Duplicating failing when using sudo on login :: Support Forum

immewnity
Joined:: 2026-07-31
Posts:: 3
Location:: Chicago, IL

Duplicating failing when using sudo on login

2026-07-31 06:35

I've got an SFTP site set up as per the "Use sudo on Login" section of https://winscp.net/eng/docs/faq_su:

SFTP->SFTP server is set to sudo /usr/lib/openssh/sftp-server
myusername ALL=NOPASSWD: /usr/lib/openssh/sftp-server is set in sudoers
Additionally, authentication is via password-protected SSH key.

This works perfectly fine for most file operations; I can edit/delete/move files without issue. However, when I try and duplicate files (https://winscp.net/eng/docs/ui_duplicate), I get an error with exit status 1:

Error skipping startup message. Your shell is probably incompatible with the application (BASH is recommended).

Duplicating via local temporary copy works fine.

Am I missing something, or is this expected?

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martin◆ Site Admin
Joined:: 2002-12-10
Posts:: 43,017
Location:: Prague, Czechia

Re: Duplicating failing when using sudo on login

2026-07-31

Your SFTP server does not support direct duplication, so WinSCP needs to fallback to using shell commands. For that you need to configure the sudo for the shell too:
https://winscp.net/eng/docs/ui_login_scp
https://winscp.net/eng/docs/faq_su

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immewnity
Joined:: 2026-07-31
Posts:: 3
Location:: Chicago, IL

2026-07-31 15:55

The SFTP server does appear to support direct duplication, though:

sftp> ls *.txt
test.txt
sftp> cp test.txt test2.txt
sftp> ls
test.txt    test2.txt

(running OpenSSH_10.0p2 Debian-7+deb13u4 for context)

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martin◆ Site Admin
Joined:: 2002-12-10
Posts:: 43,017
Location:: Prague, Czechia

Re: Duplicating failing when using sudo on login

2026-07-31

Please attach a full session log file showing the problem (using the latest version of WinSCP).

To generate the session log file, enable logging, log in to your server and do the operation and only the operation that causes the error. Submit the log with your post as an attachment. Note that passwords and passphrases not stored in the log. You may want to remove other data you consider sensitive though, such as host names, IP addresses, account names or file names (unless they are relevant to the problem). If you do not want to post the log publicly, you can mark the attachment as private.

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immewnity

2026-07-31 16:26

Well, uh, it's working now - ever since running the cp command above to test copying directly in the SFTP client, I'm able to duplicate without issue. Weird!

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Duplicating failing when using sudo on login