The default order can be customized by setting the environment variable RSYNCCHECKSUMLIST to a space-separated list of acceptable checksum names. However, this incurs in a large overhead due to the checksum operations done in the remote machine. This is done by first running rsync while the database server is running, then shutting down the database server long enough to do an rsync -checksum. If the remote rsync is too old to support checksum negotiation, a value is chosen based on the protocol version (which chooses between MD5 and various flavors of MD4 based on protocol age). Rsync -avz -delete $BASEPATH/upload/ would be possible to directly perform the synchronization between the local public/ directory and the remote server using the checksum method. Rsync -r -delete -checksum $BASEPATH/public/ $BASEPATH/upload/ The following sync.sh bash script does all the work: #!/bin/bashīASEPATH=/your-path-to-local-hugo-base-directory/ In this way, the files in the upload/ directory are updated only when there is an actual change in the content within the public/ directory.Īfterwards, I can use the usual remote synchronization method between the local upload/ directory and the remote server using the modification times. The synchronization is not done by modification date, but by file checksum, which is one of the methods provided by rsync. The upload/ directory is kept synchronized with the Hugo’s public/ directory. erty that it is very cheap to calculate the checksum of a. I have a local directory called upload/, which is located in the same Hugo base directory. The weak rolling checksum used in the rsync algorithm needs to have the prop. To limit this problem, I use this workaround. This option changes this to compare a 128- bit checksum for each file with a matching size. Without this option, rsync uses a 'quick check' that (by default) checks if each file's size and time of last modification match between the sender and receiver. This happens because Hugo regenerates all the files at every local build.įor this reason, when rsync checks the changes in the modification times between local and remote files, the local ones are all always newer, and thus all of them are uploaded remotely. This changes the way rsync checks if the files were changed and are in need of a transfer. In particular, everytime I rebuild the local copy of the site with Hugo, and I run the command to synchronize the remote copy, all the local files are uploaded to the server. During the second run, gsutil reports that it is computing. To ensure that I have all of the requested files, I run gsutil a second time with checksums turned on.
![rsync checksum rsync checksum](https://untitled.pw/wp-content/uploads/2019/02/QQ20190209-233424@2x-1024x836.png)
#Rsync checksum download#
Occasionally the download fails for a few files. rsync does it in O(n) time instead of O(n m) time, where n is the size of the file and m is the window size). I am downloading a large number of public data files from Google Cloud Storage using gsutil rsync.
![rsync checksum rsync checksum](https://www.epiphan.com/userguides/pearl-nano/Content/Resources/Images/screencaps/WebUI/web_rsync-config.png)
#Rsync checksum update#
After having moved to Hugo for my personal website, I found that the usual way of using rsync to update the copy of the website on the remote server does not work efficiently. rsync's weak-hash algorithm is specifically designed to work on a rolling-basis (such that you can push-and-pop individual byte values) instead of reiterating the window on every byte (i.e.