sshd_config - make 'Port' config key overridable using an env var

Dockerfile

@@ -1,6 +1,8 @@
 FROM debian:bullseye
 MAINTAINER Adrian Dvergsdal [atmoz.net]
 
+ENV SSHD_PORT 22
+
 # Steps done in one RUN layer:
 # - Install packages
 # - OpenSSH needs /var/run/sshd to run
@@ -15,6 +17,4 @@ COPY files/sshd_config /etc/ssh/sshd_config
 COPY files/create-sftp-user /usr/local/bin/
 COPY files/entrypoint /
 
-EXPOSE 22
-
 ENTRYPOINT ["/entrypoint"]

README.md

@@ -30,6 +30,8 @@ Easy to use SFTP ([SSH File Transfer Protocol](https://en.wikipedia.org/wiki/SSH
     own home directory, so make sure there are at least one subdirectory if you
     want them to upload files.
   - For consistent server fingerprint, mount your own host keys (i.e. `/etc/ssh/ssh_host_*`)
+- Override port
+  - The container will internally listen on the port 22 (default port for sshd), but if for any reasons you want another port to be used internally instead of the default, you can change it with the env var SSHD_PORT
 
 # Examples
 
@@ -64,6 +66,12 @@ sftp:
     command: foo:pass:1001
 ```
 
+### Overriding the default port, so that sshd doesn't listen port 22
+
+```
+docker run -e SSHD_PORT=1234 -p 1234:1234 -d atmoz/sftp foo:pass:::upload
+```
+
 ### Logging in
 
 The OpenSSH server runs by default on port 22, and in this example, we are forwarding the container's port 22 to the host's port 2222. To log in with the OpenSSH client, run: `sftp -P 2222 foo@<host-ip>`

files/entrypoint

@@ -90,6 +90,9 @@ if [ -d /etc/sftp.d ]; then
     unset f
 fi
 
+
+sed -i "s/SSHD_PORT/$SSHD_PORT/" /etc/ssh/sshd_config
+
 if $startSshd; then
     log "Executing sshd"
     exec /usr/sbin/sshd -D -e

files/sshd_config

@@ -20,3 +20,5 @@ ChrootDirectory %h
 
 # Enable this for more logs
 #LogLevel VERBOSE
+
+Port SSHD_PORT