How to automatically snapshot a volume of an Amazon EC2 instance?

I’m trying a script to backup a volume automatically.

I follow this EBS-Snapshot.sh script as found on github:

#!/bin/bash

# export EC2_HOME='/etc/ec2'  # Make sure you use the API tools, not the AMI tools
# export EC2_BIN=$EC2_HOME/bin
# export PATH=$PATH:$EC2_BIN
# I know all of the above is good to have solution, but not re-usable
# I have captured all of the above in a particular file and lemme execute it
source /etc/environment

PURGE_SNAPSHOT_IN_DAYS=10

EC2_BIN=$EC2_HOME/bin

# store the certificates and private key to your amazon account
MY_CERT='/path/to/certificate-file'
MY_KEY='/path/to/private-file'
# fetching the instance-id from the metadata repository
MY_INSTANCE_ID='your ec2-instance-id'

# temproary file
TMP_FILE='/tmp/rock-ebs-info.txt'

# get list of locally attached volumes via EC2 API:
$EC2_BIN/ec2-describe-volumes -C $MY_CERT -K $MY_KEY > $TMP_FILE
VOLUME_LIST=$(cat $TMP_FILE | grep ${MY_INSTANCE_ID} | awk '{ print $2 }')

sync

#create the snapshots
echo "Create EBS Volume Snapshot - Process started at $(date +%m-%d-%Y-%T)"
echo ""
echo $VOLUME_LIST
for volume in $(echo $VOLUME_LIST); do
   NAME=$(cat $TMP_FILE | grep Name | grep $volume | awk '{ print $5 }')
   DESC=$NAME-$(date +%m-%d-%Y)
   echo "Creating Snapshot for the volume: $volume with description: $DESC"
   echo "Snapshot info below:"
   $EC2_BIN/ec2-create-snapshot -C $MY_CERT -K $MY_KEY -d $DESC $volume
   echo ""
done

echo "Process ended at $(date +%m-%d-%Y-%T)"
echo ""

rm -f $TMP_FILE

#remove those snapshot which are $PURGE_SNAPSHOT_IN_DAYS old

I have the two files for X509 authentication, the instance ID but I don’t understand the script and how to parameterise the volume that I want to backup.

I don’t understand the first line (source) and the EC2_BIN. With that configuration, it lists all the volumes and makes a snapshot of all these…

For the comment of the snapshot, how can I change this line to add text?

DESC=$NAME-$(date +%m-%d-%Y)

I’m sorry to be a beginner but I don’t understand the whole script

EDIT :

I get this error with this new code:

Creating Snapshot for the volume: ([ec2-describe-volumes]) with description: -03-13-2012 Snapshot info below: Client.InvalidParameterValue: Value (([ec2-describe-volumes])) for parameter volumeId is invalid. Expected: ‘vol-…’. Process ended at 03-13-2012-08:11:35 –

And this is the code :

#!/bin/bash

#Java home for debian default install path:
export JAVA_HOME=/usr
#add ec2 tools to default path
#export PATH=~/.ec2/bin:$PATH


#export EC2_HOME='/etc/ec2'  # Make sure you use the API tools, not the AMI tools
export EC2_BIN=/usr/bin/
#export PATH=$PATH:$EC2_BIN
# I know all of the above is good to have solution, but not re-usable
# I have captured all of the above in a particular file and lemme execute it
source /etc/environment

PURGE_SNAPSHOT_IN_DAYS=60

#EC2_BIN=$EC2_HOME/bin

# store the certificates and private key to your amazon account
MY_CERT='cert-xx.pem'
MY_KEY='pk-xx.pem'
# fetching the instance-id from the metadata repository

MY_INSTANCE_ID=`curl http://169.254.169.254/1.0/meta-data/instance-id`

# temproary file
TMP_FILE='/tmp/rock-ebs-info.txt'

# get list of locally attached volumes via EC2 API:
$EC2_BIN/ec2-describe-volumes -C $MY_CERT -K $MY_KEY > $TMP_FILE

#VOLUME_LIST=$(cat $TMP_FILE | grep ${MY_INSTANCE_ID} | awk '{ print $2 }')
VOLUME_LIST=(`ec2-describe-volumes --filter attachment.instance-id=$MY_INSTANCE_ID | awk '{ print $2 }'`)

sync

#create the snapshots
echo "Create EBS Volume Snapshot - Process started at $(date +%m-%d-%Y-%T)"
echo ""
echo $VOLUME_LIST
echo "-------------"
for volume in $(echo $VOLUME_LIST); do
   NAME=$(cat $TMP_FILE | grep Name | grep $volume | awk '{ print $5 }')
   DESC=$NAME-$(date +%m-%d-%Y)
   echo "Creating Snapshot for the volume: $volume with description: $DESC"
   echo "Snapshot info below:"
   $EC2_BIN/ec2-create-snapshot -C $MY_CERT -K $MY_KEY -d $DESC $volume
   echo ""
done

echo "Process ended at $(date +%m-%d-%Y-%T)"
echo ""

rm -f $TMP_FILE

#remove those snapshot which are $PURGE_SNAPSHOT_IN_DAYS old

Answer

Ok well,

1. The first line where he runs (source). Thats the same as . /etc/environment. Anyways all he’s doing is loading a file that has a list of environmental variables that amazon requires. At least this is what i assume.
2. He’s making this script much more complicated than it needs to be. He doesn’t need to run the ec2-describe-instances command and save the output to a file then grep the output etc….
3. You can put whatever you want for the DESC. You can just replace everything to the right of the = to whatever text you want. Just make sure to put quotes around it.

I would change two things about this script.

1. Get the InstanceId at runtime in the script. Don’t hard code it into the script. This line will work no matter where the script is running.

   MY_INSTANCE_ID=`curl http://169.254.169.254/1.0/meta-data/instance-id`
   

2. Instead of calling ec2-describe-volumes and saving the output to a temp file etc… Just use a filter on the command and tell it which instance id you want.

   VOLUME_LIST=(`ec2-describe-volumes --filter attachment.instance-id=$MY_INSTANCE_ID | awk '{ print $2 }'`)