update install instructions

INSTALL

@@ -4,7 +4,8 @@ HOW TO CREATE A PAGESIGNER ORACLE INSTANCE.
 In N.Virginia region launch a t3a.micro instance and attach to it a volume created from
 snap-0c97f1c43c6bb2043 (used by Ubuntu 20.04 LTS ami-083654bd07b5da81d).
 
-Log into the instance and run: 
+Log into the instance and run:
+sudo apt update && sudo apt install liblz4-tool
 git clone --recurse-submodules https://github.com/tlsnotary/pagesigner-oracles
 cd pagesigner-oracles
 sudo ./make_oracle.sh

make_oracle.sh

@@ -15,6 +15,11 @@ if [ "$#" -eq 1 ]; then
     fi
 else
     count=$(blkid | grep $uuid | wc -l)
+    if [ $count == 0 ]; then
+        echo "a disk with uuid $uuid was not detected"
+        echo "please attach it first and rerun"
+        exit 1
+    fi
     if [ $count != 1 ]; then
         echo "more than one disk with uuid $uuid detected"
         echo "please specify explicitely what disk you'd like to modify, e.g:"
@@ -67,8 +72,8 @@ sed -i 's/- ssh//' $DISK/etc/cloud/cloud.cfg
 
 # unpack initrd, add our custom script and repack
 tmp=$(mktemp -d)
-dd if=/boot/initrd.img-5.11.0-1020-aws of=$tmp/microcode bs=512 count=9066
-dd if=/boot/initrd.img-5.11.0-1020-aws of=$tmp/initrd_old bs=512 skip=9066
+dd if=$DISK/boot/initrd.img-5.11.0-1020-aws of=$tmp/microcode bs=512 count=9066
+dd if=$DISK/boot/initrd.img-5.11.0-1020-aws of=$tmp/initrd_old bs=512 skip=9066
 mkdir $tmp/cpio && (unlz4 | cpio -i -D $tmp/cpio) < $tmp/initrd_old
 cp initrd/custom $tmp/cpio/scripts/init-premount/custom
 echo '/scripts/init-premount/custom "$@"' >> $tmp/cpio/scripts/init-premount/ORDER