add mksh support

dracut.spec

@@ -222,6 +222,9 @@ rm -fr -- $RPM_BUILD_ROOT/%{dracutlibdir}/modules.d/00bootchart
 # we do not support dash in the initramfs
 rm -fr -- $RPM_BUILD_ROOT/%{dracutlibdir}/modules.d/00dash
 
+# we do not support mksh in the initramfs
+rm -fr -- $RPM_BUILD_ROOT/%{dracutlibdir}/modules.d/00mksh
+
 # remove gentoo specific modules
 rm -fr -- $RPM_BUILD_ROOT/%{dracutlibdir}/modules.d/50gensplash
 

modules.d/00mksh/module-setup.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+# called by dracut
+check() {
+    require_binaries /bin/mksh
+}
+
+# called by dracut
+depends() {
+    return 0
+}
+
+# called by dracut
+install() {
+    # If another shell is already installed, do not use mksh
+    [[ -x $initdir/bin/sh ]] && return
+
+    # Prefer mksh as /bin/sh if it is available.
+    inst /bin/mksh && ln -sf mksh "${initdir}/bin/sh"
+}
+