diff --git a/sysa/after.kaem b/sysa/after.kaem
index 8d0c53a..c356bec 100755
--- a/sysa/after.kaem
+++ b/sysa/after.kaem
@@ -18,9 +18,10 @@ prefix=/usr
 bindir=${prefix}/bin
 libdir=${prefix}/lib
 incdir=${prefix}/include
+srcdir=${prefix}/src
 TMPDIR=/tmp # tmpdir is needed for patch to work
 
-mkdir -p ${prefix} ${bindir} ${libdir} ${incdir} ${TMPDIR}
+mkdir -p ${prefix} ${bindir} ${libdir} ${incdir} ${srcdir} ${TMPDIR}
 
 # Remove remaining dependencies on /bin (stage0-posix directory)
 cp /${ARCH_DIR}/bin/blood-elf ${bindir}/blood-elf
diff --git a/sysa/bash-2.05b/bash-2.05b.kaem b/sysa/bash-2.05b/bash-2.05b.kaem
index 33c4415..b883f9d 100755
--- a/sysa/bash-2.05b/bash-2.05b.kaem
+++ b/sysa/bash-2.05b/bash-2.05b.kaem
@@ -51,4 +51,11 @@ ln -s ${prefix}/bin/bash ${prefix}/bin/sh
 cd ../..
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/bash
+
+    install ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/bzip2-1.0.8/bzip2-1.0.8.kaem b/sysa/bzip2-1.0.8/bzip2-1.0.8.kaem
index 28fa0ef..ef295cc 100755
--- a/sysa/bzip2-1.0.8/bzip2-1.0.8.kaem
+++ b/sysa/bzip2-1.0.8/bzip2-1.0.8.kaem
@@ -35,4 +35,11 @@ bzip2 --help
 cd ../..
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/bzip2
+
+    cp ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/coreutils-5.0/coreutils-5.0.kaem b/sysa/coreutils-5.0/coreutils-5.0.kaem
index 8f1c449..3550c76 100755
--- a/sysa/coreutils-5.0/coreutils-5.0.kaem
+++ b/sysa/coreutils-5.0/coreutils-5.0.kaem
@@ -38,4 +38,64 @@ cd ../..
 rm -r src/
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/install \
+        /usr/bin/basename \
+        /usr/bin/cat \
+        /usr/bin/chmod \
+        /usr/bin/cksum \
+        /usr/bin/cp \
+        /usr/bin/csplit \
+        /usr/bin/cut \
+        /usr/bin/echo \
+        /usr/bin/expand \
+        /usr/bin/factor \
+        /usr/bin/false \
+        /usr/bin/fmt \
+        /usr/bin/fold \
+        /usr/bin/head \
+        /usr/bin/id \
+        /usr/bin/join \
+        /usr/bin/kill \
+        /usr/bin/link \
+        /usr/bin/ln \
+        /usr/bin/logname \
+        /usr/bin/mkfifo \
+        /usr/bin/mkdir \
+        /usr/bin/mknod \
+        /usr/bin/nl \
+        /usr/bin/od \
+        /usr/bin/paste \
+        /usr/bin/pathchk \
+        /usr/bin/printf \
+        /usr/bin/ptx \
+        /usr/bin/pwd \
+        /usr/bin/readlink \
+        /usr/bin/rmdir \
+        /usr/bin/seq \
+        /usr/bin/sleep \
+        /usr/bin/split \
+        /usr/bin/sum \
+        /usr/bin/tail \
+        /usr/bin/tee \
+        /usr/bin/tr \
+        /usr/bin/tsort \
+        /usr/bin/unexpand \
+        /usr/bin/unlink \
+        /usr/bin/wc \
+        /usr/bin/whoami \
+        /usr/bin/test \
+        /usr/bin/touch \
+        /usr/bin/true \
+        /usr/bin/yes \
+        /usr/bin/ls \
+        /usr/bin/md5sum \
+        /usr/bin/mv \
+        /usr/bin/rm \
+        /usr/bin/sha1sum
+
+    install ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/gzip-1.2.4/gzip-1.2.4.kaem b/sysa/gzip-1.2.4/gzip-1.2.4.kaem
index e73404d..adbb0ea 100755
--- a/sysa/gzip-1.2.4/gzip-1.2.4.kaem
+++ b/sysa/gzip-1.2.4/gzip-1.2.4.kaem
@@ -37,4 +37,11 @@ chmod 755 ${bindir}/gunzip
 cd ../..
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/gzip
+
+    cp ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/heirloom-devtools-070527/heirloom-devtools-070527.kaem b/sysa/heirloom-devtools-070527/heirloom-devtools-070527.kaem
index 665c66d..1c7848e 100755
--- a/sysa/heirloom-devtools-070527/heirloom-devtools-070527.kaem
+++ b/sysa/heirloom-devtools-070527/heirloom-devtools-070527.kaem
@@ -44,4 +44,15 @@ install -m 644 ncform ${lexdir}
 cd ../../..
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/yacc \
+        /usr/bin/lex \
+        /usr/lib/mes/libl.a \
+        /yaccpar \
+        /lex/ncform
+
+    install ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/make-3.80/make-3.80.kaem b/sysa/make-3.80/make-3.80.kaem
index 8936f77..157660d 100755
--- a/sysa/make-3.80/make-3.80.kaem
+++ b/sysa/make-3.80/make-3.80.kaem
@@ -55,4 +55,11 @@ make --version
 cd ../..
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/make
+
+    cp ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/mes-0.24/mes-0.24.kaem b/sysa/mes-0.24/mes-0.24.kaem
index d0e5792..56953ef 100755
--- a/sysa/mes-0.24/mes-0.24.kaem
+++ b/sysa/mes-0.24/mes-0.24.kaem
@@ -314,6 +314,27 @@ cp include/sys/ucontext.h ${incdir}/sys/ucontext.h
 cp include/sys/user.h ${incdir}/sys/user.h
 cp include/sys/wait.h ${incdir}/sys/wait.h
 
