Default to super_chroot if not running as root and USER_NS is supported.

Author: JillTyrell

KEEP/config.stage0

@@ -22,12 +22,6 @@ export HOSTCC=gcc
 ## stage0 builds in less than 2minutes using -j9 on an AMD 8core
 export MAKE_THREADS=1
 
-# in case you have linux kernel 3.8+ with CONFIG_USER_NS enabled,
-# you can use super_chroot in place of chroot, so you don't need
-# root perms to build.
-# if SUPER is set, the enter-chroot script will use super_chroot.
-#export SUPER=1
-
 # SCP_MIRRORS is a newline-separated list where the default download template
 # tries to download source tarballs from if set (before doing regular download).
 # first %s passed is the tarball filename, second %s the local destination.

README.md

@@ -63,8 +63,6 @@ Set the `SABOTAGE_BUILDDIR`, `A`, and `MAKE_THREADS` variables.
 You may usually ignore the other values.
 Both the config file and the COOKBOOK cover the meaning of these variables.
 
-Enable `SUPER` to use the following `./enter-chroot` script without root.
-
 NOTE: It is possible to build an i386 Sabotage from within an existing 32-bit
 chroot on a 64-bit system.
 The `enter-chroot` script automatically handles this scenario.
@@ -80,10 +78,6 @@ ATTENTION: if you're using void or arch linux, building gcc630 in stage1 might
 fail due to a buggy ld. there's a workaround though:
 https://github.com/sabotage-linux/sabotage/issues/505
 
-Older pre-3.8 Linux systems will not support the rootless chroot approach used
-by `./enter-chroot`.
-Disable `SUPER` and run `./enter-chroot` as root if you encounter an issue.
-
 At this point, stage1 is complete and your Sabotage chroot is set up. There are
 two optional steps to consider at this time:
 

enter-chroot

@@ -26,19 +26,18 @@ case "$A" in i?86)
 esac
 fi
 
-if [ ! -z "$SUPER" ] ; then
+uid="$(id -u)"
+if [ -d /proc/self/ns ] && [ "$uid" != "0" ] ; then
 	CHROOT=./super_chroot
 	if [ ! -x "$CHROOT" ] ; then
 		if ! "$CC" "$K"/super_chroot.c -static -s -Os -o "$CHROOT" 2>/dev/null ; then
 			echo "error: failed to build super_chroot!"
 			echo "try: musl-gcc KEEP/super_chroot.c -o super_chroot"
-			echo "or: unset SUPER and re-run ./enter-chroot as root."
+			echo "or: re-run ./enter-chroot as root."
 			exit 1
 		fi
 	fi
 else
-
-	uid="$(id -u)"
 	if [ "$uid" != "0" ]; then
 	    printf -- "need to be root. please enter password.\n"
 	    su -c "$0"
@@ -93,7 +92,7 @@ tryumount() {
 	fi
 }
 
-if [ -z "$SUPER" ] && [ -d "$R"/dev/pts ] ; then
+if [ "$CHROOT" = "chroot" ] && [ -d "$R"/dev/pts ] ; then
 	tryumount "$R"/src/tarballs
 	tryumount "$R"/dev/pts
 	tryumount "$R"/dev/shm