Updating with a delta file linux
On Unix-like operating systems, the rsync command synchronizes files from a source to a destination, on a local machine or over a secure network connection.It is a fast, flexible, secure replacement for the command rcp.rsync is widely used for backups and mirroring and as an improved copy command for everyday use.rsync finds files that need to be transferred using a "quick check" algorithm (by default) that looks for files that have changed in size or in last-modified time.This option is useful when invoking rsync from cron.
Generating the checksums means that both sides will expend a lot of disk I/O reading all the data in the files in the transfer (and this is prior to any reading that will be done to transfer changed files), so this can slow things down significantly.
Any changes in the other preserved attributes (as requested by options) are made on the destination file directly when the quick check indicates that the file's data does not need to be updated.
Some of the additional features of rsync are: rsync accepts both long (double-dash word) and short (single-dash letter) options.
When specifying a parameter, you can either use the form --option=param or replace the ’=’ with whitespace.
The parameter may need to be quoted in some manner for it to survive the shell's command-line parsing.
Keep in mind that a leading tilde (~) in a file name is substituted by your shell, so --option=~/foo will not change the tilde into your home directory (remove the ’=’ for that).