=== SL7 Boot: how to add single-user boot entries to initial grub2 menu ===
 . '''''as root user'''''
 . 1) make a dated copy of prior /boot/grub2/grub.cfg, i.e. '''cp /boot/grub2/grub.cfg /boot/grub2/grub.cfg.20170117'''
 . 2) make a dated copy of prior /etc/default/grub, i.e. '''cp /etc/default/grub /etc/default/grub.20170117'''
 . 3) '''vi /etc/default/grub''', set these variables:

||<-3> ↓ GRUB_DISABLE_RECOVERY=(true/false)                                                                        ||
||   ↓   ||<-2> ↓ GRUB_DISABLE_SUBMENU=(true/false)                                                                ||
|| true  || true  || as delivered in stock SL7 distro, no single user entries                                      ||
|| false || true  || boot main menu will have single-user entry for every kernel<<BR>>'''as modified 2017/04/09/'''||
|| false || false || boot submenu will have single-user entry for every kernel                                     ||

 . 4) run '''grub2-mkconfig -o /boot/grub2/grub.cfg'''
 . 5) reboot, new single-user entries will be labelled "recovery"