found it like this

build/root.sh

@@ -44,7 +44,7 @@ ln -s /hostroot/root /root/.home
 
 mkdir -p /home/user/.ssh
 cp /root/.ssh/authorized_keys /home/user/.ssh/authorized_keys
-echo chown -Rv $UID_TO_ADD:$GID_TO_ADD /home/user
-chown -Rv $UID_TO_ADD:$GID_TO_ADD /home/user
-
+chown -R $UID_TO_ADD:$GID_TO_ADD /home/user
 echo "$USERNAME_TO_ADD ALL=(ALL) NOPASSWD: ALL" > /etc/sudoers.d/user
+
+

build/user.sh

@@ -34,6 +34,7 @@ nix-env -i myPackages
 # oh-my-zsh
 curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh > /tmp/installomz.sh
 export ZSH="$HOME/.zsh"
+export KEEP_ZSHRC=yes
 zsh /tmp/installomz.sh && rm /tmp/installomz.sh