live: initial rollback hook subsystem

Currently done for 40-autologin script only but might be
more widely useful: when describing an action to be done
while forming the LiveCD image, also prepare the one that
undoes the effect so that an installed LiveCD doesn't
(mis)behave as if it were young again.

NB: livecd-install provides 50-{gdm,kdm}-autologin-off.sh
hooks which can collide with ours, so let's override those
until things are sorted out properly at both sides.

PS: some half-year old nodm hacks are still in place for t6/branch
(and #27451 should be re-examined when dropping those).

features.in/live/live/image-scripts.d/40-autologin

@@ -15,6 +15,28 @@ add_nopasswdlogin_group()
 	gpasswd -a "$USER" nopasswdlogin
 }
 
+BAK=".save"
+backup() {
+	[ -f "$1" -a ! -f "$1$BAK" ] || return 1
+	cp -av "$1" "$1$BAK"
+}
+
+restore_later() {
+	[ -n "$1" ] || return 0
+
+	local prefix="/usr/lib/alterator/hooks/livecd-preinstall.d"
+	[ -d "$prefix" ] || mkdir -p "$prefix"
+
+	local hook="$prefix/51-disable-autologin-again.sh"
+	[ -s "$hook" ] || cat >> "$hook" <<- EOF
+	#!/bin/sh
+	. livecd-functions
+	EOF
+
+	echo mv -v "\$destdir$1$BAK" "\$destdir$1" >> "$hook"
+	chmod +x "$hook"
+}
+
 ## setup runlevel
 INITTAB=/etc/inittab
 if [ -f "$INITTAB" ]; then
@@ -23,39 +45,62 @@ if [ -f "$INITTAB" ]; then
 fi
 
 ## autologin^2
+AUTOLOGIN_CFG=/etc/sysconfig/autologin
 if [ -x /usr/sbin/autologin ]; then
-	cat << E_O_F >> /etc/sysconfig/autologin
-USER=$USER
-AUTOLOGIN=yes
-E_O_F
+	backup "$AUTOLOGIN_CFG"
+	cat >> "$AUTOLOGIN_CFG" <<- EOF
+	USER=$USER
+	AUTOLOGIN=yes
+	EOF
+	restore_later "$AUTOLOGIN_CFG"
 fi
 
 ## lightdm autologin
 LIGHTDM_CONF=/etc/lightdm/lightdm.conf
 if [ -f "$LIGHTDM_CONF" ]; then
+	backup "$LIGHTDM_CONF"
 	sed -i \
 		-e "s/^#\(autologin-user=\).*$/\1$USER/" \
 		-e "s/^#\(autologin-user-timeout=0\)/\1/" \
 		"$LIGHTDM_CONF"
+	backup "/etc/group"
 	add_nopasswdlogin_group lightdm ||:
+
+	restore_later "$LIGHTDM_CONF"
+	restore_later "/etc/group"
 fi
 
 ## gdm2 autologin
 GDM_CONF=/etc/X11/gdm/custom.conf
 if [ -f "$GDM_CONF" ]; then
+	backup "$GDM_CONF"
 	sed -i -e '/\[daemon\]/aAutomaticLoginEnable=true\nAutomaticLogin='$USER \
 		"$GDM_CONF"
+	backup "/etc/group"
 	add_nopasswdlogin_group gdm ||:
+
+	restore_later "$GDM_CONF"
+	restore_later "/etc/group"
 fi
 
 autologin_kdm() {
+	backup "$1"
 	sed -i \
 		-e '/AutoLoginEnable/ s,^.*$,AutoLoginEnable=true,' \
 		-e '/AutoLoginUser/ s,^.*$,AutoLoginUser='$USER',' \
 		"$1"
+	restore_later "$1"
 }
 
 ## kdm3 autologin
+# FIXME: tde packages have kdmrc in /usr via an absolute symlink :-(
+KDM_ETC=/etc/X11/kdm
+KDM_USR=/usr/share/kde/config/kdm
+if [ "$(readlink "$KDM_ETC")" = "$KDM_USR" ]; then
+	rm -f "$KDM_ETC"
+	ln -s ../.."$KDM_USR" "$KDM_ETC"
+fi
+
 KDMRC=/etc/X11/kdm/kdmrc
 if [ -f "$KDMRC" ]; then autologin_kdm "$KDMRC"; fi
 
@@ -67,22 +112,25 @@ if [ -f "$KDMRC" ]; then autologin_kdm "$KDMRC"; fi
 # FIXME nodm and xinitrc should be modified (also in p6)
 NODM_RC=/etc/sysconfig/nodm
 NODM_EXE=/usr/sbin/nodm
-
 if [ -x "$NODM_EXE" ]; then
-	cat << E_O_F >> "$NODM_RC"
-export NODM_USER=$USER
-E_O_F
+	backup "$NODM_RC"
+	cat >> "$NODM_RC" <<- EOF
+	export NODM_USER=$USER
+	EOF
+	restore_later "$NODM_RC"
 else
 	exit 0
 fi
 
-# FIXME: drop when #27449 is fixed
+# FIXME: drop since #27449 is fixed
 PREFDM=/etc/X11/prefdm
 if [ -f "$PREFDM" ] && ! grep -q nodm "$PREFDM"; then
+	backup "$PREFDM"
 	sed -i \
 		-e '/AUTOLOGIN_EXE=/ s,^.*$,AUTOLOGIN_EXE='$NODM_EXE',' \
 		-e '/AUTOLOGIN_CFG=/ s,^.*$,AUTOLOGIN_CFG='$NODM_RC',' \
 		"$PREFDM"
+	restore_later "$PREFDM"
 fi
 
 # FIXME: drop when #27451 is fixed