Hot answers tagged

48 votes
Accepted

Ubuntu 22.04 SSH the RSA key isn't working since upgrading from 20.04

Cause The RSA SHA-1 hash algorithm is being quickly deprecated across operating systems and SSH clients because of various security vulnerabilities, with many of these technologies now outright ...
  • 29.7k
23 votes
Accepted

SSH without password does not work after upgrading from 18.04 to 22.04

The RSA SHA-1 hash algorithm is being quickly deprecated. There is a workaround for re-enabling RSA at SSH-RSA key rejected with message "no mutual signature algorithm" . Add the following ...
  • 106k
21 votes
Accepted

How can I perform a secure automatic file transfer between two servers?

You can't hide anything on the system from someone who have root access. Even you are using encrypted home directory while you are logged-in it is decrypted and the root user can access the data. ...
  • 28.8k
13 votes

Ubuntu 22.04 SSH the RSA key isn't working since upgrading from 20.04

When I need to re-enable a deprecated method in order to connect to a server I can't upgrade (e.g. an embedded legacy device such as an old router) I rather like doing this on a per-device basis ...
  • 1,664
13 votes
Accepted

SSH default port not changing (Ubuntu 22.10)

SSHd now uses socket-based activation Ubuntu 22.10 or later. Read more about this change being discussed here. TLDR: The /etc/ssh/sshd_config are unused, now that I read the comments in full I found: ...
  • 233
10 votes

ssh: challengeresponseauthentication in 22.04 Ubuntu

Seems like the ChallengeResponseAuthentication option was replaced by KbdInteractiveAuthentication in /etc/ssh/sshd_config. I just enabled 2FA with pam_google_authenticator.so as described in the ...
  • 318
10 votes
Accepted

For new AWS instance, "Using username "ubuntu". Server refused our key."

Try updating putty to the latest version i was using an older version updated it to 0.76 and it worked flawlessly https://www.chiark.greenend.org.uk/~sgtatham/putty/ hope this helps Eric adds: For ...
8 votes
Accepted

scp: How to change ownership of folder and files while transferring files

scp doesn't have an option for changing ownership on-the-fly but, rsync does ... it has -og --chown=user:group ... So, you can do something like: rsync -og --chown=srv2 /var/www/vhosts/srv1.com/...
  • 18.4k
6 votes
Accepted

ssh known_hosts file not using hostnames anymore

As others have commented, HashKnownHosts yes is causing the hostname to not autocomplete due to it being hashed. Add that to a "global" section by using Host * to match all hosts. Host * ...
6 votes

How can I perform a secure automatic file transfer between two servers?

Use rsync in a cronjob, as usual. On the rsync client, users with "sudo" privilege will be able to see the username and password needed to access the specific folders shared by the rsync ...
  • 4,762
6 votes
Accepted

Block all incoming requests but local network

I would suggest you adjust your approach from single-port-focus to a full 'defense' posture: Whitelist IPs, reject all other connection attempts. This applies for most all ports on your environment - ...
  • 70.3k
5 votes

SSH without password does not work after upgrading from 18.04 to 22.04

You can add the following line to /etc/ssh/ssh_config if you want the add this config for all users or to ~/.ssh/config if you want to add this to your own user. HostKeyAlgorithms +ssh-rsa
  • 51
5 votes
Accepted

Increase security for ssh login via public / private key: use port forwarding in router or in server?

It (mostly) does not matter If you just want to reduce the number of login attempts in the server's system log, either approach is fine. To be specific here are the two approaches: You can have the ...
  • 29.7k
5 votes

php 7.4, ssh_connect(), "Unable to exchange encryption keys" only when connecting to ubuntu 22.04 machines

AH HA!!!!!! I found the solution. The issue is the key exchange process of "ssh-rsa" is not accepted on Ubuntu 22.04 systems. I switched to using "ecdsa-sha2-nistp256" and it works!...
  • 821
5 votes

stderr: No ECDSA host key is known for github.com and you have requested strict checking

... and you have requested strict checking. You can check the Jenkins/Git-Host-Key-Verification setting under Global Security... Obviously you can workaround it by selecting No verification which is ...
  • 151
4 votes
Accepted

How to copy files from an ssh machine to my local pc?

