tree-wide: various terminal related fixlets (#38544)

Fixes #38524.
Fixes #38527.
Fixes #38552.

test/units/TEST-72-SYSUPDATE.sh

@@ -54,15 +54,18 @@ at_exit() {
 trap at_exit EXIT
 
 update_checksums() {
-	(cd "$WORKDIR/source" && sha256sum uki* part* dir-*.tar.gz >SHA256SUMS)
+    (cd "$WORKDIR/source" && sha256sum uki* part* dir-*.tar.gz >SHA256SUMS)
 }
 
 new_version() {
     local sector_size="${1:?}"
     local version="${2:?}"
 
-    # Create a pair of random partition payloads, and compress one
-    dd if=/dev/urandom of="$WORKDIR/source/part1-$version.raw" bs="$sector_size" count=2048
+    # Create a pair of random partition payloads, and compress one.
+    # To make not the initial bytes of part1-xxx.raw accidentally match one of the compression header,
+    # let's make the first sector filled by zero.
+    dd if=/dev/zero of="$WORKDIR/source/part1-$version.raw" bs="$sector_size" count=1
+    dd if=/dev/urandom of="$WORKDIR/source/part1-$version.raw" bs="$sector_size" count=2047 conv=notrunc oflag=append
     dd if=/dev/urandom of="$WORKDIR/source/part2-$version.raw" bs="$sector_size" count=2048
     gzip -k -f "$WORKDIR/source/part2-$version.raw"
 
@@ -354,7 +357,7 @@ EOF
         updatectl check
         rm -r /run/sysupdate.test.d
     fi
-    
+
     # Create seventh version, and update through a file:// URL. This should be
     # almost as good as testing HTTP, but is simpler for us to set up. file:// is
     # abstracted in curl for us, and since our main goal is to test our own code