Create AWS AMIs from Scratch

tmpfsroot-el6.sh

#!/bin/bash
#
# Pivot the root partition to a tmpfs mount point so that the root volume can
# be re-partitioned.
#
##############################################################################
set -x
set -e

# Prevent selinux from interfering
setenforce 0 || true

# Stop all services we do not need
telinit 2
for SERVICE in $(
    chkconfig --list | \
    grep 2:on | \
    awk '{print $1}' | \
    grep -v \
        -e cloud-init \
        -e cloud-config \
        -e cloud-final \
        -e sshd \
        -e network \
        -e rawdevices
    )
do
    service $SERVICE stop || true
done

# Unmount as much as possible
umount -a || true

# Create tmpfs mount
mkdir /tmp/tmproot
mount -t tmpfs none /tmp/tmproot

# Copy everything to the tmpfs mount
cp -ax / /tmp/tmproot
cp -a /dev /tmp/tmproot

# Switch / to tmpfs
mkdir /tmp/tmproot/oldroot
mount --make-rprivate /
pivot_root /tmp/tmproot /tmp/tmproot/oldroot
mount none /proc -t proc
mount none /sys -t sysfs
mount none /dev -t devtmpfs
mount none /dev/pts -t devpts
mount none /selinux -t selinuxfs

# Stop services holding /oldroot
#   Note: Do not do this in an interactive shell because you will probably
#   kill your session. Instead, just use `fuser -vm /oldroot` to identify
#   processes holding /oldroot and kill them by name with `killall <name>`.
#   Then restart ssh, reconnect to a new session, and close your old session.
kill -9 $(fuser -vm /oldroot 2> /fuser.log | sed "s/\b$$\b//") || true

# Kill and reload init to free /oldroot
killall init && telinit u

# Unmount everything on /oldroot
for MOUNT in $(
    cat /proc/mounts | \
    cut -d ' ' -f 2 | \
    grep '/oldroot/' | \
    sort -ru
    )
do
    umount $MOUNT || true
done

# /oldroot/dev needs a lazy unmount
umount -l /oldroot/dev || true
umount -l /oldroot/dev || true # Often there are two devtmpfs mounts

# Attempt final unmount of /oldroot; this will probably fail since the process
# running this script is still open. A follow-on script or interactive shell
# can check and issue the final umount (works well with packer).
umount /oldroot || true

# Restart udevd; required to create lvm volumes
/sbin/start_udev

# Change ssh port. Set packer to connect to port 122; this way packer waits
# until this script is complete.
sed -i -e "s/^[#]*Port .*$/Port 122/" /etc/ssh/sshd_config
service sshd restart