How can I exclude files by default with rsync?

Add your excludes to a file, then use --exclude-from=/path/to/exclude_file

e.g.

# cat rsync.excludes
.ht*
error_log
.DS*
old
...

# rsync --exclude-from=rsync.excludes

No, rsync does not have a default configuration file that it will read upon invocation. The best you can do is what @frogstarr78 says and create a text file with patterns, file and directory names to exclude, and then point rsync to it with --exclude-from=filename.

While rsync doesn't let you set default options, you can create a wrapper script and put it higher up in your $PATH than the rsync binary.

This is is my rsync wrapper which lives in ~/bin/rsync

#!/bin/sh

# Set path to the rsync binary
RSYNC=/usr/bin/rsync

# Look for these exclude files
IGNORE_FILES=(~/.rsyncignore ./.gitignore ./.rsyncignore)

EXCLUDE_FROM=""
for f in ${IGNORE_FILES[@]}; do
  if [[ -e $f ]]; then
    EXCLUDE_FROM="$EXCLUDE_FROM --exclude-from=$f "
  fi
done
$RSYNC $EXCLUDE_FROM "$@"

It'll look for ~/.rsyncignore, ./.gitignore, ./.rsyncignore files and, if any of them exist, use them as default --exclude-from arguments.

Just change the RSYNC and IGNORE_FILES to suit your envrionment and preferences.