Cyberduck With a Seedbox: Setup, Segmented Downloads, and the Catch

Cyberduck works well with a seedbox: it speaks SFTP, it is free on macOS and Windows, and — unusually for a free client — it splits any download over 100 MB across several connections by default. The catch comes after the pieces arrive: Cyberduck stores them as separate segments and then runs a merge step that its own documentation says “may take a considerable amount of time” and that cannot finish if any part is missing. On a seedbox, where nearly everything you pull is multi-gigabyte, that merge is the difference between “done when the bar fills” and “done a while later, if nothing went wrong”.

That gap is what evoftp, our free SFTP client, was built to close: it segments every large file the same way but writes the segments straight into place, so there is nothing to merge and a cancelled download resumes from a small sidecar file. Cyberduck is still the better general-purpose tool; here is how to set it up for a seedbox, where its limits are, and when switching is worth it.

At a glance

Setting up Cyberduck for a seedbox

Your seedbox accepts SFTP on port 22 with your client-area username and password; the SFTP setup guide shows where to find them. In Cyberduck:

1. Open Bookmarks → Toggle Bookmarks (⌘B on macOS, Ctrl+B on Windows) and click + in the lower-left corner.
2. Protocol: SFTP (SSH File Transfer Protocol), not FTP — SFTP is encrypted and is the protocol to use for a seedbox in Cyberduck and evoftp alike.
3. Server: the hostname shown in your client area. Port: 22.
4. Username and Password: your seedbox login. Cyberduck keeps the password in Keychain on macOS or Credential Manager on Windows.
5. Path: leave empty to land in your home directory. Torrent data is in downloads; a .torrent dropped into downloads/watch is added to rTorrent.
6. Download Folder: where seedbox files land locally.
7. Transfer Files: Open new connection, not Use browser connection, so browsing stays responsive during a big transfer.

Double-click the bookmark, accept the host key fingerprint on first connect, and you are in.

The transfer-window connection cap

A control in the Transfers window caps open connections, and that one number covers parallel transfers, the connections a segmented download uses, and multi-file transfers together. Once hit, queued rows show Maximum allowed connections exceeded. Waiting…. The documentation states neither the default nor the segment count, so if downloads feel slow, raise this number first; eight is sensible for a seedbox.

Existing-file actions

When a download meets a file that already exists locally, Cyberduck offers Overwrite, Compare (skip if checksum or modification date match), Resume (append the missing tail), Rename, Rename existing (timestamp on the new or the old file) and Skip. For a seedbox, Compare is the safe default: it stops you re-pulling a season pack because one episode was already there.

What the merge step means in practice

Cyberduck’s download page puts it plainly: “Merging the segments may take a considerable amount of time”, and “if some parts are missing the downloaded segments are saved within a folder and the file can’t be restored unless you redownload the file or try to Resume the failed transfer.”

So 100% on the progress bar is not the end — on a 40 GB remux the merge is a second pass over the whole file, and you need local free space for it twice. A dropped Wi-Fi link leaves a folder of segments, not a partial file; the way out is Resume on the failed row, which survives a restart. Do not delete the segment folder first.

Where Cyberduck is better

• Protocols. WebDAV, SMB, S3 and the mainstream cloud drives in one app. evoftp stops at SFTP, FTPS and FTP.
• Mounting. Its paid sibling Mountain Duck mounts server and cloud storage as a disk in Finder or File Explorer (14-day trial). evoftp cannot mount anything; the free route is mounting your seedbox with sshfs.
• Bookmark import. Picks up bookmarks from Transmit, FileZilla and WinSCP automatically. evoftp has no importer.
• Sync and remote edit. Mirror or one-way sync with a preview, and edit-and-reupload with any editor. evoftp has neither.
• Maturity and signing. Sold through the Mac App Store and Windows Store, so it opens without a Gatekeeper or SmartScreen workaround. evoftp is 0.2.0, not yet signed or notarised: right-click → Open on macOS, “Run anyway” on Windows.
• macOS password storage. Cyberduck uses Keychain; the unsigned evoftp macOS build stores a saved password unencrypted in its config folder, so leave the field empty if that bothers you.
• Bandwidth throttling and a transfer history that survives restarts. evoftp has neither.

Where evoftp is better

• No merge step. Segments are written directly into their final byte range of one file, the same technique as lftp pget -n. When the bar fills, the file is done: no second pass, no double disk space.
• Resume via sidecar. A small <file>.evoftp-part record sits next to the download. Cancel, come back tomorrow, download the same file into the same folder and it continues; the sidecar disappears on completion. Never a folder of orphaned segments.
• Visible, lower threshold. Segmenting starts at 8 MB, not 100 MB, and the count is in the open: 4 per file by default, 8 on the Long distance profile, or a per-download override. Cyberduck does not document its segment count.
• Connection file. The client area builds a .evoftp file with host, port, username and password in it. Double-click and you are connected.
• Lighter, and on Linux. One window, one Download button; a single portable .exe on Windows, an AppImage on Linux, which Cyberduck’s desktop app does not offer.
• Tuned for distance. In our tests a Mac in India at 250–700 ms went from about 2.4 MB/s on one connection to line speed with the 16 MB window and 8 segments. Your line decides; we do not promise speeds.

If you use a seedbox

If your seedbox is one of several servers you touch — a NAS over SMB, a cloud bucket, a web host over FTP — Cyberduck covers all of them, and its default segmenting already puts it ahead of FileZilla on large files. Raise the connection cap, set the existing-file action to Compare, and live with the merge.

If the seedbox is the only thing you connect to, and you connect to pull large files home, evoftp does that one job with less friction: no merge, no segment folders, a connection file instead of a bookmark. It does nothing else — you give up sync, remote edit, cloud storage, throttling and signed builds. Keeping both is fine.

How to switch in two steps

1. Get the connection file. In the client area, open your service, find the Desktop app row and click Connection file; it is built in your browser from your current details, so it is never stale. Download evoftp from neo.myseedbox.site/share/evoftp and double-click the .evoftp file.
2. Add any other server by hand. There is no importer, but a connection is five fields: host, port 22, username, password, path. Leave Cyberduck installed; the two do not interfere.

FAQ

Does Cyberduck segment downloads by default?

Yes. Segmented download with multiple connections for file under Preferences → Transfers is on by default and applies to files over 100 MB on every protocol, SFTP included. After all segments arrive, Cyberduck merges them into the final file — the step this page calls the catch.

Why is my Cyberduck download stuck at 100%?

Almost certainly the merge. Cyberduck warns it “may take a considerable amount of time”, and on a large file it is effectively a full local copy. Wait it out and keep free space for roughly twice the file size. If the transfer failed before the merge, use Resume on the row in the Transfers window.

Is Cyberduck really free?

The download from cyberduck.io is GPL free software. It shows a donation prompt after installing and after updates; a contribution of at least 10 USD gives a registration key that removes it. The Mac App Store version costs $23.99 with no prompt.

Can I run Cyberduck and evoftp on the same seedbox at once?

Yes. Both are plain SFTP clients on port 22, each with its own connections. Just watch the total: Cyberduck at a high connection cap plus evoftp on the Long distance profile will saturate your own line long before the server notices.

Download evoftp

If the merge step has bitten you, try evoftp: free, open source, segmented by default for every file, connected in one click from your client area. The evoftp guide covers installation on all three platforms, the transfer profiles, and what can go wrong. Builds: neo.myseedbox.site/share/evoftp.