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Ubuntu 16.04 LTS sshd 重启问题

tag-icon • tag-icon 16.04 server ssh sshd
Ubuntu 16.04 LTS sshd 重启问题

我选择 Ubuntu 16.04 LTS 作为生产服务器的主要操作系统。它拥有最新版本的 Linux 内核，更新频繁，而且似乎很稳定。

然而两天来我都无法解决 sshd 服务的问题。总体来说，它运行良好。问题在系统重启后出现。我可以通过 SSH 登录，但 systemd 说 sshd.service 没有运行/无法启动。此外，我无法重新启动 sshd 服务，并且看到相同的错误。

● ssh.service - OpenBSD Secure Shell server
   Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Sat 2017-03-11 12:17:42 UTC; 37s ago
  Process: 3535 ExecStart=/usr/sbin/sshd -D $SSHD_OPTS (code=exited, status=255)
 Main PID: 3535 (code=exited, status=255)

Mar 11 12:17:42 node2 systemd[1]: Starting OpenBSD Secure Shell server...
Mar 11 12:17:42 node2 sshd[3535]: error: Bind to port 22 on 0.0.0.0 failed: Address already in use.
Mar 11 12:17:42 node2 sshd[3535]: fatal: Cannot bind any address.
Mar 11 12:17:42 node2 systemd[1]: ssh.service: Main process exited, code=exited, status=255/n/a
Mar 11 12:17:42 node2 systemd[1]: Failed to start OpenBSD Secure Shell server.
Mar 11 12:17:42 node2 systemd[1]: ssh.service: Unit entered failed state.
Mar 11 12:17:42 node2 systemd[1]: ssh.service: Failed with result 'exit-code'.

我多次在服务器上重新安装了 Ubuntu 16.04 LTS，并尝试更改 sshd_config 文件来修复此问题。但是这无济于事。这是我的 sshd_config：

# Package generated configuration file
# See the sshd_config(5) manpage for details

# What ports, IPs and protocols we listen for
Port 22
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
ListenAddress 0.0.0.0
Protocol 2

# HostKeys for protocol version 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes

# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 1024

# Logging
SyslogFacility AUTH
LogLevel INFO

# Authentication:
LoginGraceTime 120
PermitRootLogin no
StrictModes yes

RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile     %h/.ssh/authorized_keys

# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes

# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no

# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no

# Change to no to disable tunnelled clear text passwords
PasswordAuthentication yes

# Kerberos options
#KerberosAuthentication no
#KerberosGetAFSToken no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes

X11Forwarding yes
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
#UseLogin no

#MaxStartups 10:30:60
#Banner /etc/issue.net

# Allow client to pass locale environment variables
AcceptEnv LANG LC_*

Subsystem sftp /usr/lib/openssh/sftp-server

# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes
UseDNS no
GSSAPIAuthentication no

我从监控系统收到了很多关于此问题的消息。我只是想确保一切正常，并且我的服务器将来不会出现问题。

有人可以帮忙吗？

谢谢

答案1

Mar 11 12:17:42 node2 sshd[3535]: error: Bind to port 22 on 0.0.0.0 failed: Address already in use.
Mar 11 12:17:42 node2 sshd[3535]: fatal: Cannot bind any address.
Mar 11 12:17:42 node2 systemd[1]: ssh.service: Main process exited, code=exited, status=255/n/a

该sshd进程正在运行，您可以连接到服务器，但systemd对此并不知情（他不知道在启动新sshd进程之前要终止哪个进程）。假设这是sshd手动启动时发生的，或者以某种方式systemd丢失了进程的踪迹sshd，您应该能够通过以下步骤解决它：

  • 找到主sshd进程并终止它。不要终止子进程（也称为sshd），否则您将从服务器中断开连接！

    $ ps axf | grep sshd
 2208 ?        Ss     0:00 /usr/sbin/sshd
18812 ?        Ss     0:00  \_ sshd: pi [priv]  
18891 ?        S      0:01      \_ sshd: pi@pts/0   
19123 pts/0    S+     0:00              \_ grep --color=auto sshd
# kill -9 2208

  • 启动sshd服务：

    systemctl start sshd

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