Ssh – Ubuntu 12.04 VPS SSH not running, how to reset SSH configuration files

sshubuntu-12.04

Yesterday after I re – enabled root user and rebooted the VPS, now SSH and SFTP are not running. FTP working. I can only connect this VPS via VPS provider web based console.

When I run "ssh restart" command in VPS provider console it shows "19 bad configuration option" in "ssh_config" file. But i didn't do anything like that. However that bad configuration option are similar to the default config file.

So how do i reset the ssh_config file without loosing anything? If i reinstall open SSH it will reset the ssh_config file to the default.

Best Answer

You will have to first uninstall openssh completely. You can do this by running

apt-get remove --purge openssh-server

then install and see if all works.

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SSH key stopped working on Ubuntu Azure VPS

I realize my mistake. Thanks @kasperd for helping me figure it out. I followed Azure's SSH creation instructions to the letter. When I generated my key, I used this command

openssl req -x509 -key ~/.ssh/id_rsa -nodes -days 365 -newkey rsa:2048 -out myCert.pem

which generates a new key that expires after 365 days. It just so happens that yesterday was that 365th day which means my key no longer works. Since that was the only key to the VM I guess I'm screwed? Kinda seems like it. Ugh.

Update: Per @kasperd 's comments, the fact that my server stopped letting me SSH in exactly a year after setting it up may just be a crazy coincidence. Thanks to a conversation via the discussion thread over on the Azure documentation site, I discovered that Azure Linux VMs created via the gallery are loaded with the Microsoft Azure Linux Agent which allows admins to reset SSH through the command line (i.e. Powershell). So while it's a pain for me to switch over to Windows, I was able to follow the steps and reset SSH options on my VM. Unfortunately, I still wasn't able to SSH into my machine. Obviously I did something drastic to my machine that wasn't covered by the reset options, but for users with less drastic cases hopefully they can follow some of these links to help their situation.

Ssh – How to disable sftp access to user with ssh already disabled (user shell = /bin/false, but connection still works with sftp)

I don't think that Match User is working in the way that you think it is.

Match
Introduces a conditional block. If all of the criteria on the Match line are satisfied, the keywords on the following lines override those set in the global section of the config file, until either another Match line or the end of the file. If a keyword appears in multiple Match blocks that are satisfied, only the first instance of the keyword is applied.

So in your particular case the Match User usersftp2 only applies to and overrides the configuration for usersftp2.

When your usersftp1 connects, the sftp program is run for them by sshd and no user specific configurations are applied.

If I understand your question correctly you should be able to do what you want with a group.

create a group e.g. sftpusers (groupadd...) and then add the users you want to allow to it (usermod -G ...)

Then configure sshd to only allow sftp for users in that group

Match Group sftpusers
  # Force the connection to use SFTP
  ForceCommand internal-sftp
  # Disable tunneling, authentication agent, TCP and X11 forwarding.
  PermitTunnel no
  AllowAgentForwarding no
  AllowTcpForwarding no
  X11Forwarding no

Best Answer

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SSH key stopped working on Ubuntu Azure VPS

Ssh – How to disable sftp access to user with ssh already disabled (user shell = /bin/false, but connection still works with sftp)

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