Basic sftp tutorial Use the command: sftp username@institution This will take you to the sftp prompt like: Connected to institution. sftp> Now type help like this: sftp> help This will show ...
  • 29.7k
4 votes

How can I perform a secure automatic file transfer between two servers?

Just send the file to serverA instead of having a user on serverA copy it from serverB. If you want to copy foo.txt from serverB to serverA, you can do it in two basic ways: Run a command on serverA ...
  • 96.1k
4 votes
Accepted

How effective is Deja Dup backups?

No, 1st off: permission are likely skewered: you need to probably make sure user id, and group id are identical. Also: it is not the intended usage for deja-dup. Clonezilla is not a backup tool and as ...
  • 287k
4 votes

Putty 0.76 does not work on Ubuntu 22.04 unless with Sudo

It seems the default font for PuTTY 0.76 in Ubuntu 22.04 is "Server:Fixed". Not sure what that is, but I browsed the available fonts in PuTTY, and chose one to my liking. Now PuTTY is ...
  • 191
4 votes
Accepted

Ubuntu 22.04 problem with ssh

Since I can't comment, I'll put it as an answer. I had the same problem, after hours of searching found something that fixed it. I added IPQoS none To my /etc/ssh/ssh_config Looks like something ...
4 votes

SSH Error : bash: ./installer: cannot execute binary file: Exec format error

The problem is your system is an Arm64 platform, and the executable you're trying to run is an Intel64. Those are two different hardware architectures, that require different binaries to run. You can ...
4 votes
Accepted

Unable to disable password authentication over SSH

I already resolved this issue. Inside the directory /etc/ssh/sshd_config.d/ there is only one .conf file (50-cloud-init.conf), but inside it contains the line: PasswordAuthentication yes I changed the ...
3 votes

ssh refusing connection with message "no hostkey alg"

I was having the same problem connecting older clients to a Slackware 15 server. This thread is the top result for ssh "no hostkey alg" but the existing answers did not solve my problem, so ...
  • 131
3 votes

Upgraded Ubuntu, now password to get into server will not work

That is the very picture of a successful login, complete with shell prompt awaiting your command. Advice: The question suggests that you might be a very new user. I advise against using the root ...
  • 51.7k
3 votes

WSL Nano scrolling up to see terminal

Short summary: I can reproduce your desired behavior in Ubuntu/WSL using Windows Terminal I can reproduce the behavior that you don't like in Ubuntu/WSL using the legacy Windows Console Host More ...
  • 11.6k
3 votes

How effective is Deja Dup backups?

Not for System-wide Backup DejaDup is not the tool for system-wide backups. Backing up apps and system folders in Linux is tricky as one needs to preserve the ownership and permissions to make the ...
  • 29.7k
3 votes
Accepted

On Ubuntu, a simple script with a disabling function didn't work

My guess is the script isn't run with Bash. The shebang (first line of your script) is wrong. This should be: #!/bin/bash Then your if-statement is using [[, which is a "Bashism" - so I ...
3 votes

SSH without password does not work after upgrading from 18.04 to 22.04

Update: I suggest trying the command-line lower down to see if the configuration changes proposed will actually work, that way you'll only be making config changes if you've already checked that they'...
3 votes

Recent update for SSH breaks backward compatibility, how do I downgrade to the previous version?

I had a problem connecting to older devices, and I made it work in Ubuntu 22.04 with OpenSSH 8.9 / OpenSSL 3.0.2 by adding the following lines in the Host section of /etc/ssh/ssh_config on the client ...
3 votes
Accepted

Using scp to copy a remote file containing spaces requires double space escaping. Why?

You can enable printing command traces before executing a command with set -x to see what is actually being passed to scp in the three cases like so: ubuntu@ubuntu:~/test$ mkdir 'folder 1' ubuntu@...
  • 18.4k

Only top scored, non community-wiki answers of a minimum length are eligible