linux中的mount系统调用无法通过df命令显示文件系统的挂载点 [英] mount system call in linux cannot display the mountpoint of file system by df command

问题描述

我正在尝试在程序中使用mount()而不是mount命令，我成功使用了以下mount()，结果返回了成功，而不是Invalid Argument.

I am trying to use mount() instead of mount command in my program, I use the following mount() successfully, the result returned success instead of Invalid Argument.

int rc = mount("172.16.74.20:/data/redun/snmp","/mnt/data/redun/snmp",
                    "nfs",0,"soft,timeo=2,addr=172.16.74.20");

if (rc != 0)
 {
     printf("mount failed, errCode=%d, reason=%s\n",errno, strerror(errno));
 }

但是当我使用df -h检查安装点时，没有任何显示. 我发现相关设备尚未安装.发生了什么?真的成功安装了吗?如何在Linux中通过df命令显示已安装的设备?

But when I use df -h to check the mountpoint, there are nothing displayed. I found the related device was not mounted yet. What happened? Is it really mounted successfully? How can I display the mounted device by df command in Linux?

推荐答案

问题在于，与mount命令不同，mount() syscall不会更新/etc/mtab文件，而df命令会解析/etc/mtab列出挂载点.

The problem is that mount() syscall, unlike mount command, doesn't update /etc/mtab file, while df command parses /etc/mtab to list mount points.

但是，安装点的最新列表始终在/proc/mounts文件中可用.与/etc/mtab不同，/proc/mounts不是常规文件，而是内核提供的虚拟文件.

However, uptodate list of mount points is always available in /proc/mounts file. Unlike /etc/mtab, /proc/mounts is not a regular file, but instead a virtual file provided by kernel.

在某些发行版中，/etc/mtab是指向/proc/mounts的符号链接.如果不是，并且您希望df工作，则可以执行以下操作:

On some distributions, /etc/mtab is a symlink to /proc/mounts. If it's not, and you want df to work, you can do the following:

cat /proc/mounts > /etc/mtab

每次mount()或umount()调用后

.

您也可以将/etc/mtab链接到/proc/mounts或更好的/proc/self/mounts，但是要您自担风险(也许某些应用程序依赖它，但这可能只是发行版中的错误).

You can also make /etc/mtab a symlink to /proc/mounts or better /proc/self/mounts, but do it on your own risk (maybe some applications depend on it, but maybe it's just a bug in your distro).

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