1 files changed, 109 insertions, 0 deletions
diff --git a/nixos/modules/installer/tools/nixos-enter.sh b/nixos/modules/installer/tools/nixos-enter.sh
new file mode 100644
index 00000000000..89beeee7cf9
--- /dev/null
+++ b/nixos/modules/installer/tools/nixos-enter.sh
@@ -0,0 +1,109 @@
+#! @runtimeShell@
+# shellcheck shell=bash
+
+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" resolvConf="$1/etc/resolv.conf"
+
+    [[ -e /etc/resolv.conf ]] || return 0
+
+    # Handle resolv.conf as a symlink to somewhere else.
+    if [[ -L "$resolvConf" ]]; 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 of `../`s escaping the root.
+      resolvConf="$(readlink "$resolvConf")"
+      if [[ "$resolvConf" = /* ]]; then
+        resolvConf="$chrootDir$resolvConf"
+      else
+        resolvConf="$chrootDir/etc/$resolvConf"
+      fi
+    fi
+
+    # ensure file exists to bind mount over
+    if [[ ! -f "$resolvConf" ]]; then
+      install -Dm644 /dev/null "$resolvConf" || return 1
+    fi
+
+    mount --bind /etc/resolv.conf "$resolvConf"
+}
+
+chroot_add_resolv_conf "$mountPoint" || echo "$0: failed to set up resolv.conf" >&2
+
+(
+    # If silent, write both stdout and stderr of activation script to /dev/null
+    # otherwise, write both streams to stderr of this process
+    if [ "$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 "$mountPoint" systemd-tmpfiles --create --remove --exclude-prefix=/dev 1>&2 || true
+)
+
+unset TMPDIR
+
+exec chroot "$mountPoint" "${command[@]}"