确定主机是否在线

Question

我正在测试机器的稳定性，我需要简单地编写一个 Bash 脚本来确定主机是否在线。我怎么能写这个？

if [ ! $(hostisonline) ]; then
    # profit
fi

Answer 1

如果主机回答 ping 然后测试它是否在线（只是一个例子）：

ping -c 10 $host

如果没有返回/禁止 ping，我会通过 nmap 检查单个服务：

nmap $host -p $known_port --max-retries 10 | grep -q open

例如要测试 ssh 是否有望打开，请将 known_port 替换为 22

至于脚本，它可能是（示例——这是星期天早上，我很无聊，所以经过一些编辑后它有所增长——旨在测试一堆主机，而不仅仅是一个）：

declare -A SERVER
# SERVER["NAME - Description"]="IP KNOWNPORT"
SERVER["SERVER1 - Client foo"]="111.111.111.111 22"
SERVER["SERVER2 - Client bar"]="222.222.222.222 80"
# ...
# add as many server/port combinations as you'd like

NMAP_MAX_RETRIES=10

printf "========================= ========================= ========== ==========\n"
printf "%25s %25s %10s %10s\n" "Host Description" "IP" "Port" "Status"
printf "========================= ========================= ========== ==========\n"


for server in "${!SERVER[@]}"; do
    set -- ${SERVER["$server"]}
    eval nmap \$1 -p \$2 --max-retries $NMAP_MAX_RETRIES | grep -q open
    if [ "$?" == "0" ]; then
        STATUS="[OK]"
    else
        STATUS="*DOWN*" 
    fi
    printf "%25s %25s %10s %10s\n" "$server" "$1" "$2" "$STATUS" 
done

 printf "========================= ========================= ========== ==========\n"

执行时它返回（假ips，所以服务器关闭）：

 ~$ bash /tmp/foo.sh
 ========================= ========================= ========== ==========
          Host Description                        IP       Port     Status
 ========================= ========================= ========== ==========
      SERVER2 - Client bar           222.222.222.222         80     *DOWN*
      SERVER1 - Client foo           111.111.111.111         22     *DOWN*
 ========================= ========================= ========== ==========

Answer 2

一个简单的解决方案是：

ping -W 1 $ip

其中-W以秒为单位指定超时。

确保它是大写的 W。您还可以使用-i以秒为单位指定等待时间。