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？

2024-6-20 • tag-icon

linux debian shell

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？

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？

#!/usr/bin/bash
set +x
current_path=$(pwd)
echo $current_path
hdstr=/dev/mmcblk0
hdstr1=${hdstr}p1
hdstr2=${hdstr}p2
hdstr3=${hdstr}p3

root_path=/mnt
boot_path=${root_path}/boot
grub_path=${boot_path}/grub
efi_path=${boot_path}/efi

lib64_path=${root_path}/lib64
bin_path=${root_path}/bin
lib_path=${root_path}/lib

echo "debug:function definition"
    
execute_command() {
    local command=$1
    eval "$command"
    local status=$?
    if [ $status -eq 0 ]; then
        echo "run the cmd:$command success"
    else
        echo "failed to run the cmd:$command" 
        exit 1
    fi
}

add_env_for_chroot() {
    echo "add env for chroot"
    execute_command "sudo mkdir -p ${lib64_path}"
    execute_command "sudo ln -s ${lib_path} ${lib64_path}"
    execute_command "sudo cp ${lib_path}/* ${lib64_path}/ -nra"
}


change_root() {
    echo "change root"
    #execute_command "sudo mount --rbind /dev  /mnt/dev"
    #execute_command "sudo mount --rbind /proc /mnt/proc"
    #execute_command "sudo mount --rbind /sys  /mnt/sys"
    execute_command "sudo mount -t proc proc /mnt/proc"
    execute_command "sudo mount -t sysfs sys /mnt/sys"
    execute_command "sudo mount -o bind /dev /mnt/dev"
    execute_command "sudo mount --bind /run /mnt/run"
    add_env_for_chroot

    
    cat << EOF | sudo chroot ${root_path}
    grub-install --target=x86_64-efi /dev/mmcblk0 --force --recheck --efi-directory=/boot/efi 
    exit
EOF
}

create_fstab() {
    echo "create fstab"
    UUID1=$(sudo blkid | grep '^/dev/mmcblk0p1' | awk -F 'UUID="' '{print $2}' | awk -F '"' '{print $1}')
    UUID2=$(sudo blkid | grep '^/dev/mmcblk0p2' | awk -F 'UUID="' '{print $2}' | awk -F '"' '{print $1}')
    UUID3=$(sudo blkid | grep '^/dev/mmcblk0p3' | awk -F 'UUID="' '{print $2}' | awk -F '"' '{print $1}')
    #这里不替换sda
    devName="\/dev\/mmcblk0p1"
    UUIDStr="UUID=$UUID1"
    execute_command "sed -i \"s/${devName}/${UUIDStr}/g\"  /mnt/etc/fstab"
    
    devName="\/dev\/mmcblk0p2"
    UUIDStr="UUID=$UUID2"
    execute_command "sed -i \"s/${devName}/${UUIDStr}/g\"  /mnt/etc/fstab"
    
    devName="\/dev\/mmcblk0p3"
    UUIDStr="UUID=$UUID3"
    execute_command "sed -i \"s/${devName}/${UUIDStr}/g\"  /mnt/etc/fstab"
}

partition_format_mount() {
    echo "begin to part"
    ####partition####
    sudo /sbin/parted ${hdstr} mklabel gpt
    sudo /sbin/parted ${hdstr} <<EOT 1>/dev/null 2>/dev/null || exit 1
    rm 1
    rm 2
    rm 3
    rm 4
    mkpart primary fat32 1MiB 200MiB
    set 1 esp on
    mkpart primary ext4 200MiB 8200MiB
    mkpart primary ext4 8200MiB 100%
    quit
EOT
    echo ""
    ####format####
    echo "begin to format"
    #execute_command "sudo partx ${hdstr} 1>/dev/null"
    execute_command "sudo /sbin/mkfs.fat -F32 ${hdstr1} 1>/dev/null"
    execute_command "sudo /sbin/mkfs.ext4 ${hdstr2} 1>/dev/null"
    execute_command "sudo /sbin/mkfs.ext4 ${hdstr3} 1>/dev/null"
    
    execute_command "sudo /sbin/fsck.vfat -v -a -w ${hdstr1} 1>/dev/null"
    execute_command "sudo /sbin/fsck.ext4 ${hdstr2}"
    execute_command "sudo /sbin/fsck.ext4 ${hdstr3}"
    ####mount####
    execute_command "sudo mkdir -p ${root_path}"
    execute_command "sudo mount ${hdstr3} ${root_path} 1>/dev/null"
    execute_command "sudo mkdir ${boot_path} -p"
    execute_command "sudo mount ${hdstr2} ${boot_path} 1>/dev/null"
    execute_command "sudo mkdir ${efi_path} -p"
    execute_command "sudo mount ${hdstr1} ${efi_path} 1>/dev/null"
    echo "end part"
}

install_os(){
    echo "begin to install grub"
    execute_command "sudo mkdir -p ${grub_path}"
    execute_command "sudo cp ${current_path}/grub_CRA.cfg ${grub_path}/grub.cfg"


    #execute_command "sudo cp ${current_path}/x86_64-efi  /usr/lib/grub/  -raf"  #issue1
    execute_command "sudo cp \"${current_path}/bzImage\" ${boot_path}/"        #2024-1-19 修改bzImage路径
    execute_command "sudo cp \"${current_path}/initrd.img-6.4.0-rt8\" ${boot_path}"  #2024-1-19 修改initrd路径
    execute_command "sudo cp \"${current_path}/rootfs.tar.gz\" ${root_path}"
    cd ${root_path}
    execute_command "sudo tar -vxf rootfs.tar.gz"
    execute_command "echo \"y\" | sudo rm rootfs.tar.gz"
    echo "begin to changerooot" 
    change_root
    create_fstab
    
    echo "start to umount"  
    execute_command "sudo umount ${hdstr1} 1>/dev/null"
    execute_command "sudo umount ${hdstr2} 1>/dev/null"
    execute_command "sudo umount /mnt/run"
    #execute_command "sudo umount /mnt/{proc,sys,dev}"
    execute_command "sudo umount /mnt/proc"
    execute_command "sudo umount /mnt/sys"
    execute_command "sudo umount /mnt/dev"
    #cat << EOF | sudo chroot ${root_path}
    #echo "To successfully umount /mnt, I don't know why, but it is useful." 
    #exit
#EOF
    execute_command "sync"
#==========================my question in here=============================
    sudo umount /mnt 
#==========================================================================
#   execute_command "sudo umount ${hdstr3} 1>/dev/null"
    #sudo /sbin/fsck.vfat -a ${hdstr1}
    #sudo /sbin/fsck.ext4 -a ${hdstr2}
    #sudo /sbin/fsck.ext4 -a ${hdstr3}
    execute_command "sync" 
}

mainFunc(){
    echo "start to burn"
    partition_format_mount
    install_os    
}

mainFunc

答案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：

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

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

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。
”我已经给这个脚本添加了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
```

答案2

在卸载分区之前，您需要退出 chroot 环境。通过exit命令。

使用 bash getopts，使您的脚本接受卸载函数作为参数。或者使用trap在 bash 脚本退出时执行函数：

unmount_fscks (){
commands_umount_fsck_here
}

trap 'unmount_fscks' EXIT

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