Created
August 9, 2012 00:28
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bash: ram disk and trap shutdown
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#!/bin/bash | |
# Auto-filled variables | |
USER_NAME=$(/usr/bin/who am i | /usr/bin/awk '{print $1}') | |
SELF=$(/usr/bin/basename $0) | |
USER_ID=$(id | sed 's/uid=\([0-9]*\).*/\1/') | |
OUR_PID=$(ps -ef | grep ${SELF} | grep -v 'grep' | awk -v uid="$USER_ID" '$1==uid {print $2; exit;}') # Only first occurence from the current user. | |
# Constants | |
RSYNC="/usr/bin/rsync -aNHAXx --fileflags --protect-decmpfs " | |
SLEEP_DELAY=1 | |
let SAFETY_BACKUP_INTERVAL=(60*60*2)/SLEEP_DELAY # Create backup in case of power failure every 2 hours. | |
# Settings | |
RAMDISK_SIZE=256 # Size in Mega Bytes. | |
RAMDISK_NAME="RamDisk" | |
SNAPSHOT_LOCATION="/Users/${USER_NAME}/Library/CachesSnapshot${RAMDISK_NAME}/" | |
# Variables | |
COUNT= | |
# Operational function declaration | |
function log | |
{ | |
echo "${SELF}: $1" | |
} | |
function quit | |
{ | |
log "Quiting: $1" | |
exit 0 | |
} | |
function lock_ramdisk | |
{ | |
exec 5>"/Volumes/${RAMDISK_NAME}/.lock.${USER_NAME}" | |
} | |
function unlock_ramdisk | |
{ | |
exec 5>&- | |
rm "/Volumes/${RAMDISK_NAME}/.lock.${USER_NAME}" | |
} | |
function create_ramdisk | |
{ | |
# Check if ramdisk is not already created and mounted. | |
if [ ! -d "/Volumes/${RAMDISK_NAME}" ]; then | |
log "Creating Ram disk (\"${RAMDISK_NAME}\") with a size of: ${RAMDISK_SIZE}MB." | |
let RAMDISK_BLOCKSIZE=2048*${RAMDISK_SIZE} # Size in blocks. | |
BLOCK_DEVICE=$(hdiutil attach -nomount ram://${RAMDISK_BLOCKSIZE}) | |
diskutil eraseVolume HFS+ "$RAMDISK_NAME" $BLOCK_DEVICE | |
# Update so every user can write to it while pertaining its own | |
# user permissions. | |
mount -u -o owners "/Volumes/${RAMDISK_NAME}" | |
chmod g+w "/Volumes/${RAMDISK_NAME}" | |
else | |
log "Ram disk (\"${RAMDISK_NAME}\") already created." | |
fi | |
} | |
function restore_contents_from_snapshot | |
{ | |
# Check if snapshot exists | |
if [ -d ${SNAPSHOT_LOCATION} ]; then | |
DEST="/Volumes/${RAMDISK_NAME}/${USER_NAME}/" | |
log "Restoring snapshot from \"${SNAPSHOT_LOCATION}\" to \"${DEST}\"." | |
$RSYNC "${SNAPSHOT_LOCATION}" "${DEST}" | |
else | |
log "No restore required: \"${SNAPSHOT_LOCATION}\" not found." | |
fi | |
} | |
function store_contents_on_snapshot | |
{ | |
SOURCE="/Volumes/${RAMDISK_NAME}/${USER_NAME}/" | |
if [ ! -d "$SOURCE" ]; then | |
quit "Directory: \"$SOURCE\" does not exist." | |
fi | |
log "Storing snapshot from \"${SOURCE}\" to \"${SNAPSHOT_LOCATION}\"." | |
$RSYNC "${SOURCE}" "${SNAPSHOT_LOCATION}" | |
} | |
function store_periodically | |
{ | |
let COUNT=COUNT+1 | |
if [ "0$COUNT" -gt $SAFETY_BACKUP_INTERVAL ]; then | |
log "Starting power failure preventive backup." | |
store_contents_on_snapshot | |
let COUNT=0 | |
fi | |
} | |
function shutdown | |
{ | |
log "Shutdown request received." | |
store_contents_on_snapshot | |
unlock_ramdisk | |
quit "Shutdown request finished." | |
} | |
# Shutdown: Register terminate signals. | |
trap shutdown TERM | |
# Startup | |
create_ramdisk | |
lock_ramdisk | |
restore_contents_from_snapshot | |
# Renice ourself to a low priority | |
log "Lowering priority from $OUR_PID to 19." | |
/usr/bin/renice 19 ${OUR_PID} | |
# Main loop | |
while [ 1 ]; do | |
sleep ${SLEEP_DELAY} | |
# Store to snapshot every hour for extra safety (power failure, etc.) | |
store_periodically | |
done |
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