BIPEDU

my ideas in action

FTP backup with BASH script ( FTP scripting)

FTP protocol is used to transfer data between computers. The user has also a possibility to combine bash scripts with FTP to automate the backups of the files. This concept can be used for example to backup some files from a local machine to a remote server.
The way to do this is by making an executable script that is run from time to time by a cron job task. In this way the backup is made automatically in the background and do not require user intervention. But there is a problem. if you use FTP in command line then you have to type user name and password in clear text. So how to do it ?
The solution I suggest is like in the example below:

First step is to determine if the backup is needed . We check if the file was changed since last backup. For this we use a compare between the size of the file in this moment with the size of the file at the previous backup time. The previous size was saved in a file. To check this we use the “if compare” structure from BASH:

### check if the file was changed, and if YES then make FTP transfer, if not exit
 if [ `cat ~/.size_myfile.txt` -ne `du -s /path/to/file | cut -f1` ] ; then
 echo 'File changed !'
 fi
 ###########################

Then we define some parameters for FTP command. This definition can be made in a different ( hidden) file. For not critical situations ( home users) I recommend keeping the user details in the same file ( in the script) but to remove all the permissions for the other users ( use chmod command ). So the backup script should look like this:

-rwx------ myuser mygroup 32 june 12 14:52 backupFTP.script

Notice that only the “myuser” user has the right to read/write/execute the file

So for FTP command you need:

##############################
 HOST='ftp.myserver.com'
 USER='myusername'
 PASSWD='mypassword'
 FILE='/path/to/filesource filedestination'
ftp -n $HOST <<END_SCRIPT
 quote USER $USER
 quote PASS $PASSWD
 cd /path/to/destination
 put $FILE
 quit
 END_SCRIPT
 #############################

Since the source path and the destination path may be different you can use “cd /path/to/destination” for the file. The copied file can be also renamed as shown above ( see “filedestination“)

Notice that the commands between “END_SCRIPT” tags are executed inside FTP terminal. This are FTP commands and not BASH/Linux commands. You can put here whatever FTP commands you want based on your needs. For a full list of the FTP commands type “help” in the FTP terminal.

The 3rd step is to recalculate and save the new size of the file so that next time when backup script is run the size file is updated. For this we do:

################################
 ## recalculate the new size of the file, for next backup
 du -s /path/to/file | cut -f1 > ~/.size_myfile.txt
 env DISPLAY=:0 notify-send 'FTP backup done !' 'File : /path/to/file'
 ###############################

Optionally you can show a desktop notification that the backup was made. If you do not have a GUI then do not use it.

Next I show the full script in only one file:

#!/bin/bash
 ### check if the file was changed, and if YES then make FTP transfer, if not exit
 if [ `cat ~/.size_myfile.txt` -ne `du -s /path/to/file | cut -f1` ] ; then
#    echo 'File changed !'
 sleep 1
 #
 HOST='ftp.myserver.com'
 USER='myusername'
 PASSWD='mypassword'
 FILE='/path/to/filesource filedestination'
 ftp -n $HOST <<END_SCRIPT
 quote USER $USER
 quote PASS $PASSWD
 cd /path/to/destination
 put $FILE
 quit
 END_SCRIPT
 sleep 1
 ## recalculate the new size of the file, for next backup
 du -s /path/to/file | cut -f1 > ~/.size_myfile.txt
 env DISPLAY=:0 notify-send 'FTP backup done !' 'File : /path/to/file'
fi
 ###############
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