我希望这是发布此内容的正确地方。今天，我在重启后被锁定在了我的 ec2 之外。当我尝试 ssh 时，它显示的内容如下：
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 *
debug2: ssh_connect: needpriv 0
debug1: Connecting to xx.xx.xx.xx [xx.xx.xx.xx] port 22.
debug1: connect to address xx.xx.xx.xx port 22: Connection refused
ssh: connect to host xx.xx.xx.xx port 22: Connection refused
我已回答过以下问题：
https://stackoverflow.com/questions/14026148/running-ec2-instance-suddenly-refuses-ssh-connection
https://www.youtube.com/watch?v=_P29ZHu_feU
我已经尝试过分离卷以修复 sshd_config，但这似乎无法解决问题。幸运的是，今天做任何事情之前我都有 AMI，我重新启动了实例，它运行良好。但是，当我运行并yum update重新启动实例时，我又被锁定了。
这些是今天更新的内容：
Dependencies Resolved
================================================================================================================================================================
Package Arch Version Repository Size
================================================================================================================================================================
Installing:
kernel x86_64 2.6.32-642.3.1.el6 rhui-REGION-rhel-server-releases 32 M
Updating:
autofs x86_64 1:5.0.5-123.el6_8 rhui-REGION-rhel-server-releases 721 k
elasticsearch noarch 2.3.5-1 elasticsearch-2.x 26 M
httpd x86_64 2.2.15-54.el6_8 rhui-REGION-rhel-server-releases 833 k
httpd-tools x86_64 2.2.15-54.el6_8 rhui-REGION-rhel-server-releases 78 k
initscripts x86_64 9.03.53-1.el6_8.1 rhui-REGION-rhel-server-releases 947 k
java-1.7.0-openjdk x86_64 1:1.7.0.111-2.6.7.2.el6_8 rhui-REGION-rhel-server-releases 26 M
kernel-firmware noarch 2.6.32-642.3.1.el6 rhui-REGION-rhel-server-releases 28 M
kernel-headers x86_64 2.6.32-642.3.1.el6 rhui-REGION-rhel-server-releases 4.4 M
libcgroup x86_64 0.40.rc1-18.el6_8 rhui-REGION-rhel-server-releases 130 k
libipa_hbac x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 112 k
libsss_idmap x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 118 k
libtiff x86_64 3.9.4-18.el6_8 rhui-REGION-rhel-server-releases 345 k
libxml2 x86_64 2.7.6-21.el6_8.1 rhui-REGION-rhel-server-releases 805 k
libxml2-python x86_64 2.7.6-21.el6_8.1 rhui-REGION-rhel-server-releases 325 k
mdadm x86_64 3.3.4-1.el6_8.5 rhui-REGION-rhel-server-releases 348 k
mod_ssl x86_64 1:2.2.15-54.el6_8 rhui-REGION-rhel-server-releases 97 k
nfs-utils x86_64 1:1.2.3-70.el6_8.1 rhui-REGION-rhel-server-releases 335 k
nss-softokn x86_64 3.14.3-23.3.el6_8 rhui-REGION-rhel-server-releases 262 k
nss-softokn-freebl x86_64 3.14.3-23.3.el6_8 rhui-REGION-rhel-server-releases 168 k
perf x86_64 2.6.32-642.3.1.el6 rhui-REGION-rhel-server-releases 4.6 M
php56w x86_64 5.6.24-1.w6 webtatic 2.7 M
php56w-cli x86_64 5.6.24-1.w6 webtatic 2.6 M
php56w-common x86_64 5.6.24-1.w6 webtatic 1.2 M
php56w-gd x86_64 5.6.24-1.w6 webtatic 144 k
php56w-mbstring x86_64 5.6.24-1.w6 webtatic 944 k
php56w-mcrypt x86_64 5.6.24-1.w6 webtatic 25 k
php56w-mysql x86_64 5.6.24-1.w6 webtatic 111 k
php56w-pdo x86_64 5.6.24-1.w6 webtatic 94 k
php56w-process x86_64 5.6.24-1.w6 webtatic 35 k
php56w-tidy x86_64 5.6.24-1.w6 webtatic 29 k
php56w-xml x86_64 5.6.24-1.w6 webtatic 148 k
python-libipa_hbac x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 107 k
python-sssdconfig noarch 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 141 k
samba4-libs x86_64 4.2.10-7.el6_8 rhui-REGION-rhel-server-releases 4.4 M
sssd x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 108 k
sssd-ad x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 211 k
sssd-client x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 164 k
sssd-common x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 1.1 M
sssd-common-pac x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 147 k
sssd-ipa x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 277 k
sssd-krb5 x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 143 k
sssd-krb5-common x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 163 k
sssd-ldap x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 209 k
sssd-proxy x86_64 1.13.3-22.el6_8.4 rhui-REGION-rhel-server-releases 137 k
tar x86_64 2:1.23-15.el6_8 rhui-REGION-rhel-server-releases 810 k
tzdata noarch 2016f-1.el6 rhui-REGION-rhel-server-releases 452 k
tzdata-java noarch 2016f-1.el6 rhui-REGION-rhel-server-releases 180 k
yum noarch 3.2.29-75.el6_8 rhui-REGION-rhel-server-releases 1.0 M
Removing:
kernel x86_64 2.6.32-573.18.1.el6 @rhui-REGION-rhel-server-releases 126 M
Transaction Summary
================================================================================================================================================================
Install 1 Package(s)
Upgrade 48 Package(s)
Remove 1 Package(s)
Total download size: 144 M
我的问题是：
- 如何确保重启后 ssh 已启动？我被锁定在服务器之外。
- 我高度怀疑其中一个包有错误，但我不知道是哪个。有什么方法可以查明错误原因吗？
答案1
错误connection refused可能意味着sshd服务未启动，因此没有按应有的方式监听端口 22。
在重启之前，更新软件包之后，请检查OpenSSH仍在运行telnet localhost 22，telnet请yum install telnet键入OpenSSH横幅，则表示正在运行，请telnet键入^](control-]) 退出。如果没有，则表示更新过程失败。请尝试以下操作来查看更新的状态sshd服务：
非 systemd（CentOS 7 之前）
# chkconfig --列表 sshd
如果您看到它off，请使用以下命令启用它：
# chkconfig sshd 开启
然后启动它：
# 启动 sshd 服务
重试telnet。如果仍然没有响应，请检查/var/log/messages并找出拒绝启动的原因。
使用 systemd（CentOS 7 及更高版本）：
#systemctl 状态 sshd -l
此命令应告诉您上次尝试启动时发生了什么sshd。如果它显示sshd不是enabled，则意味着它不会在启动时启动，请使用以下命令启用它：
#systemctl 启用 sshd
如果没有响应就启动它：
#systemctl 启动 sshd
再次检查启动过程如何systemctl status sshd，过程中发生的错误应该显示在控制台中。
至于有关调试yum更新过程的问题，您可能希望将值debuglevel从 2（默认值）上升到 10（更高值）/etc/yum.conf。