Linux Shell 脚本：如何检测 NFS 挂载点（或服务器）已死？
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Linux Shell Script: How to detect NFS Mount-point (or the Server) is dead?
提问by u775856
Generally on NFS Client, how to detect the Mounted-Point is no more available or DEAD from Server-end, by using the Bash Shell Script?
通常在 NFS 客户端上，如何通过使用 Bash Shell 脚本检测服务器端的挂载点不再可用或死机？
Normally i do:
通常我这样做：
if ls '/var/data' 2>&1 | grep 'Stale file handle';
then
echo "failing";
else
echo "ok";
fi
But the problem is, when especially the NFS Server is totally dead or stopped, even the, lscommand, into that directory, at Client-side is hanged or died. Means, the script above is no more usable.
但问题是，尤其是当 NFS 服务器完全死机或停止时，即使是ls进入该目录的命令，在客户端也会被挂起或死机。意味着，上面的脚本不再可用。
Is there any way to detect this again please?
请问有什么办法可以再次检测到吗？
回答by Ville
"stat" command is a somewhat cleaner way:
“stat”命令是一种更简洁的方法：
statresult=`stat /my/mountpoint 2>&1 | grep -i "stale"`
if [ "${statresult}" != "" ]; then
#result not empty: mountpoint is stale; remove it
umount -f /my/mountpoint
fi
Additionally, you can use rpcinfo to detect whether the remote nfs share is available:
此外，您可以使用 rpcinfo 来检测远程 nfs 共享是否可用：
rpcinfo -t remote.system.net nfs > /dev/null 2>&1
if [ $? -eq 0 ]; then
echo Remote NFS share available.
fi
Added 2013-07-15T14:31:18-05:00:
添加 2013-07-15T14:31:18-05:00：
I looked into this further as I am also working on a script that needs to recognize stale mountpoints. Inspired by one of the repliesto "Is there a good way to detect a stale NFS mount", I think the following may be the most reliable way to check for staleness of a specific mountpoint in bash:
我进一步研究了这一点，因为我还在编写一个需要识别过时挂载点的脚本。受到对“是否有一种检测陈旧 NFS 挂载的好方法”的答复之一的启发，我认为以下可能是检查 bash 中特定挂载点是否陈旧的最可靠方法：
read -t1 < <(stat -t "/my/mountpoint")
if [ $? -eq 1 ]; then
echo NFS mount stale. Removing...
umount -f -l /my/mountpoint
fi
"read -t1" construct reliably times out the subshell if stat command hangs for some reason.
如果 stat 命令由于某种原因挂起，“read -t1”构造会可靠地使子shell超时。
Added 2013-07-17T12:03:23-05:00:
添加 2013-07-17T12:03:23-05:00：
Although read -t1 < <(stat -t "/my/mountpoint")works, there doesn't seem to be a way to mute its error output when the mountpoint is stale. Adding > /dev/null 2>&1either within the subshell, or in the end of the command line breaks it. Using a simple test: if [ -d /path/to/mountpoint ] ; then ... fialso works, and may preferable in scripts. After much testing it is what I ended up using.
虽然read -t1 < <(stat -t "/my/mountpoint")有效，但似乎没有办法在挂载点陈旧时将其错误输出静音。> /dev/null 2>&1在子shell中或在命令行的末尾添加会破坏它。使用简单的测试：if [ -d /path/to/mountpoint ] ; then ... fi也可以使用，并且在脚本中可能更可取。经过多次测试，这是我最终使用的。
Added 2013-07-19T13:51:27-05:00:
添加 2013-07-19T13:51:27-05:00：
A reply to my question "How can I use read timeouts with stat?" provided additional detail about muting the output of stat (or rpcinfo) when the target is not available and the command hangs for a few minutes before it would time out on its own. While [ -d /some/mountpoint ]can be used to detect a stale mountpoint, there is no similar alternative for rpcinfo, and hence use of read -t1redirection is the best option. The output from the subshell can be muted with 2>&-. Here is an example from CodeMonkey's response:
对我的问题“如何将读取超时与 stat 一起使用？”的回复提供了有关在目标不可用且命令挂起几分钟前将 stat（或 rpcinfo）的输出静音的更多详细信息，然后它会超时自己的。虽然[ -d /some/mountpoint ]可用于检测过时的挂载点，但 rpcinfo 没有类似的替代方法，因此使用read -t1重定向是最佳选择。子shell的输出可以用2>&-静音。以下是CodeMonkey 响应中的一个示例：
mountpoint="/my/mountpoint"
read -t1 < <(stat -t "$mountpoint" 2>&-)
if [[ -n "$REPLY" ]]; then
echo "NFS mount stale. Removing..."
umount -f -l "$mountpoint"
fi
Perhaps now this question is fully answered :).
也许现在这个问题得到了充分的回答:)。
回答by et071385
The final answers give by Ville and CodeMonkey are almost correct. I'm not sure how no one noticed this, but a $REPLY string having content is a success, not a failure. Thus, an empty$REPLY string means the mount is stale. Thus, the conditional should use -z, not -n:
Ville 和 CodeMonkey 给出的最终答案几乎是正确的。我不确定怎么没有人注意到这一点，但是包含内容的 $REPLY 字符串是成功的，而不是失败的。因此，空的$REPLY 字符串表示挂载已过时。因此，条件应该使用 -z，而不是 -n：
mountpoint="/my/mountpoint"
read -t1 < <(stat -t "$mountpoint" 2>&-)
if [ -z "$REPLY" ] ; then
echo "NFS mount stale. Removing..."
umount -f -l "$mountpoint"
fi
I have ran this multiple times with a valid and invalid mount point and it works. The -n check gave me reverse results, echoing the mount was stale when it was absolutely valid.
我已经使用有效和无效的挂载点多次运行它并且它有效。-n 检查给了我相反的结果，当它绝对有效时回显安装是陈旧的。
Also, the double bracket isn't necessary for a simple string check.
此外，简单的字符串检查不需要双括号。
回答by jimbolino
with "-z" I get a NFS stale but it's totaly wrong, I can accces to it and read and write a file
使用“-z”我得到一个 NFS 陈旧但它完全错误，我可以访问它并读取和写入文件
