Installation-instructions.md

 # Install packages on debian host system
 ```bash
-apt install acl dnf rpm git systemd-container python3-venv
+apt install acl dnf rpm git systemd-container python3-venv rsync
 ```
 
 # Clone git and checkout config files
@@ -38,11 +38,21 @@ python3 -m pip install git+https://github.com/systemd/mkosi.git
 mkosi -i -t directory -o /var/lib/machines/xcache-$(date +%Y-%m-%d-%H%M)
 ```
 
+# Build image (manual `dnf --installroot`)
+```bash
+img_name=xcache-$(date +%Y-%m-%d-%H%M)
+dnf -y --installroot /var/lib/machines/$img_name --releasever=7 install system-release bash yum
+rsync -av /var/local/mkosi/mkosi.extra/ /var/lib/machines/$img_name
+cp /var/local/mkosi/mkosi.postinst /var/lib/machines/$img_name/
+systemd-nspawn -D /var/lib/machines/$img_name /bin/bash
+systemd-nspawn -D /var/lib/machines/$img_name bash /mkosi.postinst
+```
+
 # Create xrootd user in host system
 We will map the xrootd user id inside the container (typically 999) to one shifted by 65536 * 10 on the host system. This is an arbitrary choice and one should check this range of user ids is not used by anything else.
 ```bash
 # for some reason that command might add a carriage return (therefore the sed) ...
-XRD_UID_INSIDE=$(systemd-nspawn -D /var/lib/machines/<img-name> id -u xrootd | sed 's/\r//')
+XRD_UID_INSIDE=$(systemd-nspawn -D /var/lib/machines/$img_name id -u xrootd | sed 's/\r//')
 let "XRD_UID_HOST = $XRD_UID_INSIDE + 65536 * 10"
 useradd --no-create-home --system -u $XRD_UID_HOST xrootd
 ```
@@ -62,7 +72,7 @@ setfacl -m "u:xrootd:r" /etc/grid-security/hostkey.pem
 # Start and enable xcache service running in container
 The running image has to be linked to `/var/lib/machines/xcache` in order to pick up the configuration in `/etc/systemd/nspawn/xcache.nspawn`.
 ```
-ln -s /var/lib/machines/{<img-name>,xcache}
+ln -s /var/lib/machines/{$img_name,xcache}
 machinectl start xcache
 machinectl enable xcache
 ```
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