grub2 changes at https://github.com/CSC-IT-Center-for-Science/ansible-role-serial-console/commit/fcc3be7dd32a6cea0822b89c9a488b27efcab2a3

grub2.cfg.patch

--- grub.cfg.org        2016-02-09 09:00:06.535863226 +0200
+++ grub.cfg    2016-02-09 09:08:11.716782060 +0200
@@ -57,7 +57,9 @@
   fi
 }
 
-terminal_output console
+serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1
+terminal_input console serial
+terminal_output console serial
 if [ x$feature_timeout_style = xy ] ; then
   set timeout_style=menu
   set timeout=5
@@ -75,7 +77,7 @@
 ### BEGIN /etc/grub.d/01_users ###
 if [ -f ${prefix}/user.cfg ]; then
   source ${prefix}/user.cfg
-  if [ -n ${GRUB2_PASSWORD} ]; then
+  if [ -n "${GRUB2_PASSWORD}" ]; then
     set superusers="root"
     export superusers
     password_pbkdf2 root ${GRUB2_PASSWORD}
@@ -84,7 +86,7 @@
 ### END /etc/grub.d/01_users ###
 
 ### BEGIN /etc/grub.d/10_linux ###
-menuentry 'CentOS Linux (3.10.0-327.4.5.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-327.el7.x86_64-advanced-5a6fc528-6b9a-4e3d-84b5-9a6179425a6f' {
+menuentry 'CentOS Linux (3.10.0-327.4.5.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-327.4.5.el7.x86_64-advanced-5a6fc528-6b9a-4e3d-84b5-9a6179425a6f' {
        load_video
        set gfxpayload=keep
        insmod gzio
@@ -96,7 +98,7 @@
        else
          search --no-floppy --fs-uuid --set=root 68cdb8dd-06f5-421a-a83a-11636b3c1ef4
        fi
-       linux16 /vmlinuz-3.10.0-327.4.5.el7.x86_64 root=/dev/mapper/centos_io2-root ro selinux=0 crashkernel=auto rd.lvm.lv=centos_io2/root rd.lvm.lv=centos_io2/swap rhgb quiet console=tty0 LANG=en_GB.UTF-8
+       linux16 /vmlinuz-3.10.0-327.4.5.el7.x86_64 root=/dev/mapper/centos_io2-root ro selinux=0 crashkernel=auto rd.lvm.lv=centos_io2/root rd.lvm.lv=centos_io2/swap rhgb quiet console=tty0 console=tty0 console=ttyS0,115200
        initrd16 /initramfs-3.10.0-327.4.5.el7.x86_64.img
 }
 menuentry 'CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-327.el7.x86_64-advanced-5a6fc528-6b9a-4e3d-84b5-9a6179425a6f' {
@@ -111,7 +113,7 @@
        else
          search --no-floppy --fs-uuid --set=root 68cdb8dd-06f5-421a-a83a-11636b3c1ef4
        fi
-       linux16 /vmlinuz-3.10.0-327.el7.x86_64 root=/dev/mapper/centos_io2-root ro selinux=0 crashkernel=auto rd.lvm.lv=centos_io2/root rd.lvm.lv=centos_io2/swap rhgb quiet console=tty0 LANG=en_GB.UTF-8
+       linux16 /vmlinuz-3.10.0-327.el7.x86_64 root=/dev/mapper/centos_io2-root ro selinux=0 crashkernel=auto rd.lvm.lv=centos_io2/root rd.lvm.lv=centos_io2/swap rhgb quiet console=tty0 console=tty0 console=ttyS0,115200
        initrd16 /initramfs-3.10.0-327.el7.x86_64.img
 }
 menuentry 'CentOS Linux (0-rescue-e05bd7e4c40449eea22e9952600bc69c) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-e05bd7e4c40449eea22e9952600bc69c-advanced-5a6fc528-6b9a-4e3d-84b5-9a6179425a6f' {
@@ -125,10 +127,10 @@
        else
          search --no-floppy --fs-uuid --set=root 68cdb8dd-06f5-421a-a83a-11636b3c1ef4
        fi
-       linux16 /vmlinuz-0-rescue-e05bd7e4c40449eea22e9952600bc69c root=/dev/mapper/centos_io2-root ro selinux=0 crashkernel=auto rd.lvm.lv=centos_io2/root rd.lvm.lv=centos_io2/swap rhgb quiet console=tty0
+       linux16 /vmlinuz-0-rescue-e05bd7e4c40449eea22e9952600bc69c root=/dev/mapper/centos_io2-root ro selinux=0 crashkernel=auto rd.lvm.lv=centos_io2/root rd.lvm.lv=centos_io2/swap rhgb quiet console=tty0 console=tty0 console=ttyS0,115200
        initrd16 /initramfs-0-rescue-e05bd7e4c40449eea22e9952600bc69c.img
 }
-
+if [ "x$default" = 'CentOS Linux (3.10.0-327.4.5.el7.x86_64) 7 (Core)' ]; then default='Advanced options for CentOS Linux>CentOS Linux (3.10.0-327.4.5.el7.x86_64) 7 (Core)'; fi;
 ### END /etc/grub.d/10_linux ###
 
 ### BEGIN /etc/grub.d/20_linux_xen ###
 
 
--- /etc/default/grub.bkp       2016-02-09 08:59:59.534849922 +0200
+++ /etc/default/grub   2016-02-09 09:08:09.049777025 +0200
@@ -5,3 +5,6 @@
 GRUB_TERMINAL_OUTPUT="console"
 GRUB_CMDLINE_LINUX="selinux=0 crashkernel=auto rd.lvm.lv=centos_io2/root rd.lvm.lv=centos_io2/swap rhgb quiet console=tty0"
 GRUB_DISABLE_RECOVERY="true"
+GRUB_TERMINAL="console serial"
+GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
+GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS0,115200"