When starting sshd, 'Could not load host key' error is reported

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When starting sshd, 'Could not load host key' error is reported_PHP tutorial

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Jul 12, 2016 am 08:51 AM

android

When starting sshd, the "Could not load host key" error is reported

Phenomenon: When starting the sshd service, although the service seems to be started successfully, the client cannot connect to the sshd server.
As follows:

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>[root@aefe8007a17d ~]# /usr/sbin/sshd<br /></li><li>Could not load host key: /etc/ssh/ssh_host_rsa_key<br /></li><li>Could not load host key: /etc/ssh/ssh_host_ecdsa_key<br /></li><li>Could not load host key: /etc/ssh/ssh_host_ed25519_key</li></ol>

Cause:
1. From the prompt message, it seems that the sshd daemon cannot load the host key file because these key files cannot be found (configuration file /etc/ The key file name and path have been defined in ssh/sshd_config);
2. Generally, after the openssh service is installed normally, the host will automatically generate the corresponding host key file, but this step was not completed due to unknown reasons, resulting in Unable to connect via ssh remotely.

Check whether the key file exists (there is another phenomenon: the key file exists, but the file size is 0):

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>[root@aefe8007a17d ~]# ll /etc/ssh/<br /></li><li>total 252<br /></li><li>-rw-r--r-- 1 root root 242153 Mar 21 22:18 moduli<br /></li><li>-rw-r--r-- 1 root root   2208 Mar 21 22:18 ssh_config<br /></li><li>-rw------- 1 root root   4361 Mar 21 22:18 sshd_config</li></ol>

Regenerate the host key file:
1. Generate rsa_key (-t indicates the encryption type used by the generated key; -f item is followed by the key file name to be generated);

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>[root@aefe8007a17d ~]# ssh-keygen -t rsa -f /etc/ssh/ssh_host_rsa_key<br /></li><li>Generating public/private rsa key pair.<br /></li><li>Enter passphrase (empty for no passphrase): <br /></li><li>Enter same passphrase again: <br /></li><li>Your identification has been saved in /etc/ssh/ssh_host_rsa_key.<br /></li><li>Your public key has been saved in /etc/ssh/ssh_host_rsa_key.pub.<br /></li><li>The key fingerprint is:<br /></li><li>5e:2d:19:51:b1:e3:e0:60:65:53:e4:14:f8:d8:38:af root@aefe8007a17d<br /></li><li>The key's randomart image is:<br /></li><li>+--[ RSA 2048]----+<br /></li><li>|          ==Bo   |<br /></li><li>|         o.= .   |<br /></li><li>|        o o=+    |<br /></li><li>|       . o+*o.   |<br /></li><li>|        S =oo    |<br /></li><li>|       . . ..    |<br /></li><li>|        .  .     |<br /></li><li>|          E      |<br /></li><li>|                 |<br /></li><li>+-----------------+<br /></li><li>[root@aefe8007a17d ~]# ssh-keygen -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key</li><li><br /></li></ol>

2. Generate ecdsa_key;

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>[root@aefe8007a17d ~]# ssh-keygen -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key</li></ol>

3 . Generate ed25519_key.

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>[root@aefe8007a17d ~]# ssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key</li></ol>

Check again whether the key file exists and is compliant. You can see that the corresponding host key file has been generated (actually the host key file is the private key and the .pub file is the public key):

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>[root@aefe8007a17d ~]# ll /etc/ssh/<br /></li><li>total 276<br /></li><li>-rw-r--r-- 1 root root 242153 Mar 21 22:18 moduli<br /></li><li>-rw-r--r-- 1 root root   2208 Mar 21 22:18 ssh_config<br /></li><li>-rw------- 1 root root    227 May 22 16:48 ssh_host_ecdsa_key<br /></li><li>-rw-r--r-- 1 root root    179 May 22 16:48 ssh_host_ecdsa_key.pub<br /></li><li>-rw------- 1 root root    411 May 22 16:48 ssh_host_ed25519_key<br /></li><li>-rw-r--r-- 1 root root     99 May 22 16:48 ssh_host_ed25519_key.pub<br /></li><li>-rw------- 1 root root   1679 May 22 16:48 ssh_host_rsa_key<br /></li><li>-rw-r--r-- 1 root root    399 May 22 16:48 ssh_host_rsa_key.pub<br /></li><li>-rw------- 1 root root   4361 Mar 21 22:18 sshd_config</li></ol>

At this time, the client can ssh to connect to the sshd server:

<ol style="margin:0 1px 0 0px;padding-left:40px;" start="1" class="dp-css"><li>[root@localhost ~]# ssh 172.17.0.2<br /></li><li>The authenticity of host '172.17.0.2 (172.17.0.2)'can't be established.<br />ECDSA key fingerprint is 37:2a:69:46:c4:bd:92:b2:43:b4:cc:42:41:8e:12:2e.<br />Are you sure you want to continue connecting (yes/no)?</li></ol>

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