Without going into particulars, it suffices to say that Ubuntu 12.04 has the following script that sets up encrypted swap:
ecryptfs-setup-swap
The normal output of this script:
WARNING: An encrypted swap is required to help ensure that encrypted files are not leaked to disk in an unencrypted format. HOWEVER, THE SWAP ENCRYPTION CONFIGURATION PRODUCED BY THIS PROGRAM WILL BREAK HIBERNATE/RESUME ON THIS SYSTEM! NOTE: Your suspend/resume capabilities will not be affected. Do you want to proceed with encrypting your swap? [y/N]: y INFO: Setting up swap: [/dev/sda5] WARNING: Commented out your unencrypted swap from /etc/fstab * Stopping remaining crypto disks... * cryptswap1 (stopped)... [ OK ] * Starting remaining crypto disks... * cryptswap1 (starting).. * cryptswap1 (started)... [ OK ] INFO: Successfully setup encrypted swap!
To ensure that swap is working properly we can do the following:
fdisk -l
It should show something like /dev/mapper/cryptswap1:
Disk /dev/sda: 21.5 GB, 21474836480 bytes 255 heads, 63 sectors/track, 2610 cylinders, total 41943040 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00041a2a Device Boot Start End Blocks Id System /dev/sda1 * 2048 40105983 20051968 83 Linux /dev/sda2 40108030 41940991 916481 5 Extended /dev/sda5 40108032 41940991 916480 82 Linux swap / Solaris Disk /dev/mapper/cryptswap1: 938 MB, 938475520 bytes 255 heads, 63 sectors/track, 114 cylinders, total 1832960 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x6943c31d Disk /dev/mapper/cryptswap1 doesn't contain a valid partition table
Then we can check that changes are automatically applied to /etc/fstab configurations file. It also should contain this /dev/mapper/cryptswap1:
# /etc/fstab: static file system information. # # Use 'blkid -o value -s UUID' to print the universally unique identifier # for a device; this may be used with UUID= as a more robust way to name # devices that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 # / was on /dev/sda1 during installation UUID=fcc47f97-2a8a-45e6-a389-15cff216f652 / ext4 errors=remount-ro 0 1 # swap was on /dev/sda5 during installation #UUID=4a885082-3ce6-4725-b536-97706162f6b9 none swap sw 0 0 /dev/fd0 /media/floppy0 auto rw,user,noauto,exec,utf8 0 0 /dev/mapper/cryptswap1 none swap sw 0 0
and unencrypted swap should be commented out.
The same situation with /etc/crypttab:
# <target name> <source device> <key file> <options> cryptswap1 /dev/sda5 /dev/urandom swap,cipher=aes-cbc-essiv:sha256
And finally
free -m
should show corresponding swap size:
total used free shared buffers cached Mem: 495 320 175 0 125 111 -/+ buffers/cache: 82 413 Swap: 894 0 894
below I provided the source code of /usr/bin/ecryptfs-setup-swap script:
#!/bin/sh -e
# ecryptfs-setup-swap
# Copyright (C) 2008 Canonical Ltd.
#
# Authors: Dustin Kirkland <kirkland@ubuntu.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# The cryptswap setup used here follows a guide published at:
# * http://ubuntumagnet.com/2007/11/creating-encrypted-swap-file-ubuntu-using-cryptsetup
TEXTDOMAIN="ecryptfs-utils"
error() {
echo `gettext "ERROR:"` "$@" 1>&2
exit 1
}
info() {
echo `gettext "INFO:"` "$@"
}
warn() {
echo `gettext "WARNING:"` "$@" 1>&2
}
usage() {
echo
echo `gettext "Usage:"`
echo " $0 [-f|--force] [-n|--no-reload]"
echo
exit 1
}
# Handle command line options
FORCE=0
while [ ! -z "$1" ]; do
case "$1" in
-f|--force)
FORCE=1
shift 1
;;
-n|--no-reload)
NO_RELOAD=1
shift 1
;;
*)
usage
;;
esac
done
# Ensure that cryptsetup is available
[ -x /sbin/cryptsetup ] || error `gettext "Please install"` "'cryptsetup'"
# Ensure that we're running with root privileges
[ -w /etc/passwd ] || error `gettext "This program must be run with 'sudo', or as root"`
# Count swap spaces available
if [ $(grep -c "^/" /proc/swaps) -eq 0 ]; then
mem=$(grep "^MemTotal:" /proc/meminfo | awk '{print $2}')
swapsize=$((4*$mem))
info "You do not currently have any swap space defined."
