无法弄清楚 fail2ban 日志错误消息：“iptables -n -L INPUT | grep -q 'fail2ban-SSH[ \t]' 返回 100”

Question

这是我的 ssh 的 jail.local 规则：

[ssh-iptables]

enabled  = true
filter   = sshd
action   = iptables[name=SSH, port=ssh, protocol=tcp]
logpath  = /var/log/messages
maxretry = 5

以下是我的日志使用 BAN 生成的内容

2015-04-23 07:07:49,823 fail2ban.actions[27564]: WARNING [ssh-tcpwrapper] Ban xx.xx.xxx.xxx
2015-04-23 07:07:50,721 fail2ban.actions[27564]: WARNING [ssh-iptables] Ban xx.xx.xxx.xxx
2015-04-23 07:07:50,729 fail2ban.actions.action[27564]: ERROR   iptables -n -L INPUT | grep -q 'fail2ban-SSH[ \t]' returned 100
2015-04-23 07:07:50,730 fail2ban.actions.action[27564]: ERROR   Invariant check failed. Trying to restore a sane environment
2015-04-23 07:07:50,738 fail2ban.actions.action[27564]: ERROR   iptables -D INPUT -p tcp --dport ssh -j fail2ban-SSH
iptables -F fail2ban-SSH
iptables -X fail2ban-SSH returned 100

现在我也通过 UNBAN 遇到了这个问题：

2015-04-23 16:18:48,828 fail2ban.actions[27564]: WARNING [ssh-tcpwrapper] Unban xx.xx.xxx.xxx
2015-04-23 16:18:48,835 fail2ban.actions.action[27564]: ERROR   echo "/^sshd: xx.xx.xxx.xxx$/
d
w
q" | ed /etc/hosts.deny returned 7f00
2015-04-23 16:18:48,836 fail2ban.actions.action[27564]: INFO    HINT on 7f00: "Command not found".  Make sure that all commands in 'echo "/^sshd: xx.xx.xxx.xxx$/\nd\nw\nq" | ed /etc/hosts.deny' are in the PATH of fail2ban-server process (grep -a PATH= /proc/`pidof -x fail2ban-server`/environ). You may want to start "fail2ban-server -f" separately, initiate it with "fail2ban-client reload" in another shell session and observe if additional informative error messages appear in the terminals.
2015-04-23 16:19:04,847 fail2ban.actions[27564]: WARNING [ssh-iptables] Unban xx.xx.xxx.xxx
2015-04-23 16:19:04,855 fail2ban.actions.action[27564]: ERROR   iptables -n -L INPUT | grep -q 'fail2ban-SSH[ \t]' returned 100
2015-04-23 16:19:04,855 fail2ban.actions.action[27564]: ERROR   Invariant check failed. Trying to restore a sane environment
2015-04-23 16:19:04,863 fail2ban.actions.action[27564]: ERROR   iptables -D INPUT -p tcp --dport ssh -j fail2ban-SSH
iptables -F fail2ban-SSH
iptables -X fail2ban-SSH returned 100

这发生在 OpenSuse 13.2 上，其 fail2ban 安装相对未受影响。我更喜欢 Centos，我已经习惯了这种开箱即用的东西。我真的不知道如何处理这些错误，花了几个小时在谷歌上搜索并查看堆栈，但除了“删除并重新安装”之外，没有真正可靠的解决方案。

我最好的猜测是，这是一个环境问题，并且 fail2ban 服务无法发出命令和/或命令格式不正确，但我不知道具体去哪里解决这个问题。