MidgardOS Developer Documentation

A website documenting creating the build root for MidgardOS

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Section 4 - Entering the Chroot and More Temporary Tools

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Entering the Chroot

When entering the chroot environment, it is essential that all required virtual filesystems are mounted before entry, and that the entry script is run as the root user. To do so, create a shell script with the following contents:

#!/bin/bash

if [ "$(id -u)" -ne 0 ]; then
    echo "This script must be run as root. Exiting"
    exit 1
fi

BRFS=/MidgardOS
if ! mountpoint -q $BRFS/dev; then
    echo "$BRFS/dev is not mounted. Mounting the devtmpfs filesystem"
    mount -vt devtmpfs devtmpfs $BRFS/dev
fi
if ! mountpoint -q $BRFS/dev/pts; then
    echo "$BRFS/dev/pts is not mounted. Mounting devpts filesystem"
    mount -vt devpts devpts -o gid=5,mode=620 $BRFS/dev/pts
fi
if ! mountpoint -q $BRFS/proc; then
    echo "$BRFS/proc is not mounted. Mounting proc filesystem"
    mount -vt proc proc $BRFS/proc
fi
if ! mountpoint -q $BRFS/sys; then
    echo "$BRFS/sys is not mounted. Mounting sysfs filesystem"
    mount -vt sysfs sysfs $BRFS/sys
fi
if ! mountpoint -q $BRFS/run; then
    echo "$BRFS/run is not mounted. Mounting tmpfs filesystem"
    mount -vt tmpfs tmpfs $BRFS/run
fi
if [ -h $BRFS/dev/shm ] && ! mountpoint -q $BRFS/dev/shm; then
    echo "$BRFS/dev/shm is a symlink. Ensuring target directory exists"
    install -v -d -m 1777 ${BRFS}$(realpath /dev/shm)
elif ! mountpoint -q $BRFS/dev/shm; then
    echo "$BRFS/dev/shm is not mounted. Mounting tmpfs filesystem"
    mount -vt tmpfs -o mode=1777,nosuid,nodev,inode64 tmpfs $BRFS/dev/shm
fi

chroot "$BRFS" /usr/bin/env -i         \
    HOME=/root                         \
    TERM="$TERM"                       \
    PS1='(buildroot chroot) \u:\w\$ '  \
    PATH=/usr/bin:/usr/sbin            \
    MAKEFLAGS="-j$(nproc)"             \
    TESTSUITEFLAGS="-j$(nproc)"        \
    /bin/bash --login

Once this series of commands has been run, you should successfully be inside the chroot’d build environment. To know for sure, you should see the following in your terminal:

# ./enter_chroot.sh
(buildroot chroot) I have no name!:/#

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