使用 sys/mount.h 挂载 ISO

Mounting an ISO with sys/mount.h

本文关键字：挂载 ISO mount sys 使用      更新时间：2023-10-16

我正在尝试在 Linux 的C++程序中挂载 ISO 文件

我知道 linux 命令来实现这一点，即挂载 -o 循环 ~/Test.iso/mnt/myISO

但是 mount（2） 手册页指出了以下挂载原型： 

int mount(const char *source, const char *target,
const char *filesystemtype, unsigned long mountflags,
const void *data);

如何在此处指定循环选项？

--

另外，在

linux 编程中，使用来自C++的系统 shell 调用来完成这些任务通常是好的（/可接受的）做法吗？

小例子

#include <sys/mount.h>
#include <linux/loop.h>
#include <fcntl.h>
int main()
{
    int file_fd, device_fd;
    file_fd = open("./TVM_TOMI1.iso", O_RDWR);
    if (file_fd < -1) {
        perror("open backing file failed");
        return 1;
    }
    device_fd = open("/dev/loop0", O_RDWR);
    if (device_fd < -1) {
        perror("open loop device failed");
        close(file_fd);
        return 1;
    }
    if (ioctl(device_fd, LOOP_SET_FD, file_fd) < 0) {
        perror("ioctl LOOP_SET_FD failed");
        close(file_fd);
        close(device_fd);
        return 1;
    }
    close(file_fd);
    close(device_fd);
    mount("/dev/loop0","/mnt/iso","iso9660",MS_RDONLY,"");
}

更新：卸载后，您需要自由循环：

device_fd = open("/dev/loop0", O_RDWR);
...
if (ioctl(device_fd, LOOP_CLR_FD, 0) < 0) {
    perror("ioctl LOOP_CLR_FD failed");
    return 1;
}

这是一个代码，它也为你创建循环设备。请注意不要在生产中使用此类代码，因为没有对返回值、异常等:)进行单一检查。

#include <sys/mount.h>  //mount
#include <sys/ioctl.h>  //ioctl
#include <sys/stat.h>   //open
#include <linux/loop.h> //LOOP_SET_FD
#include <fcntl.h>      //open
#include <cstdio>       // declaration of ::fileno
#include <cstdint>      //int32_t
#include <sstream>      //std::stringstream
#include <string>
constexpr char IMAGE_NAME[] = "image.iso";       //of course we need this file to be present in same folder as built tool
constexpr char MOUNT_POINT[] = "/tmp/image_mnt"; //of course we need this folder already created
constexpr char FILESYSTEM_TYPE[] = "iso9660";
constexpr char DEV_LOOP_CONTROL[] = "/dev/loop-control";
constexpr char DEV_LOOP_PREFIX[] = "/dev/loop";
constexpr int32_t MOUNT_FLAGS = MS_RDONLY;
int main()
{
    const auto loop_control = std::fopen(DEV_LOOP_CONTROL, "r");
    const auto loop_control_fd = fileno(loop_control);
    const auto devnr = ioctl(loop_control_fd, LOOP_CTL_GET_FREE);
    std::stringstream loopname;
    loopname << DEV_LOOP_PREFIX << devnr;
    const auto loop_device_name = loopname.str();
    const auto loop_device = std::fopen(loop_device_name.c_str(), "r");
    const auto loop_device_fd = fileno(loop_device);
    const auto image = std::fopen(IMAGE_NAME, "r");
    const auto image_fd = fileno(image);
    //Associate the loop device with the open file whose file descriptor is passed as the (third) ioctl(2) argument.
    ioctl(loop_device_fd, LOOP_SET_FD, image_fd);
    const auto result = mount(loop_device_name.c_str(), MOUNT_POINT, FILESYSTEM_TYPE, MOUNT_FLAGS, NULL);
    ioctl(loop_device_fd, LOOP_CLR_FD, 0);
    return result;
}

基于：

http://man7.org/linux/man-pages/man4/loop.4.html
https://linux.die.net/man/2/mount

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