It is not always in /bin , but /usr/...
AC_SUBST(PLYMOUTH_LIBS)
AC_PATH_PROG([SYSTEMD_ASK_PASSWORD_AGENT], [systemd-tty-ask-password-agent])
+AC_PATH_PROG([UDEVADM], [udevadm])
AC_ARG_ENABLE(pango, AS_HELP_STRING([--enable-pango],[enable building with pango, disabled there is no encryption prompts]),enable_pango=$enableval,enable_pango=yes)
AM_CONDITIONAL(ENABLE_PANGO, [test "$enable_pango" = yes])
[Service]
ExecStart=@PLYMOUTH_DAEMON_DIR@/plymouthd --mode=boot --pid-file=@plymouthruntimedir@/pid --attach-to-session
-ExecStartPost=-/bin/udevadm settle --timeout=30 --exit-if-exists=/sys/class/drm/card0/dev ; /bin/udevadm settle --timeout=30 --exit-if-exists=/sys/class/graphics/fb0/dev ; @PLYMOUTH_CLIENT_DIR@/plymouth show-splash
+ExecStartPost=-@UDEVADM@ settle --timeout=30 --exit-if-exists=/sys/class/drm/card0/dev ; @UDEVADM@ settle --timeout=30 --exit-if-exists=/sys/class/graphics/fb0/dev ; @PLYMOUTH_CLIENT_DIR@/plymouth show-splash
Type=forking
KillMode=none
SendSIGKILL=no