diff --git a/README.md b/README.md
index 8d54f78..6c92fe4 100644
--- a/README.md
+++ b/README.md
@@ -101,7 +101,7 @@ Directory           | Files                  | Note
 ### Generate installer ISO
 
 ```shell
-export DISK_DEVS=sda,sdb     # System has /dev/sda and /dev/sdb
+export DISK_DEVS=sda,sdb     # Disks usable by the installer; ones not present on the machine are skipped
 export MAIN_DISK=sda         # Install OS to /dev/sda
 export PARTSIZE_DOCKER=8192  # 8G
 export PARTSIZE_LOG=2048     # 2G
diff --git a/ks.tpl.cfg b/ks.tpl.cfg
index ee5ef6e..48048d3 100644
--- a/ks.tpl.cfg
+++ b/ks.tpl.cfg
@@ -7,7 +7,8 @@ cmdline
 reboot
 # Run the Setup Agent on first boot
 firstboot --disable
-ignoredisk --only-use=@@DISK_DEVS@@
+# ignoredisk/clearpart with the disks existing on this machine, generated in %pre
+%include /tmp/ks.diskdevs.cfg
 # Keyboard layouts
 keyboard --vckeymap=us --xlayouts='jp'
 # System language
@@ -25,8 +26,6 @@ group --name=docker
 
 %include /tmp/ks.media.cfg
 
-# Partition clearing information
-clearpart --all --initlabel --drives=@@DISK_DEVS@@
 # Create partitions
 part /boot/efi --fstype="efi" --ondisk=@@MAIN_DISK@@ --size=200 --fsoptions="umask=0077,shortname=winnt"
 part / --fstype="ext4" --ondisk=@@MAIN_DISK@@ --size=2048 --mkfsoptions="-U 64eb4db5-3385-46a5-a3d5-c48197a53555"
@@ -59,6 +58,26 @@ else
   echo "url --url http://172.16.250.1/iso" > /tmp/ks.media.cfg
 fi
 
+# Pick only the disks that exist on this machine
+diskdevs=
+for dev in $(echo @@DISK_DEVS@@ | tr "," " ")
+do
+  if [ -b "/dev/${dev}" ]
+  then
+    diskdevs="${diskdevs:+${diskdevs},}${dev}"
+  else
+    echo "disk ${dev} not found, skipped"
+  fi
+done
+if [ -z "${diskdevs}" ]
+then
+  echo "no disks in DISK_DEVS (@@DISK_DEVS@@) found"
+fi
+cat > /tmp/ks.diskdevs.cfg <<EOF
+ignoredisk --only-use=${diskdevs}
+clearpart --all --initlabel --drives=${diskdevs}
+EOF
+
 @@KS.PRE.CFG@@
 %end