TOPIC: RSYNC
Getting rsync to resolve symbolic links
11th September 2024Given how Dropbox changed its handling of symbolic links in 2019 such that internal links within a Dropbox file hierarchy got fixed and links leading outside from the Dropbox area no longer worked. Thankfully, the rsync utility found in many Linux and UNIX settings does not do that, as long as you have called it correctly.
By default, symbolic links are synchronised like any other file. That is what Dropbox does now. To get rsync to resolve the links as shortcuts to either a single file or more likely a folder containing more than one file, it needs the -L switch or option in the command. When that is present, the linked file or files will get synchronised and honours the point of having these links in the first place: allowing more flexibility with folder structures and avoiding any duplication of files and folders.
Avoiding permissions, times or ownership failure messages when using rsync
22nd April 2023The rsync command is one that I use heavily for doing backups and web publishing. The latter means that it is part of how I update websites built using Hugo because new and/or updated files need uploading. The command also sees usage when uploading files onto other websites as well. During one of these operations, and I am unsure now as to which type is relevant, I encountered errors about being unable to set permissions.
The cause was the encompassing -a option. This is a shorthand for -rltpgoD, and the individual options perform the following:
-r: recursive transfer, copying all contents within a directory hierarchy
-l: symbolic links copied as symbolic links
-t: preserve times
-p: preserve permissions
-g: preserve groups
-o: preserve owners
-D: preserve device and special files
The solution is to some of the options if they are inappropriate. The minimum is to omit the option for permissions preservation, but others may not apply between different servers either, especially when operating systems differ. Removing the options for preserving permissions, groups and owners results in something like this:
rsync -rltD [rest of command]
While it can be good to have a more powerful command with the setting of a single option, it can mean trying to do too much. Another way to avoid permissions and similar errors is to have consistency between source and destination files systems, but that is not always possible.
Copying only updated new or updated files by command line in Linux or Windows
2nd August 2014With a growing collection of photographic images, I often find myself making backups of files using copy commands and the data volumes are such that I don't want to keep copying the same files over and over again, so incremental file transfers are what I need. So commands like the following often get issued from a Linux command line:
cp -pruv [source] [destination]
Because this is on Linux, it is the bash shell that I use, so the switches may not apply with others like ssh, fish or ksh. For my case, p preserves file properties such as its time and date and the cp command does not do this always, so it needs adding. The r switch is useful because the copy then in recursive, so only a directory needs to be specified as the source and the destination needs to be one level up from a folder with the same name there to avoid file duplication. It is the u switch that makes the file copy incremental, and the v one issues messages to the shell that show how the copying is going. Seeing a file name issued by the latter does tell you how much more needs to be copied and that the files are going where they should.
What inspired this post though is my need to do the same in a Windows session, and issuing xcopy commands will achieve the same end. Here are two that will do the needful:
xcopy [source] [destination] /d /s
xcopy [source] [destination] /d /e
In both cases, it is the d switch that ensures that the copy is incremental, and you can add a date too, with a colon between it and the /d, if you see fit. The s switch copies only directories that contain files, while the e one copies even empty directories. Using the d switch without either of those did not trigger any copying action when I tried, so I reckon that you cannot do without either of them. By default, both of these commands issue output to the command line so you can keep an eye on what is happening, and this especially is useful when ensuring that files are going to the right destination because the behaviour differs from that of the bash shell on Linux.