this
- author:
david.villa
- Follow @david_vi11a
- created: 2011-04-04
- source / edit
- categories: recipe
- migrated from node/1489
- tags: networking
The poor's man "dropbox"-thing
This recipe shows how to setup a basic synchronization mechanism (similar to DropBox) by means of conventional GNU/Linux tools. This does not require root privileges and no packages (except ssh-server) need to be installed in the server.
WARNING: This procedure may cause data loss. Use it under your responsibility
Ingredients
In the client:
- cron
- incron
In the server:
- ssh server
The server should be accessible from everywhere and configured for using ssh public key authentication. Nothing else needs to be modified in your server.
The “poorbox” script
Put that in your ~/bin/poorbox.sh:
#!/bin/bash --
# poorbox.sh {to-host|to-server} [file EVENT]
set -e
SERVER=server
USER=john
FOLDER=PoorBox/
LOCAL=/home/$USER/$FOLDER
REMOTE=$SERVER:$FOLDER
case $1 in
"to-host")
SOURCE=$REMOTE
TARGET=$LOCAL
;;
"to-server")
SOURCE=$LOCAL
TARGET=$REMOTE
;;
* )
echo "usage: $0 [to-host|to-server]"
exit 1
esac
LOCK=/tmp/$USER.poorbox
# avoid reentrant execution
flock -n $LOCK-$1 true
if [ "$3" == "IN_DELETE" ]; then
CMD="ssh $SERVER rm $FOLDER$2"
else
CMD="rsync -avz --delete $SOURCE$2 $TARGET"
fi
# wait for the inverse transfer
flock $LOCK $CMDSynchronizing host to server
The next configuration will copy or delete any modified file from your laptop/PC to your server account. First, you need to put your username in the /etc/incron.allow file.
Run that in a terminal:
$ incrontab -eYour default editor will start. Write down next line, save and close.
/home/john/PoorBox IN_MODIFY,IN_DELETE,IN_CLOSE_WRITE,IN_MOVE /home/john/bin/poorbox.sh to-server $# $%and then:
$ incrontab -dSynchronizing host from server
We will not detect changes in server files (although may be possible using the same way). We will poll changes using cron. Run next in a console:
$ crontab -ewrite and save next line:
*/1 * * * * /home/john/bin/poorbox.sh to-hostThis poll each minute. Of course, you may increase or decrease the polling frequency as you prefer.
Improving performance
Continuous ssh connections does not seems a good idea, but it is possible tweak your config by means of ControlMaster and KeepAlive ssh options.
Limitations
Currently incron does not detect recursive events (operations on subdirectories)