docker-storage-setup.sh

#!/bin/bash

#--
# Copyright 2014 Red Hat, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#++

#  Purpose:  This script grows the root filesystem and sets up LVM volumes
#            for docker metadata and data.
#  Author:   Andy Grimm <agrimm@redhat.com>

set -e

# Read the config.  Currently supported options:
# DEVS: A quoted, space-separated list of devices to be used.  This currently
#       expects the devices to be unpartitioned drives.  If "VG" is not
#       specified, then use of the root disk's extra space is implied.
#
# VG:   The volume group to use for docker storage.  Defaults to the volume
#       group where the root filesystem resides.  If VG is specified and the
#       volume group does not exist, it will be created (which requires that
#       "DEVS" be nonempty, since we don't currently support putting a second
#       partition on the root disk).
#
# The options below should be specified as values acceptable to 'lvextend -L':
#
# ROOT_SIZE: The size to which the root filesystem should be grown.
#
# DATA_SIZE: The desired size for the docker data LV.  Defaults to using all
#            free space in the VG after the root LV and docker metadata LV
#            have been allocated/grown.
#
# Other possibilities: 
# * Support lvm raid setups for docker data?  This would not be very difficult
# if given multiple PVs and another variable; options could be just a simple
# "mirror" or "stripe", or something more detailed.
source /etc/sysconfig/docker-storage-setup

# Read mounts
ROOT_DEV=$( awk '$2 ~ /^\/$/ && $1 !~ /rootfs/ { print $1 }' /proc/mounts )
ROOT_VG=$( lvs --noheadings -o vg_name $ROOT_DEV )
ROOT_PVS=$( pvs --noheadings -o pv_name,vg_name | awk "\$2 ~ /^$ROOT_VG\$/ { print \$1 }" )

VG_EXISTS=
if [ -z "$VG" ]; then
  VG=$ROOT_VG
  VG_EXISTS=1
else
  for vg_name in $( vgs --noheadings -o vg_name ); do
    if [ "$vg_name" == "$VG" ]; then
      VG_EXISTS=1
      break
    fi
  done
fi

if [ -z "$DEVS" ] && [ -z "$VG_EXISTS" ]; then
  echo "Specified volume group $VG does not exists, and no devices were specified" >&2
  exit 1
fi

PVS=
GROWPART=

if [ -n "$DEVS" ] ; then
  for dev in $DEVS; do
    if expr match $dev ".*[0-9]"; then
      echo "Partition specification unsupported at this time." >&2
      exit 1
    fi
    # Use a single partition of a whole device
    # TODO:
    #   * Consider gpt, or unpartitioned volumes
    #   * Error handling when partition(s) already exist
    #   * Deal with loop/nbd device names. See growpart code
    PARTS=$( awk "\$4 ~ /"$( basename $dev )"[0-9]/ { print \$4 }" /proc/partitions )
    if [ -n "$PARTS" ]; then
      echo "$dev has partitions: $PARTS"
      exit 1
    fi
    size=$(( $( awk "\$4 ~ /"$( basename $dev )"/ { print \$3 }" /proc/partitions ) * 2 - 2048 ))
    cat <<EOF | sfdisk $dev
unit: sectors

${dev}1 : start=     2048, size=  ${size}, Id=8e
EOF
    pvcreate ${dev}1
    PVS="$PVS ${dev}1"
  done

  if [ -z "$VG_EXISTS" ]; then
    vgcreate $VG $PVS
  else
    # TODO:
    #   * Error handling when PV is already part of a VG
    vgextend $VG $PVS
  fi
  GROWPART=1
elif [ "$ROOT_VG" == "$VG" ]; then
  GROWPART=1
fi

# Note that growpart is only variable here because we may someday support
# using separate partitions on the same disk.  Today we fail early in that
# case.  Also note that the way we are doing this, it should support LVM
# RAID for the root device.  In the mirrored or striped case, we are growing
# partitions on all disks, so as long as they match, growing the LV should
# also work.
if [ -n "$GROWPART" ]; then
  for pv in $ROOT_PVS; do
    # Split device & partition.  Ick.
    echo growpart $( echo $pv | sed -r 's/([^0-9]*)([0-9]+)/\1 \2/' )
    echo pvresize $pv
  done
fi

# NB: We are growing root here first, because when root and docker share a
# disk, we'll default to giving docker "everything else."  This will be a
# problem if someone tries to assign root a value like"100%FREE".

if [ -n "$ROOT_SIZE" ]; then
  # TODO: Error checking if specified size is <= current size
  lvextend -L $ROOT_SIZE $ROOT_DEV || true
fi

# Reserve 0.1% of the free space in the VG for docker metadata.
# Calculating the based on actual data size might be better, but is
# more difficult do to the range of possible inputs.
VG_FREE_EXTS=$( vgs --noheadings --nosuffix --units s -o vg_free $VG )
META_SIZE=$(( $VG_FREE_EXTS / 1000 + 1 ))
lvcreate -l ${META_SIZE}S -n docker-meta $VG
if [ -n "$DATA_SIZE" ]; then
  # TODO: Error handling when DATA_SIZE > available space.
  lvcreate -L $DATA_SIZE -n docker-data $VG
else
  lvcreate -l "100%FREE" -n docker-data $VG
fi