为什么将 sudo umount /mnt 放入 shell 脚本中执行失败，但在命令行中执行成功？

Question

当我在环境中执行以下脚本时Debian 12 live，我发现在这个脚本中无法执行umount /mnt。提示是/mnt : target is busy. 但是，脚本执行后，我能够sudo umount /mnt在命令行上成功执行。我已经给这个脚本添加了777权限。问题是什么？

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#!/usr/bin/bash\nset +x\ncurrent_path=$(pwd)\necho $current_path\nhdstr=/dev/mmcblk0\nhdstr1=${hdstr}p1\nhdstr2=${hdstr}p2\nhdstr3=${hdstr}p3\n\nroot_path=/mnt\nboot_path=${root_path}/boot\ngrub_path=${boot_path}/grub\nefi_path=${boot_path}/efi\n\nlib64_path=${root_path}/lib64\nbin_path=${root_path}/bin\nlib_path=${root_path}/lib\n\necho "debug:function definition"\n    \nexecute_command() {\n    local command=$1\n    eval "$command"\n    local status=$?\n    if [ $status -eq 0 ]; then\n        echo "run the cmd:$command success"\n    else\n        echo "failed to run the cmd:$command" \n        exit 1\n    fi\n}\n\nadd_env_for_chroot() {\n    echo "add env for chroot"\n    execute_command "sudo mkdir -p ${lib64_path}"\n    execute_command "sudo ln -s ${lib_path} ${lib64_path}"\n    execute_command "sudo cp ${lib_path}/* ${lib64_path}/ -nra"\n}\n\n\nchange_root() {\n    echo "change root"\n    #execute_command "sudo mount --rbind /dev  /mnt/dev"\n    #execute_command "sudo mount --rbind /proc /mnt/proc"\n    #execute_command "sudo mount --rbind /sys  /mnt/sys"\n    execute_command "sudo mount -t proc proc /mnt/proc"\n    execute_command "sudo mount -t sysfs sys /mnt/sys"\n    execute_command "sudo mount -o bind /dev /mnt/dev"\n    execute_command "sudo mount --bind /run /mnt/run"\n    add_env_for_chroot\n\n    \n    cat << EOF | sudo chroot ${root_path}\n    grub-install --target=x86_64-efi /dev/mmcblk0 --force --recheck --efi-directory=/boot/efi \n    exit\nEOF\n}\n\ncreate_fstab() {\n    echo "create fstab"\n    UUID1=$(sudo blkid | grep '^/dev/mmcblk0p1' | awk -F 'UUID="' '{print $2}' | awk -F '"' '{print $1}')\n    UUID2=$(sudo blkid | grep '^/dev/mmcblk0p2' | awk -F 'UUID="' '{print $2}' | awk -F '"' '{print $1}')\n    UUID3=$(sudo blkid | grep '^/dev/mmcblk0p3' | awk -F 'UUID="' '{print $2}' | awk -F '"' '{print $1}')\n    #\xe8\xbf\x99\xe9\x87\x8c\xe4\xb8\x8d\xe6\x9b\xbf\xe6\x8d\xa2sda\n    devName="\\/dev\\/mmcblk0p1"\n    UUIDStr="UUID=$UUID1"\n    execute_command "sed -i \\"s/${devName}/${UUIDStr}/g\\"  /mnt/etc/fstab"\n    \n    devName="\\/dev\\/mmcblk0p2"\n    UUIDStr="UUID=$UUID2"\n    execute_command "sed -i \\"s/${devName}/${UUIDStr}/g\\"  /mnt/etc/fstab"\n    \n    devName="\\/dev\\/mmcblk0p3"\n    UUIDStr="UUID=$UUID3"\n    execute_command "sed -i \\"s/${devName}/${UUIDStr}/g\\"  /mnt/etc/fstab"\n}\n\npartition_format_mount() {\n    echo "begin to part"\n    ####partition####\n    sudo /sbin/parted ${hdstr} mklabel gpt\n    sudo /sbin/parted ${hdstr} <<EOT 1>/dev/null 2>/dev/null || exit 1\n    rm 1\n    rm 2\n    rm 3\n    rm 4\n    mkpart primary fat32 1MiB 200MiB\n    set 1 esp on\n    mkpart primary ext4 200MiB 8200MiB\n    mkpart primary ext4 8200MiB 100%\n    quit\nEOT\n    echo ""\n    ####format####\n    echo "begin to format"\n    #execute_command "sudo partx ${hdstr} 1>/dev/null"\n    execute_command "sudo /sbin/mkfs.fat -F32 ${hdstr1} 1>/dev/null"\n    execute_command "sudo /sbin/mkfs.ext4 ${hdstr2} 1>/dev/null"\n    execute_command "sudo /sbin/mkfs.ext4 ${hdstr3} 1>/dev/null"\n    \n    execute_command "sudo /sbin/fsck.vfat -v -a -w ${hdstr1} 1>/dev/null"\n    execute_command "sudo /sbin/fsck.ext4 ${hdstr2}"\n    execute_command "sudo /sbin/fsck.ext4 ${hdstr3}"\n    ####mount####\n    execute_command "sudo mkdir -p ${root_path}"\n    execute_command "sudo mount ${hdstr3} ${root_path} 1>/dev/null"\n    execute_command "sudo mkdir ${boot_path} -p"\n    execute_command "sudo mount ${hdstr2} ${boot_path} 1>/dev/null"\n    execute_command "sudo mkdir ${efi_path} -p"\n    execute_command "sudo mount ${hdstr1} ${efi_path} 1>/dev/null"\n    echo "end part"\n}\n\ninstall_os(){\n    echo "begin to install grub"\n    execute_command "sudo mkdir -p ${grub_path}"\n    execute_command "sudo cp ${current_path}/grub_CRA.cfg ${grub_path}/grub.cfg"\n\n\n    #execute_command "sudo cp ${current_path}/x86_64-efi  /usr/lib/grub/  -raf"  #issue1\n    execute_command "sudo cp \\"${current_path}/bzImage\\" ${boot_path}/"        #2024-1-19 \xe4\xbf\xae\xe6\x94\xb9bzImage\xe8\xb7\xaf\xe5\xbe\x84\n    execute_command "sudo cp \\"${current_path}/initrd.img-6.4.0-rt8\\" ${boot_path}"  #2024-1-19 \xe4\xbf\xae\xe6\x94\xb9initrd\xe8\xb7\xaf\xe5\xbe\x84\n    execute_command "sudo cp \\"${current_path}/rootfs.tar.gz\\" ${root_path}"\n    cd ${root_path}\n    execute_command "sudo tar -vxf rootfs.tar.gz"\n    execute_command "echo \\"y\\" | sudo rm rootfs.tar.gz"\n    echo "begin to changerooot" \n    change_root\n    create_fstab\n    \n    echo "start to umount"  \n    execute_command "sudo umount ${hdstr1} 1>/dev/null"\n    execute_command "sudo umount ${hdstr2} 1>/dev/null"\n    execute_command "sudo umount /mnt/run"\n    #execute_command "sudo umount /mnt/{proc,sys,dev}"\n    execute_command "sudo umount /mnt/proc"\n    execute_command "sudo umount /mnt/sys"\n    execute_command "sudo umount /mnt/dev"\n    #cat << EOF | sudo chroot ${root_path}\n    #echo "To successfully umount /mnt, I don't know why, but it is useful." \n    #exit\n#EOF\n    execute_command "sync"\n#==========================my question in here=============================\n    sudo umount /mnt \n#==========================================================================\n#   execute_command "sudo umount ${hdstr3} 1>/dev/null"\n    #sudo /sbin/fsck.vfat -a ${hdstr1}\n    #sudo /sbin/fsck.ext4 -a ${hdstr2}\n    #sudo /sbin/fsck.ext4 -a ${hdstr3}\n    execute_command "sync" \n}\n\nmainFunc(){\n    echo "start to burn"\n    partition_format_mount\n    install_os    \n}\n\nmainFunc\n

