The Tool Desk
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To connect from Ubuntu 16.04 or 18.04 to a remote SFTP server, install the OpenSSH client: sudo apt update && sudo apt install openssh-client. For a graphical, drag-and-drop app, install FileZilla and select SFTP – SSH File Transfer Protocol when configuring the connection. Both Ubuntu releases are past standard security support, so treat these steps as legacy-system guidance and plan an upgrade where possible.
Choose the client that fits your task
| Option | Best for | What to know |
|---|---|---|
OpenSSH sftp |
Terminal use, servers without a desktop, and scripted or lightweight transfers | Installed by the openssh-client package; no graphical interface. |
| FileZilla | Browsing folders visually, drag-and-drop transfers, and saved site profiles | Choose SFTP explicitly; FileZilla also supports FTP and FTPS. Ubuntu FileZilla manpage. |
| File-manager SFTP | Occasional transfers from a desktop file manager | Availability and menu labels depend on the desktop environment and installed components. A location may be entered as sftp://[email protected]. |
An SFTP client connects outward to a server. Installing openssh-client does not create an SFTP server or grant an account access. Do not install openssh-server unless you intend to accept SSH connections to this Ubuntu machine.
Install the OpenSSH SFTP client
- Check the release. Run
lsb_release -aorcat /etc/os-releaseand confirm the system is Xenial (16.04) or Bionic (18.04). - Refresh package information. Run
sudo apt update. It should finish without repository errors. - Install the client. Run
sudo apt install openssh-client. Ubuntu’s OpenSSH client package provides thesftpprogram; see Ubuntu’s OpenSSH documentation and the Bionic package listing. - Verify the installation. Run
command -v sftp; a typical result is/usr/bin/sftp. You can also check the package withdpkg -s openssh-clientor inspect its candidate version withapt-cache policy openssh-client.
The commands are the same on both releases when their package sources are working. The version available depends on the configured repositories and system state; do not assume a particular archived package version.
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Before connecting, obtain the server hostname or IP address, your username, the port (normally 22), and the password or private-key details from the server administrator. You also need network access and permission to use the remote directory. Installing a client does not create a remote account.
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For a standard connection, run:
sftp [email protected]
For a server configured on another port, use uppercase -P:
sftp -P 2222 [email protected]
For a private key, specify its path:
sftp -i ~/.ssh/id_ed25519 [email protected]
To start in a particular remote directory, append its path:
sftp [email protected]:/var/www
Whether that path is visible depends on the account’s permissions and any server-side restrictions. For example, a chrooted account may see a restricted directory as its root.
Check the host key before accepting it
On first connection, OpenSSH may show the server’s host-key fingerprint and ask whether to continue. Verify the fingerprint with the server administrator or another trusted channel before accepting it. OpenSSH records accepted keys in ~/.ssh/known_hosts. A warning about a changed key can indicate a legitimate server rebuild, but it can also signal an unexpected server change; do not bypass it without checking.
Use the interactive SFTP prompt
After authentication, the sftp> prompt accepts commands. cd and ls refer to the remote side; lcd and lls refer to your local side.
| Command | Purpose |
|---|---|
pwd / lpwd |
Show the remote / local working directory. |
ls / lls |
List remote / local files. |
cd directory / lcd directory |
Change the remote / local working directory. |
get file.txt |
Download a remote file to the local working directory. |
put file.txt |
Upload a local file to the remote working directory. |
get -r folder / put -r folder |
Download / upload a directory recursively. |
mkdir folder |
Create a remote directory, if permitted. |
rm file.txt |
Delete a remote file, if permitted. |
bye |
Disconnect. |
These commands are documented in the Ubuntu Bionic SFTP manpage. The manpage also documents the user@host[:path] and sftp:// forms; see the Ubuntu Focal SFTP manpage for the URI form.
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Install and configure FileZilla
For a graphical client, install the Ubuntu package:
sudo apt updatesudo apt install filezilla
Open FileZilla from the application menu by searching for “FileZilla,” or run filezilla in Terminal. In Site Manager, create a site and enter the server’s details. Exact labels can differ by FileZilla build.
- Protocol: SFTP – SSH File Transfer Protocol
- Host: server hostname or IP address
- Port: 22 unless the administrator supplied another port
- Logon type: Select the password or key-based option available in that build
- User: Your remote username; provide a password if requested
The local files appear on the left and remote files on the right. Drag files between the panes, then check the transfer queue and message log for errors. Do not select ordinary FTP when you intend to make an SSH-based SFTP connection, and do not dismiss security warnings simply to force a connection.
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Fix package installation problems on Ubuntu 16.04 or 18.04
“Unable to locate package”
First check network access, then run sudo apt update and inspect the output. A broken /etc/apt/sources.list, an incorrect release codename, or repositories that have moved can leave APT without usable package information. Do not add repositories for a different Ubuntu release.
