nixpkgs/nixos/modules/installer/tools/nixos-enter.sh

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#! @runtimeShell@
set -e
# Re-exec ourselves in a private mount namespace so that our bind
# mounts get cleaned up automatically.
if [ -z "$NIXOS_ENTER_REEXEC" ]; then
export NIXOS_ENTER_REEXEC=1
if [ "$(id -u)" != 0 ]; then
extraFlags="-r"
fi
exec unshare --fork --mount --uts --mount-proc --pid $extraFlags -- "$0" "$@"
else
mount --make-rprivate /
fi
mountPoint=/mnt
system=/nix/var/nix/profiles/system
command=("$system/sw/bin/bash" "--login")
silent=0
while [ "$#" -gt 0 ]; do
i="$1"; shift 1
case "$i" in
--root)
mountPoint="$1"; shift 1
;;
--system)
system="$1"; shift 1
;;
--help)
exec man nixos-enter
exit 1
;;
--command|-c)
command=("$system/sw/bin/bash" "-c" "$1")
shift 1
;;
--silent)
silent=1
;;
--)
command=("$@")
break
;;
*)
echo "$0: unknown option \`$i'"
exit 1
;;
esac
done
if [[ ! -e $mountPoint/etc/NIXOS ]]; then
echo "$0: '$mountPoint' is not a NixOS installation" >&2
exit 126
fi
mkdir -p "$mountPoint/dev" "$mountPoint/sys"
chmod 0755 "$mountPoint/dev" "$mountPoint/sys"
mount --rbind /dev "$mountPoint/dev"
mount --rbind /sys "$mountPoint/sys"
# modified from https://github.com/archlinux/arch-install-scripts/blob/bb04ab435a5a89cd5e5ee821783477bc80db797f/arch-chroot.in#L26-L52
chroot_add_resolv_conf() {
local chrootdir=$1 resolv_conf=$1/etc/resolv.conf
[[ -e /etc/resolv.conf ]] || return 0
# Handle resolv.conf as a symlink to somewhere else.
if [[ -L $chrootdir/etc/resolv.conf ]]; then
# readlink(1) should always give us *something* since we know at this point
# it's a symlink. For simplicity, ignore the case of nested symlinks.
# We also ignore the possibility if `../`s escaping the root.
resolv_conf=$(readlink "$chrootdir/etc/resolv.conf")
if [[ $resolv_conf = /* ]]; then
resolv_conf=$chrootdir$resolv_conf
else
resolv_conf=$chrootdir/etc/$resolv_conf
fi
fi
# ensure file exists to bind mount over
if [[ ! -f $resolv_conf ]]; then
install -Dm644 /dev/null "$resolv_conf" || return 1
fi
mount --bind /etc/resolv.conf "$resolv_conf"
}
chroot_add_resolv_conf "$mountPoint" || print "ERROR: failed to set up resolv.conf"
(
# If silent, write both stdout and stderr of activation script to /dev/null
# otherwise, write both streams to stderr of this process
if [ "$silent" -eq 1 ]; then
exec 2>/dev/null
fi
# Run the activation script. Set $LOCALE_ARCHIVE to supress some Perl locale warnings.
LOCALE_ARCHIVE="$system/sw/lib/locale/locale-archive" IN_NIXOS_ENTER=1 chroot "$mountPoint" "$system/activate" 1>&2 || true
# Create /tmp
chroot "$mountPoint" systemd-tmpfiles --create --remove --exclude-prefix=/dev 1>&2 || true
)
exec chroot "$mountPoint" "${command[@]}"