-# Checksums
 cd ../..
-sha256sum -c ${pkg}.checksums
+
+# Checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/mes \
+        /usr/bin/mes-m2 \
+        /usr/bin/mescc.scm \
+        /usr/lib/x86-mes/crt1.s \
+        /usr/lib/x86-mes/crt1.o \
+        /usr/lib/x86-mes/x86.M1 \
+        /usr/lib/x86-mes/libmescc.s \
+        /usr/lib/x86-mes/libc+tcc.s \
+        /usr/lib/x86-mes/libc.s \
+        /usr/lib/x86-mes/libmescc.a \
+        /usr/lib/x86-mes/libc+tcc.a \
+        /usr/lib/x86-mes/libc.a \
+        /usr/lib/linux/x86-mes/elf32-header.hex2 \
+        /usr/lib/linux/x86-mes/elf32-footer-single-main.hex2
+
+    cp ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/patch-2.5.9/patch-2.5.9.kaem b/sysa/patch-2.5.9/patch-2.5.9.kaem
index 4805c7c..4653dd7 100755
--- a/sysa/patch-2.5.9/patch-2.5.9.kaem
+++ b/sysa/patch-2.5.9/patch-2.5.9.kaem
@@ -34,4 +34,11 @@ chmod 755 ${prefix}/bin/patch
 cd ../..
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/patch
+
+    cp ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/run.sh b/sysa/run.sh
index 7b6a5ee..192ec61 100755
--- a/sysa/run.sh
+++ b/sysa/run.sh
@@ -16,19 +16,18 @@ export PREFIX="${prefix}"
 export SOURCES="${sysa}"
 export DISTFILES="${sysa}/distfiles"
 export DESTDIR=/tmp/destdir
-export REPO="${PREFIX}/src/repo"
+# shellcheck disable=SC2154
+export SRCDIR="${srcdir}"
 
