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$ /usr/sbin/sshd -f testconfig -p 22025 -d

debug1: sshd version OpenSSH_5.2p1
debug1: private host key: #0 type 0 RSA1
debug1: read PEM private key done: type RSA
debug1: private host key: #1 type 1 RSA
debug1: read PEM private key done: type DSA
debug1: private host key: #2 type 2 DSA
debug1: setgroups() failed: Operation not permitted
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-f'
debug1: rexec_argv[2]='testconfig'
debug1: rexec_argv[3]='-p'
debug1: rexec_argv[4]='22025'
debug1: rexec_argv[5]='-d'
debug1: Bind to port 22025 on
Server listening on port 22025.
Generating 1024 bit RSA key.
RSA key generation complete.
debug1: fd 4 clearing O_NONBLOCK
debug1: Server will not fork when running in debugging mode.
debug1: rexec start in 4 out 4 newsock 4 pipe -1 sock 7
debug1: inetd sockets after dupping: 3, 3
Connection from port 58477
debug1: Client protocol version 2.0; client software version OpenSSH_5.5
debug1: match: OpenSSH_5.5 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.2
debug1: privsep_preauth: successfully loaded Seatbelt profile for unprivileged child
debug1: list_hostkey_types: 
No supported key exchange algorithms
debug1: do_cleanup
debug1: do_cleanup
debug1: audit_event: unhandled event 12


$ ssh dgl@ -p 22025 -i ./ -v
OpenSSH_5.5p1, OpenSSL 0.9.8o 01 Jun 2010
debug1: Reading configuration data /Users/dgl/.ssh/config
debug1: Reading configuration data /opt/local/etc/ssh/ssh_config
debug1: Connecting to [] port 22025.
debug1: Connection established.
debug1: identity file ./ type 1
debug1: identity file ./ type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.2
debug1: match: OpenSSH_5.2 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.5
debug1: SSH2_MSG_KEXINIT sent
Connection closed by


Protocol 1,2
HostKey ./ssh_host_key
HostKey ./ssh_host_rsa_key
HostKey ./ssh_host_dsa_key
RSAAuthentication yes
PubkeyAuthentication yes
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does this error happen with a plain-vanilla sshd_config? – warren Jul 7 '10 at 13:17
What is the contant of testconfig? Hostkey and such do not belong into ssh_config. – ott-- Oct 11 '11 at 17:48
up vote 3 down vote accepted

I just hit the same issue, solved it by turning my relative HostKey path into an absolute one, i.e. instead of

HostKey ./ssh_host_key


HostKey /home/dmitry/ssh_host_key

or wherever it is.

That error isn't very helpful is it?

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I ran into this problem on Fedora. Eventually I noticed:

root@wisdom:/etc/ssh# ll
total 268K
drwxr-xr-x.   2 root root     4.0K Jun 30 06:06 ./
drwxr-xr-x. 128 root root      12K Jun 30 05:15 ../
-rw-r--r--.   1 root root     237K Jun  8 23:30 moduli
-rw-r--r--.   1 root root     2.2K Jun  8 23:30 ssh_config
-rw-------.   1 root root     4.3K Jun 30 06:03 sshd_config
-rw-r-----.   1 root ssh_keys    0 Jun 27 00:46 ssh_host_ecdsa_key
-rw-r--r--.   1 root root        0 Jun 27 00:46
-rw-r-----.   1 root ssh_keys    0 Jun 27 00:46 ssh_host_ed25519_key
-rw-r--r--.   1 root root        0 Jun 27 00:46
-rw-r-----.   1 root ssh_keys    0 Jun 27 00:46 ssh_host_rsa_key
-rw-r--r--.   1 root root        0 Jun 27 00:46

The key files are zero length! I generated new key pairs and it fixed the problem:

ssh-keygen -t rsa -f /etc/ssh/ssh_host_rsa_key
ssh-keygen -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key
ssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key
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Thanks, this worked for me. I experienced the same on a CentOS 7.1 minimal installation. – Torsten Aug 7 '15 at 17:34
Got exactly the same thing on a minimal Fedora 22 installation. Thanks for the hint. – Lefteris Jan 19 at 22:08

FWIW, I just ran into the same error message, but with a different cause. In my case the problem turned out to be that my host private key files were mode 640 instead of 600. A quick chmod and sshd restart solved the problem. I guess the common theme here is sshd not loading the host keys for one reason or another.

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I've just had this issue hacking around with cloud-init. In my case, the cause was that the host keys had not been generated, and dpkg-reconfigure openssh-server (Debian/Ubuntu -specific) fixed it.

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I ran into this error message and solved it by setting:

UsePAM yes

It only happened with passwordless accounts (like root).

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I actually ran into this problem...and it was our good old friend SELinux.

Running setenforce 0 proves that it worked but this isn't a good solution. However, as soon as that helped to make the ultimate solution more clear.

$ cd /etc/ssh
$ restorecon -Rv *

Re-enabling SELinux (setenforce 1) ... and all is well.

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