If you are running in k8s and the process stops after authentication with the CPU reaching 100%, add this line to your k8s yaml.

[canweed]

command: ["/bin/sh", "-c", "ulimit -n 65535 && exec /entrypoint"]

[Thorndike]

Nice! Before that I could not log in to the sftp server due to timeouts

[dmbonsall]

command: ["/bin/sh", "-c", "ulimit -n 65535 && exec /entrypoint"]

@canweed, thanks for this fix! I had the exact same problem of the process hanging in Kubernetes with the CPU stuck at 100% right after authentication. Do you happen to know why this is a problem in Kubernetes only? I have no issue running in docker-on-mac as a standalone container, and was even able to run this with no issues for several weeks on a real Kubernetes cluster until it started hanging sometime last week. Is this something that could be fixed in the image?

[canweed]

command: ["/bin/sh", "-c", "ulimit -n 65535 && exec /entrypoint"]

@canweed, thanks for this fix! I had the exact same problem of the process hanging in Kubernetes with the CPU stuck at 100% right after authentication. Do you happen to know why this is a problem in Kubernetes only? I have no issue running in docker-on-mac as a standalone container, and was even able to run this with no issues for several weeks on a real Kubernetes cluster until it started hanging sometime last week. Is this something that could be fixed in the image?

I want to clarify first that atmoz/sftp is not at fault. I also looked into atmoz/sftp and what it does is simply start from "FROM debian:bullseye" or "FROM alpine:latest," then install openssh-server, and configure sshd_config with a shell script.

The problem occurs in the following situation:
After entering the terminal, when you execute the command ulimit -n, it returns:

ulimit -n
1073741816

This very large value seems to be the issue.

This is a problem not only in Kubernetes but also in Docker on Rocky Linux 9.2. In Docker, the issue can be resolved by setting the option --ulimit nofile=65536:65536. However, since there is no way to set this option in Kubernetes, the

command ["/bin/sh", "-c", "ulimit -n 65535 && exec /entrypoint"]

is used to intercept the entrypoint and arbitrarily run ulimit -n 65535.

Therefore, resolving this in the image is straightforward. You just need to copy the original entrypoint from:
https://github.com/atmoz/sftp/blob/master/files/entrypoint
Add ulimit -n 65535 at the top of this script, and use it in your Dockerfile.