echo
echo `gettext "You can create a swap file by doing:"`
echo " $ sudo dd if=/dev/zero of=/swapfile count=$swapsize"
echo " $ sudo mkswap /swapfile"
echo " $ sudo swapon /swapfile"
echo
echo `gettext "And then re-run"` "$0"
echo
exit 0
fi
swaps=$(grep "^/" /proc/swaps | awk '{print $1}')
filtered_swaps=$(
for swap in $swaps; do
# Make sure this is swap space
if [ "$(blkid -o value -s TYPE $swap)" != "swap" ]; then
warn "[$swap]" `gettext "does not appear to be swap space, skipping."`
continue
fi
if [ "${swap#/dev/ram}" != "$swap" ] || [ "${swap#/dev/zram}" != "$swap" ]; then
warn "[$swap]" `gettext "is a RAM device, skipping."`
continue
fi
# Check if this swap space is already setup for encryption
if /sbin/dmsetup table "$swap" 2>/dev/null | grep -qs " crypt "; then
warn "[$swap]" `gettext "already appears to be encrypted, skipping."`
continue
fi
base=$(basename "$swap")
if grep -qs "^$base.*swap.*cipher" /etc/crypttab 2>/dev/null; then
warn "[$swap]" `gettext "already has an entry in /etc/crypttab, skipping."`
continue
fi
if grep -qs "$swap" /etc/initramfs-tools/conf.d/cryptroot 2>/dev/null; then
warn "[$swap]" `gettext "already has an entry in /etc/crypttab, skipping."`
continue
fi
echo $swap
done
)
swaps="$filtered_swaps"
if [ -z "$swaps" ]; then
warn "There were no usable swap devices to be encrypted. Exiting."
exit 0
fi
##########################################################################
# Warn the user about breaking hibernate mode
if [ "$FORCE" != 1 ]; then
echo
echo `gettext "WARNING:"`
echo `gettext "An encrypted swap is required to help ensure that encrypted files are not leaked to disk in an unencrypted format."`
echo
echo `gettext "HOWEVER, THE SWAP ENCRYPTION CONFIGURATION PRODUCED BY THIS PROGRAM WILL BREAK HIBERNATE/RESUME ON THIS SYSTEM!"`
echo
echo `gettext "NOTE: Your suspend/resume capabilities will not be affected."`
echo
echo -n `gettext "Do you want to proceed with encrypting your swap?"` "[y/N]: "
CONFIRM=`head -n1`
echo
if [ "$CONFIRM" != "y" -a "$CONFIRM" != "Y" ]; then
echo
info `gettext "Aborting."`
echo
exit 0
fi
fi
##########################################################################
i=0
for swap in $swaps; do
info `gettext "Setting up swap:"` "[$swap]"
uuid=$(blkid -o value -s UUID $swap)
for target in "UUID=$uuid" $swap; do
if [ -n "$target" ] && grep -qs "^$target " /etc/fstab; then
sed -i "s:^$target :\#$target :" /etc/fstab
warn "Commented out your unencrypted swap from /etc/fstab"
fi
done
while :; do
i=$((i+1))
[ -e "/dev/mapper/cryptswap$i" ] || break
done
# Add crypttab entry
echo "cryptswap$i $swap /dev/urandom swap,cipher=aes-cbc-essiv:sha256" >> /etc/crypttab
# Add fstab entry
echo "/dev/mapper/cryptswap$i none swap sw 0 0" >> /etc/fstab
done
if [ "$NO_RELOAD" != 1 ]; then
# Turn swap off
swapoff -a
# Restart cryptdisks
/etc/init.d/cryptdisks restart
# Turn the swap on
swapon -a
fi
info `gettext "Successfully setup encrypted swap!"`