rsync cheat sheet

Things I use rsync for:

deploy static webpage to server: rsync -rvzlpt --delete "out/" "user@myserver:/path/to/served/folder/"
backing up pictures onto my HDD: rsync -av "/path/to/pictures/folder/picts/" "/path/to/mounted/disk/picts/"

rsync is a good program for these tasks because it will only copy the file if it changed.

Connecting to servers is done with ssh. If you can ssh user@server you can rsync user@server:/some/path.

flags

rsync -v: print which file is being worked on
rsync -z: use compression in transit (really useful when copying files over the internet)
rsync --dry-run: don’t actually write anything to the destination
rsync --delete: delete files at the destination that no longer exist at the source

the -a flag is “archive mode”, which enables all of -rlptgoD:

rsync -r: recursive
rsync -l: copy symlinks as symlinks
rsync -p: copy the permission bits
rsync -t: copy the modification times
rsync -g: copy owning group id
rsync -o: copy owning user id
rsync -D: copy devices and copy “specials” (named sockets and fifos? character and block devices?)

Some of this is overkill unless you’re doing “backups”; and copying from one computer to another can result in nonsense group/ownership information if the computers don’t have their groups and users set up exactly the same way.

trailing slashes

let’s say we have a file at /path/to/source/hello.txt

rsync path/to/source/ path/to/dest will create the file path/to/dest/hello.txt
rsync path/to/source path/to/dest will create the file path/to/dest/source/hello.txt

A trailing slash on the source is usually what you want. No-trailing-slash is more like “dragging-and-dropping source into dest using a graphical file manager.”

trailing slash on the destination

For completeness, even though this only makes a difference iff the source is a file and the dest doesn’t exist, which is kind of a weird way to use rsync:

rsync path/to/source/hello.txt path/to/dest/ will create the directory path/to/dest and put the file path/to/dest/hello.txt inside
rsync path/to/source/hello.txt path/to/dest will create the file path/to/dest with the contents of hello.txt

i.e.

if there is a trailing slash, it will create a directory with that name and copy the file inside
if there is no trailing slash, it copies the file to dest (basically it acts like cp)

cp would error in the first case (copying to a trailing-slashed path). rsync is implementing a “do what i mean” behavior here

Termux

Copying from Termux onto a normal computer is probably going to mangle the permission bits and owning group/user information on the destination. (Termux runs under some weird umasks, and rsync dutifully copies them.)

I work around this with an ssh dest_computer "chmod +rX -R /path/to/dest/; chown owning_user:owning_group -R /path/to/dest/" lmao, kind of a sledgehammer but it works.

TODO: Maybe rsync --super will also help (“This tells the receiving side to attempt super-user activities even if the receiving rsync wasn’t run by the super-user”)