我重启了 Fedora 25 服务器，因为已经 3 天没重启了（我只安装了 JRE 和 screen），然后发现 SSH 停止工作了。有时连接被重置，有时连接被关闭。
sh-3.2# ssh [email protected]
Connection reset by 192.168.1.127
我不知道如何查看我的日志，因为现在我不再具有 ssh 访问权限，但是如果我使用 ssh -vvv 则会输出以下内容（我不确定 OS X El Capitan 的输出是否与 Linux 一样多）
sh-3.2# ssh -vvv [email protected]
OpenSSH_6.9p1, LibreSSL 2.1.8
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug1: /etc/ssh/ssh_config line 56: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to 192.168.1.127 [192.168.1.127] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.9
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 192.168.1.127:22 as 'root'
debug3: hostkeys_foreach: reading file "/var/root/.ssh/known_hosts"
debug1: SSH2_MSG_KEXINIT sent
Connection reset by 192.168.1.127
sh-3.2#
我通常使用公钥进行连接，但使用公钥不会改变上面的输出。Nginx 仍与 Cockpit 一起完美运行，网络方面没有任何变化。如果我尝试通过 SSH 将我的服务器连接到自身，则不会再发生任何变化。（我知道始终使用 root 是不安全的，但我已经尝试了其他所有方法）
[root@localhost ~]# ssh -vvvv localhost
OpenSSH_7.4p1, OpenSSL 1.0.2k-fips 26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug3: /etc/ssh/ssh_config line 56: Including file /etc/ssh/ssh_config.d/05-red
hat.conf depth 0
debug1: Reading configuration data /etc/ssh/ssh_config.d/05-redhat.conf
debug1: /etc/ssh/ssh_config.d/05-redhat.conf line 2: include /etc/crypto-policie
s/back-ends/openssh.config matched no files
debug1: /etc/ssh/ssh_config.d/05-redhat.conf line 8: Applying options for *
debug2: resolving "localhost" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to localhost [::1] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to localhost:22 as 'root'
debug3: hostkeys_foreach: reading file "/root/.ssh/known_hosts"
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
Connection reset by ::1 port 22
[root@localhost ~]# ^C
此外，我的网络上的其他设备都无法连接。我没有尝试过 PuTTY，但 Cyberduck 只是告诉我“接收失败”。我注意到，在发送“SSH2_MSG_KEXINIT”后，连接总是会重置，但我不知道它是什么。
这也是我的 ssh 配置，所有这些都被注释掉了：
[root@localhost ~]# cat /etc/ssh/ssh_config
# $OpenBSD: ssh_config,v 1.30 2016/02/20 23:06:23 sobrado Exp $
# Host *
# ForwardAgent no
# ForwardX11 no
# RhostsRSAAuthentication no
# ConnectTimeout 0
# StrictHostKeyChecking ask
# IdentityFile ~/.ssh/identity
# IdentityFile ~/.ssh/id_rsa
# IdentityFile ~/.ssh/id_dsa
# IdentityFile ~/.ssh/id_ecdsa
# IdentityFile ~/.ssh/id_ed25519
# Port 22
# Protocol 2
# Cipher 3des
# Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3d
es-cbc
# MACs hmac-md5,hmac-sha1,[email protected],hmac-ripemd160
# EscapeChar ~
# Tunnel no
# TunnelDevice any:any
# PermitLocalCommand no
# VisualHostKey no
# ProxyCommand ssh -q -W %h:%p gateway.example.com
# RekeyLimit 1G 1h
#
# To modify the system-wide ssh configuration, create a *.conf file under
# /etc/ssh/ssh_config.d/ which will be automatically included below
Include /etc/ssh/ssh_config.d/*.conf
我尝试过 dnf reinstall openssh-server，但什么都没改变。我不确定任何事情，但正如我所说，我不确定如何在 Fedora 25 中查看 OpenSSH 的日志文件（完全不知道？我说的它有日志对吗？）。如果可以修复这个问题就好了，因为它让我 4 个小时无法工作。谢谢。
答案1
为了可见性，关联@Jakuje 的评论帮我解决了这个问题。
将 MTU 大小重置为 576：
ifconfig eth0 mtu 576
仅在运行 ssh 服务器的主机上执行此操作对我来说是可行的，但链接建议在服务器和客户端上都执行此操作。
答案2
好吧。所以，通过 重新启动 sshdsystemctl restart sshd不起作用。但是，有人建议我使用它# /sbin/sshd来启动 OpenSSH。令人惊讶的是，它起作用了，并且一切都像重新启动之前一样正常。我不明白为什么。可能是权限问题。我不确定，但“对等方重置连接”错误似乎是最难调试的错误之一。