
    linkfile=$HOME/.e
else
    linkfile=/tmp/epkg/xxxxx # should prevent /tmp auto-delete
fi
ln -s $HOME/.epkg/store $linkfile
sed -i "s /opt/epkg/store/ $linkfile/ " $HOME/.epkg/store/new/files

However that will break md5sum integrity, which can be eliminated if we remove the store path part from md5 computing (with a dedicated md5sum calculate tool).

replace store dir to final dir

It will take some chars from the $hashpartaway,tomakeroomforsaving‘$HOME/.epkg/store` sed -i "s /opt/epkg/store/ $HOME/.epkg/store " $HOME/.epkg/store/new/files

embed and expand ${EPKG_STORE}

• do not hardcode /opt/epkg/store in ELF apps/libs, use "${EPKG_STORE}" instead
• let the elf loader or ld-linux.so expand "${EPKG_STORE}", however it looks hard/complex
• ${EPKG_STORE} in non ELF/shell scripts can be hard to expand