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“404 Not Found” or “does not have a Release file”
Ubuntu 16.04 and 18.04 are old releases, and their package sources may no longer be available from ordinary mirrors. Ubuntu documents end-of-life release context at EOL; release-upgrade guidance is at Ubuntu Server release upgrades. If you must maintain the old system temporarily, use Ubuntu’s appropriate old-release archive guidance and preserve APT signature checks. Back up repository configuration before changing it. Do not use --allow-unauthenticated, disable signature verification, or install random downloaded packages as a shortcut.
Broken dependencies or an unavailable GUI build
FileZilla availability and compatibility depend on the repositories and package state on these legacy releases. Resolve APT source or dependency issues through official Ubuntu guidance rather than mixing packages from newer releases. If a secure, maintainable package path is unavailable, upgrade Ubuntu instead of weakening repository checks.
Troubleshoot connection and transfer errors
Test the network path
For a basic name/connectivity check, you can run ping -c 4 server.example.com, but a failed ping does not prove SFTP is unavailable because networks may block ICMP. A TCP check of the usual port is more relevant:
nc -vz server.example.com 22
If nc is missing, install it with sudo apt install netcat-openbsd. A timeout commonly points to routing, firewall, VPN, or hostname issues. “Connection refused” can mean the port is wrong, the remote SSH service is not listening, or a firewall is rejecting the connection.
Permission denied
Check that the username and authentication method are correct, that the server allows SFTP for the account, and that the account can access the requested directory. For a private key, confirm that you selected the correct file; OpenSSH commonly requires a private key to be readable only by its owner:
chmod 600 ~/.ssh/id_ed25519
This fixes only a local key-permission problem, not a wrong password, unauthorized account, or remote directory permission.
Host key verification failed
If the administrator confirms that the server was rebuilt or its host key changed, remove only that host’s stale entry with ssh-keygen -R server.example.com. Reconnect and verify the new fingerprint before accepting it. Do not delete the entire known_hosts file as a routine fix.
“Subsystem request failed on channel 0”
This usually points to server-side SFTP subsystem configuration or an account restriction. Installing another client on Ubuntu generally will not solve it; ask the server administrator to check the SSH service and account configuration.
Algorithm negotiation fails
An old Ubuntu client and a newer server may not share acceptable cryptographic algorithms. First prefer updating the operating system or correcting the server’s supported configuration. Enabling deprecated algorithms can reduce security; avoid global SSH changes, and use any narrow exception only with administrator guidance and a clear rollback.
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Collect more detail safely
Run sftp -vvv [email protected] to see more connection and authentication detail. Before sharing output, remove usernames, hostnames, IP addresses, and sensitive paths.
Alternatives for other transfer needs
One-off file copies with SCP
For a single upload, use scp file.txt [email protected]:/remote/path/. To download, use scp [email protected]:/remote/path/file.txt .. SFTP is more convenient for an interactive session and repeated browsing; SCP behavior has changed across OpenSSH versions, so it is not a complete substitute in every workflow.
Directory synchronization with rsync
For repeated synchronization, a common command is rsync -avz -e ssh ./local-folder/ [email protected]:/remote/folder/. This is aimed at mirroring changes, not visual browsing, and requires the remote side to permit the needed command execution.
Plan for the age of these Ubuntu releases
Ubuntu 16.04 standard security maintenance ended in April 2021; Ubuntu 18.04 standard security maintenance ended in May 2023. Canonical’s lifecycle information lists Ubuntu Pro/ESM coverage for 16.04 through April 2026 and 18.04 through April 2028, subject to applicable Ubuntu Pro terms and coverage: see Ubuntu ESM, the 18.04 release cycle, and the Ubuntu release list. As of September 2026, the listed 16.04 ESM end date has passed, while 18.04’s listed ESM period has not; neither is a good choice for a new deployment. Upgrade to a supported Ubuntu LTS release when possible. Old repositories, TLS certificates, application builds, or SSH algorithms may complicate use on these systems.
For machines that must remain on Ubuntu 18.04 temporarily, check current Ubuntu Pro eligibility and terms at Ubuntu Pro; extended maintenance is not a replacement for an upgrade plan.
Frequently Asked Questions
Is SFTP the same as FTP?
No. SFTP transfers files over SSH; FTP is a different protocol. In FileZilla, choose “SFTP – SSH File Transfer Protocol” for an SSH-based connection.
What port does SFTP use?
It normally uses TCP port 22, but the server administrator can configure another port.
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Can I use a private key file?
Yes. OpenSSH accepts a key path with sftp -i ~/.ssh/id_ed25519 [email protected]; FileZilla builds may offer a key-file logon option.
Can I use the Ubuntu file manager instead of FileZilla?
Some desktop environments support an SFTP location such as sftp://[email protected]. Availability and exact menus vary by Ubuntu desktop and installed components.
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