A script to remove rootfs verification and install an openssh server - needs to be run twice with two reboots.

etc-setup.sh

#!/usr/bin/env bash

###
APPLICATION="${0##*/}"
ARCHIVE=''
CURRENTROOT="$(rootdev -s)"
GO=''
HOM=$HOME
NUM='0'
REV=4 # Added check for root.*.tgz & ui.mini plus cleanup
SUDO=''
TMOUT='5'
ret=0

## Exits the script with exit code $1, spitting out message $@ to stderr
error() {
    local ecode="$1"
    shift
    echo "$*" 1>&2
    exit "$ecode"
}

####
#### If we're not running as root, restart as root.
if [ ${UID:-$(id -u)} -ne 0 ]; then
   echo "Must be superuser to run."
   echo "Use 'sudo' or become root first ..."
   exit 1
##  echo "...elevating $USER to superuser..."
##  echo
##  exec sudo /bin/sh -e "$0" "$@"
#### If we're not running as root, use sudo
#  echo "...elevating $USER to superuser via 'sudo'..."
#  echo
#  SUDO='sudo'
fi

###
### Check to see if rootfs is read-write
if ${SUDO} mount -i -o remount,rw / 2>/dev/null; then
  echo "Your rootfs (${CURRENTROOT}) is mounted read-write ..."
  echo "*** $(mount | grep ' / ') ***"; echo
else
# ## Check for bootcache fix ...
# ret=$(grep -iq bootcache /usr/share/vboot/bin/make_dev_ssd.sh; echo $?)
# if [ $ret -gt 0 ];
# then echo "$ret: No 'bootcache' fix appplied yet. :("
#      error 2 "Not safe to continue, exiting..."/
# else echo "$ret: The 'bootcache' fix has been appplied - yay. :)"
#      echo "You can now run 'rw-rootfs' safely."
# fi
  echo "Making your rootfs read-write ..."
  /usr/libexec/debugd/helpers/dev_features_rootfs_verification || echo "'rootfs' modification failed ..."
  echo "*** Rebooting in $TMOUT seconds to make changes effective ***" 1>&2
  read -t $TMOUT -p "... ENTER 'a' TO ABORT! " GO
  if [ -n "${GO}" ]; then error 0 "Okay, ABORTING ..."; fi
  reboot && exit 
  # echo -n "... Press Ctrl-C to ABORT ... " 1>&2
  # sleep 10 && $SUDO reboot && exit $ret
 
fi

### Remove search for both crouton & linux partitions
###
### Check for crouton functions file ( for mounting custom partitions )
#crouton_mount='/var/crouton'
#linux_mount='/var/linux'
#if [ -s /usr/local/bin/cros_funcs ]; then
#  . /usr/local/bin/cros_funcs
#  ## mount Linux partition if it exists
#  mountlinux $linux_mount && echo "...a LINUX partition is${PRIOR} mounted on '$MOUNTLINUX'."
## ${SUDO} mount -B  /var/linux/ /mnt/stateful_partition/crouton/shared/linux/
#  ## mount CROUTON partition if it exists
#  mountcrouton   $crouton_mount   && echo "...a CROUTON partition is${PRIOR} mounted on '$MOUNTCROUTON'."
#else
#  ROOTDEVICE="`rootdev -d -s`"
#  ## mount Linux partition if it exists
#  linuxpart="`${SUDO} cgpt find -n -l ROOT-C "$ROOTDEVICE"`"
#  if [ "`${SUDO} cgpt show -i "$linuxpart" -s "$ROOTDEVICE"`" -gt 1 ]; then
#     [ ! -d $linux_mount ] && ${SUDO} mkdir -p $linux_mount 2>/dev/null
#     [   -d $linux_mount ] && ${SUDO} mount ${ROOTDEVICE}/$linuxpart $linux_mount 2>/dev/null
#     [   -d ${linux_mount}/crouton ] && ${SUDO} mount -o bind ${linuxpart}/crouton $crouton_mount 2>/dev/null
#  fi
#  ## mount crouton partition if it exists
#  croutonpart="`${SUDO} cgpt find -n -l CROUTON "$ROOTDEVICE"`"
#  if [ "`${SUDO} cgpt show -i "$croutonpart" -s "$ROOTDEVICE"`" -gt 1 ]; then
#     [ ! -d $crouton_mount ] && ${SUDO} mkdir -p $crouton_mount 2>/dev/null
#     [   -d $crouton_mount ] && ${SUDO} mount ${ROOTDEVICE}/$croutonpart $crouton_mount 2>/dev/null
#  fi
#fi

