Add the default user to some groups (audio, video).

src/scripts/customize_rootfs.sh

 #!/bin/bash
 
 # Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Script to customize the root file system after packages have been installed.
 #
 # NOTE: This script should be called by build_image.sh. Do not run this
 # on your own unless you know what you are doing.
@@ skipping 42 matching lines @@
   CRYPTED_PASSWD=$(cat $CRYPTED_PASSWD_FILE)
 else
   # Use a random password.  unix_md5_crypt will generate a random salt.
   echo "Using random password."
   PASSWORD="$(base64 /dev/urandom | head -1)"
   CRYPTED_PASSWD="$(echo "$PASSWORD" | openssl passwd -1 -stdin)"
   PASSWORD="gone now"
 fi
 
 # Set up a default user and add to sudo and the required groups.
-USERNAME="chronos"
+ADD_USER="chronos"
+ADD_GROUPS="audio video"
 SHELL="/bin/sh"
 if [[ -x "${ROOT_FS_DIR}/bin/bash" ]] ; then
   SHELL="/bin/bash"
 fi
-echo "${USERNAME}:x:1000:1000:${FULLNAME}:/home/${USERNAME}/:${SHELL}" | \
+echo "${ADD_USER}:x:1000:1000:${FULLNAME}:/home/${ADD_USER}/:${SHELL}" | \
   sudo dd of="${ROOT_FS_DIR}/etc/passwd" conv=notrunc oflag=append
-echo "${USERNAME}:${CRYPTED_PASSWD}:14500:0:99999::::" | \
+echo "${ADD_USER}:${CRYPTED_PASSWD}:14500:0:99999::::" | \
   sudo dd of="${ROOT_FS_DIR}/etc/shadow" conv=notrunc oflag=append
-echo "${USERNAME}:x:1000:" | \
+echo "${ADD_USER}:x:1000:" | \
   sudo dd of="${ROOT_FS_DIR}/etc/group" conv=notrunc oflag=append
-# TODO: Add USERNAME to adm,dialout,cdrom,floppy,audio,dip,video groups?
-sudo mkdir -p "${ROOT_FS_DIR}/home/${USERNAME}"
-sudo chown 1000.1000 "${ROOT_FS_DIR}/home/${USERNAME}"
+for i in $ADD_GROUPS; do
+  sudo sed -i "s/^\($i:x:[0-9]*:.*\)/\1,${ADD_USER}/g" \
+    "${ROOT_FS_DIR}"/etc/group
+done
+
+sudo mkdir -p "${ROOT_FS_DIR}/home/${ADD_USER}"
+sudo chown 1000.1000 "${ROOT_FS_DIR}/home/${ADD_USER}"
 cat <<EOF | sudo dd of="${ROOT_FS_DIR}/etc/sudoers" conv=notrunc oflag=append
 %adm ALL=(ALL) ALL
-$USERNAME ALL=(ALL) ALL
+$ADD_USER ALL=(ALL) ALL
 EOF
 sudo chmod 0440 "${ROOT_FS_DIR}/etc/sudoers"
 
 # Set CHROMEOS_VERSION_DESCRIPTION here (uses vars set in chromeos_version.sh)
 # Was removed from chromeos_version.sh which can also be run outside of chroot
 # where CHROMEOS_REVISION is set
 # We have to set (in build_image.sh) and use REAL_USER due to many nested
 # chroots which lose $USER state.
 . "${SCRIPTS_DIR}/chromeos_version.sh"
 if [ ${CHROMEOS_OFFICIAL:-0} = 1 ]; then
@@ skipping 151 matching lines @@
 cat <<EOF | sudo dd of="${ROOT_FS_DIR}/etc/network/interfaces"
 auto lo
 iface lo inet loopback
 EOF
 
 cat <<EOF | sudo dd of="${ROOT_FS_DIR}/etc/resolv.conf"
 # Use the connman dns proxy.
 nameserver 127.0.0.1
 EOF
 sudo chmod a-wx "${ROOT_FS_DIR}/etc/resolv.conf"