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Answer 1

您已经获得了相当于cd /mnt脚本上方的内容，因此您位于尝试卸载的目录中。

这里还需要考虑其他一些大问题：

1. 脚本中的几乎每个命令都在 下运行sudo，因此请考虑删除所有这些调用sudo并要求脚本本身在 下运行sudo。

   #!/bin/bash
   if [ "$(id -u)" -ne 0 ]
   then
       echo "Please re-run with sudo" >&2
       exit 1
   fi
   

   或者甚至让脚本自动重新运行sudo：

   #!/bin/bash
   if [ "$(id -u)" -ne 0 ]
   then
       echo "Re-running with sudo" >&2
       exec sudo "$0" "$@"
       exit 1
   fi
   

2. 您将命令存储在变量中。这可能会导致各种与引用相关的问题，而您使用eval. 变量用于数据，函数用于命令：

   execute_command() {
       if "$@"
       then
           echo "ran $1 successfully" >&2
       else
           echo "failed to run $1" >&2
           exit 1
       fi
   }
   
   execute_command sudo umount /mnt/proc
   

   但实际上，这可以简单地通过在第一行设置-e（或者可能是-ex，该-x标志启用逐行跟踪）或使用set -eand 可能set -x不久之后来实现。例如，

   #!/bin/bash -ex
   echo "this line succeeds"
   echo "the next line will fail"
   false
   echo "the script has already stopped so you will not see this"
   exit 0
   

3. 您没有对任何变量进行双引号。这意味着每当您使用它们时，它们都会受到分裂和通配符的影响。

4. “我已经为此脚本添加了 777 权限” - 可能不需要允许其他用户编辑此脚本，因此不要放弃该权利。最多允许其他用户运行该脚本：

   chmod u=rwx,go=rx ./your_script    # Replace "./yourscript" with the script path