 create_sysb() {
     # Copy everything in
     echo "Creating sysb rootfs"
     mkdir -p "/sysb${PREFIX}"
-    for d in bin include lib libexec share; do
+    for d in bin include lib libexec share src; do
         # Minimise RAM (storage) use - use hard links
         cp -rl "${PREFIX}/${d}" "/sysb${PREFIX}/${d}"
     done
-    mkdir /sysb/usr/src
-    cp "${SOURCES}/helpers.sh" "${SOURCES}/SHA256SUMS.pkgs" "${SOURCES}/bootstrap.cfg" /sysb/usr/src/
-    cp -rl "${REPO}" "/sysb/${REPO}"
+    cp "${SOURCES}/helpers.sh" "${SOURCES}/SHA256SUMS.pkgs" "${SOURCES}/bootstrap.cfg" "/sysb/${SRCDIR}"
     populate_device_nodes /sysb
     echo "Creating sysb initramfs"
     gen_initramfs_list.sh -o "${PREFIX}/boot/initramfs-sysb.cpio.gz" /sysb
@@ -101,7 +100,7 @@ echo "Thank you! All done."
 
 echo "ARCH=${ARCH}" >> "${SOURCES}/bootstrap.cfg"
 
-mkdir -p "${DESTDIR}" "${REPO}" /dev
+mkdir -p "${DESTDIR}" "${SRCDIR}/repo" /dev
 
 build flex-2.5.11
 
diff --git a/sysa/sed-4.0.9/sed-4.0.9.kaem b/sysa/sed-4.0.9/sed-4.0.9.kaem
index 8670bf9..4ba79d4 100755
--- a/sysa/sed-4.0.9/sed-4.0.9.kaem
+++ b/sysa/sed-4.0.9/sed-4.0.9.kaem
@@ -31,4 +31,11 @@ chmod 755 ${prefix}/bin/sed
 cd ../..
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/sed
+
+    cp ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/tar-1.12/tar-1.12.kaem b/sysa/tar-1.12/tar-1.12.kaem
index 10b5e5c..527b25d 100755
--- a/sysa/tar-1.12/tar-1.12.kaem
+++ b/sysa/tar-1.12/tar-1.12.kaem
@@ -34,4 +34,11 @@ chmod 755 ${prefix}/bin/tar
 cd ../..
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/tar
+
+    cp ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/tcc-0.9.26/tcc-0.9.26.kaem b/sysa/tcc-0.9.26/tcc-0.9.26.kaem
index 9a1ce03..d08de00 100755
--- a/sysa/tcc-0.9.26/tcc-0.9.26.kaem
+++ b/sysa/tcc-0.9.26/tcc-0.9.26.kaem
@@ -388,4 +388,23 @@ tcc -ar cr ${libdir}/libgetopt.a getopt.o
 cd ../..
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/mes-tcc \
+        /usr/bin/boot0-tcc \
+        /usr/bin/boot1-tcc \
+        /usr/bin/boot2-tcc \
+        /usr/bin/boot3-tcc \
+        /usr/bin/boot4-tcc \
+        /usr/bin/tcc \
+        /usr/lib/mes/libc.a \
+        /usr/lib/mes/libgetopt.a \
+        /usr/lib/mes/crt1.o \
+        /usr/lib/mes/crti.o \
+        /usr/lib/mes/crtn.o \
+        /usr/lib/mes/tcc/libtcc1.a
+
+    cp ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi
diff --git a/sysa/tcc-0.9.27/tcc-0.9.27.kaem b/sysa/tcc-0.9.27/tcc-0.9.27.kaem
index 181b3c6..7c5dcc4 100755
--- a/sysa/tcc-0.9.27/tcc-0.9.27.kaem
+++ b/sysa/tcc-0.9.27/tcc-0.9.27.kaem
@@ -47,4 +47,11 @@ tcc -version
 cd ../..
 
 # Checksums
-sha256sum -c ${pkg}.checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/tcc
+
+    cp ${pkg}.checksums ${srcdir}
+else
+    sha256sum -c ${pkg}.checksums
+fi