#!/bin/sh
# B12 (board, LFS host side): RAM-only Alpine chroot at /tmp/alpine on its own tmpfs (size-capped; umount frees everything).
#   chroot-up.sh <alpine-b13.tar.gz | ->      (- = stream from stdin)
# Mounts (only what X/apk need): proc, sysfs (ro), /dev (bind), /dev/pts (bind). No eMMC partition is touched.
set -u; R=/tmp/alpine; SZ=${ALPINE_TMPFS_SIZE:-160m}; SRC=${1:-}
log() { echo "[$(cut -d' ' -f1 /proc/uptime)] $*"; }
mnt() { grep -q " $1 " /proc/mounts; }
[ -n "$SRC" ] || { echo "usage: $0 <tar.gz|->"; exit 2; }
mkdir -p $R
mnt $R || mount -t tmpfs -o size=$SZ,mode=0755 alpine $R || { echo "CHROOT-UP FAIL tmpfs"; exit 1; }
if [ ! -x $R/bin/busybox ]; then
	if [ "$SRC" = - ]; then tar xzf - -C $R; else tar xzf "$SRC" -C $R; fi || { echo "CHROOT-UP FAIL extract"; exit 1; }
fi
mnt $R/proc || mount -t proc proc $R/proc
mnt $R/sys  || { mount -o bind /sys $R/sys && mount -o remount,bind,ro $R/sys; }
mnt $R/dev  || mount -o bind /dev $R/dev
mnt $R/dev/pts || mount -o bind /dev/pts $R/dev/pts
# DNS for apk inside the chroot: bearer DNS from the modem controller (falls back to 77.88.8.8)
DNS=$(sed -n 's/^DNS=//p' /run/aurora-modem/ipcfg 2>/dev/null | tr ',' ' '); [ -n "$DNS" ] || DNS=77.88.8.8
: > $R/etc/resolv.conf; for d in $DNS; do echo "nameserver $d" >> $R/etc/resolv.conf; done
log "CHROOT-UP OK $(cat $R/etc/alpine-release) used=$(df -k $R | awk 'NR==2{print $3}')k mounts=$(grep -c " $R" /proc/mounts)"