Question 1

Why does the trailing slash on the source matter so much in rsync?

Accepted Answer

It is the #1 rsync footgun. `rsync -a src/ dest/` copies the CONTENTS of src/ into dest/ (so dest/file.txt). `rsync -a src dest/` (no trailing slash) copies the src DIRECTORY itself into dest/ (so dest/src/file.txt). The trailing slash on the DESTINATION is generally irrelevant. This builder visualizes exactly what lands where for both source variants so you can verify before you run.

Question 2

How does this builder handle the dangerous --delete flag?

Accepted Answer

rsync --delete removes files in the destination that no longer exist in the source — it is genuinely dangerous and a frequent cause of data loss. The builder always recommends --dry-run alongside --delete (a red badge + nudge), warns when --delete is enabled without --dry-run, and shows a tip about --delete-excluded (which also deletes excluded files in dest, even more dangerous). The default archive mode (-a) preserves perms, times, ownership, symlinks, devices; --delete only adds removal of missing files.

Question 3

How do I sync over SSH with a custom key and port?

Accepted Answer

Use -e 'ssh -i ~/.ssh/key -p 2222' (single-quoted so the inner flags are passed to ssh verbatim). For a push: `rsync -avz -e 'ssh -i ~/.ssh/key -p 2222' ./local/ user@host:/remote/path/`. For a pull, swap source and destination: `rsync -avz -e 'ssh -i ~/.ssh/key -p 2222' user@host:/remote/path/ ./local/`. The builder builds the -e string for you from the SSH key, port, and extra ssh options fields.

Question 4

What does -a (archive mode) actually do?

Accepted Answer

-a is shorthand for -rlptgoD: r=recursive, l=symlinks (copy as symlinks), p=permissions, t=times (mtime), g=group, o=owner (needs root), D=devices+specials (needs root). It does NOT include -H (hard links), -A (ACLs), -X (xattrs), or -z (compression). The builder's explanation panel breaks down each sub-flag so you know exactly what -a buys you and what you might want to add.

Question 5

What extra features does this tool have?

Accepted Answer

(1) Direction selector — local, push (local→remote), pull (remote→local). (2) Trailing-slash visualizer showing what lands where. (3) 9 toggle flags — archive, verbose, compress, human-readable, progress, partial, checksum, numeric-ids, dry-run. (4) --delete and --delete-excluded (guarded, with dry-run nudge). (5) Excludes list + --exclude-from file. (6) Bandwidth limit (--bwlimit KB/s). (7) SSH transport builder — key, port, extra ssh options. (8) Preserve-detail breakdown of -a as -rlptgoD. (9) Per-flag plain-English explanation. (10) Recipe library (10 common one-liners). (11) Shell-quoting of paths and SSH strings. (12) Copy command + download. (13) localStorage history (max 20). (14) Shareable URL with embedded config. 100% client-side — commands are generated, never executed.

rsync Command Builder

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How to use

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