# ###
# ### Make chronos/user HOME
# if [ $SUDO_USER=chronos ]; then
#   HOM="/home/chronos/user"
# fi
# 
###
### CHECKING FOR ARCHIVE FOLDER
ARCHIVE=/var/crouton/archive
if [ ! -d $ARCHIVE ]; then
  echo "Standard location of folder $ARCHIVE not found..."
  if [ -d ${HOM}/Downloads/archive ]; then
    echo -n "Found one... "
    ARCHIVE="${HOM}/Downloads/archive"
    echo "Using $ARCHIVE ..."
  elif [ -d /var/linux/archive ]; then
    echo -n "Found one... "
    ARCHIVE="/var/linux/archive"
    echo "Using $ARCHIVE ..."
  elif [ -r ./$APPLICATION ]; then
    echo -n "Found one... "
    ARCHIVE="`pwd`"
    echo "Using $ARCHIVE ..."
  else
    echo "Sorry, an archive folder could not be found..."
    echo "Aborting archive file installation..."
#   exit 1
  fi
else
  echo "Using $ARCHIVE ..."
  ###
  ### ROUTINE TO INSTALL CONF FILES IF NEEDED
  INIT=/etc/init
  OPENSSH=0
  cd $ARCHIVE
  echo "Checking upstart files in /etc/init."
  for CONF in *.conf
  do
    if [ ! -s ${INIT}/$CONF ]; then
      echo "file `cp -v $ARCHIVE/$CONF $INIT` installed..."
      NUM=$(($NUM+1))
    elif ! diff ${INIT}/$CONF ${ARCHIVE}/$CONF 2>/dev/null 1>&2; then
      echo "file `cp -v ${ARCHIVE}/$CONF $INIT` updated..."
      NUM=$(($NUM+1))
    else
      echo "file '${INIT}/$CONF' previously installed..."
    fi
  # if [ "$CONF" = "openssh-server.conf" ]; then
  #   OPENSSH=1
  # fi
  done
fi

# ###
# ### CHANGE chromeos-boot-alert script delay from 30 seconds to 3 seconds
# SBIN=/sbin
# if ! diff ${SBIN}/chromeos-boot-alert ${ARCHIVE}/chromeos-boot-alert 2>/dev/null 1>&2; then
#   echo "file `cp -v ${ARCHIVE}/chromeos-boot-alert $SBIN` updated..."
#   chmod +x ${SBIN}/chromeos-boot-alert 2>/dev/null
#   NUM=$(($NUM+1))
# else
#   echo "file '${SBIN}/chromeos-boot-alert' not present or previously installed..."
# fi

###
### Check for openssh server setup
#echo
#if ! /usr/libexec/debugd/helpers/dev_features_ssh --q ; then
#  ###
#  ### Setup openssh-server
#  echo "Setting up new openssh server ..."
#  /usr/libexec/debugd/helpers/dev_features_ssh
#  NUM=$(($NUM+1))
#  echo "'openssh' server will start in /etc/init ..."
#else
#  echo "An openssh server was previously setup ..."
#  ls -Ll /etc/init/openssh-server.conf
#fi

###
### Check for root files
echo
if [ -f /root/.bash_profile ]; then
  echo "root files are alread in place ..."
elif [ -f /usr/local/src/root.*.tgz ]; then
  echo "Found root files, installing..."
  cd /usr/local/src
  tar xvaf root.*.tgz -C /
  cd
  NUM=$(($NUM+1))
else
  echo "No root.tgz file found ..."
fi

###
### Check for ui.mini
echo
if grep -q minioverride.so /etc/init/ui.conf; then
  echo "ui.mini changes already applied ..."
elif [ -f /usr/local/src/ui.mini ]; then
  echo "Found ui.mini file, adding it to ui.conf next..."
# echo "Editing ui.conf next ..."
# cd /usr/local/src
# nvim +39 /etc/init/ui.conf
  sleep 3
  cd /etc/init
  sed -i '40i\\n# Add below to bypass sudo restriction for chronos\nenv LD_PRELOAD=/usr/local/src/minioverride.so' ui.conf
  cd
  NUM=$(($NUM+1))
else
  echo "No ui.mini file found ..."
fi

###
### Reboot if needed.
echo 
if [ $NUM -gt 0 ]; then
  echo "NOTE: Reboot for $NUM changes to be applied."
  echo "*** Rebooting in $TMOUT seconds to make changes effective ***" 1>&2
  read -t $TMOUT -p "... ENTER 'a' TO ABORT! " GO
  if [ -n "${GO}" ]; then error 0 "Okay, ABORTING ..."; fi
    reboot && exit $ret
else
  echo "### No changes needed/made."
fi

Revision 3: Minor changes.

Revision 4: Added check for root.*.tgz & ui.mini plus cleanup