如何在不知道挂载点的情况下知道设备UUID已挂载？

debugcn 发表于 Dev

LinuxSecurityFreak

系统：基于Ubuntu 18.04 LTS的Linux Mint 19.1 Cinnamon 64位。

我想知道是否有可能获得以下信息：

是否已安装（块设备的）UUID？（不知道安装点）

尽管如此，我已经玩了半天，但我无法弄清楚。

我至少创建了一些工作代码，在这些代码下，这两个USB硬盘驱动器均会卸装并关闭电源。

我的代码的当前临时版本如下所示：

dismount_and_poweroff_external_drives()
{
    name_external_drive_500gb_ntfs='500GB NTFS USB 2.0 HDD'
    name_external_drive_2_0tb_ext4='2.0TB Ext4 USB 3.0 HDD'
    uuid_external_drive_500gb_ntfs='xxxxxxxxxxxxxxxx' # censored
    uuid_external_drive_2_0tb_ext4='xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx' # censored
    path_external_drive_500gb_ntfs="/dev/disk/by-uuid/${uuid_external_drive_500gb_ntfs}"
    path_external_drive_2_0tb_ext4="/dev/disk/by-uuid/${uuid_external_drive_2_0tb_ext4}"

    tput bold; tput setaf 3; printf '%b' "\\n${name_external_drive_500gb_ntfs} un-mount\\n"; tput sgr0
    # info test ‘-b FILE’: True if FILE exists and is a block special device.
    if [ ! -b "${path_external_drive_500gb_ntfs}" ]
    then
        tput bold; tput setaf 4; printf '%b' "The device is not plugged in or powered on.\\n"; tput sgr0
    else
        if umount "${path_external_drive_500gb_ntfs}"
        then
            tput bold; tput setaf 2; printf '%b' "Un-mounting OK.\\n"; tput sgr0

            if udisksctl power-off --block-device "${path_external_drive_500gb_ntfs}"
            then
                tput bold; tput setaf 2; printf '%b' "Powering-off OK.\\n"; tput sgr0
            else
                tput bold; tput setaf 1; printf '%b' "Powering-off Failed.\\n"; tput sgr0
            fi

        else
            tput bold; tput setaf 1; printf '%b' "Un-mounting Failed.\\n"; tput sgr0
        fi
    fi

    printf '\n'

    tput bold; tput setaf 3; printf '%b' "\\n${name_external_drive_2_0tb_ext4} un-mount\\n"; tput sgr0
    # info test ‘-b FILE’: True if FILE exists and is a block special device.
    if [ ! -b "${path_external_drive_2_0tb_ext4}" ]
    then
        tput bold; tput setaf 4; printf '%b' "The device is not plugged in or powered on.\\n"; tput sgr0
    else
        if umount "${path_external_drive_2_0tb_ext4}"
        then
            tput bold; tput setaf 2; printf '%b' "Un-mounting OK.\\n"; tput sgr0

            if udisksctl power-off --block-device "${path_external_drive_2_0tb_ext4}"
            then
                tput bold; tput setaf 2; printf '%b' "Powering-off OK.\\n"; tput sgr0
            else
                tput bold; tput setaf 1; printf '%b' "Powering-off Failed.\\n"; tput sgr0
            fi

        else
            tput bold; tput setaf 1; printf '%b' "Un-mounting Failed.\\n"; tput sgr0
        fi
    fi

    printf '\n'
}

我忘记强调必须接受POSIX编写的解决方案。

费兹

原始解决方案

UUID=<device_uuid>
mount | egrep $(readlink -f /dev/disk/by-uuid/${UUID}) && echo mounted

弗拉斯蒂米尔的笔记

在帮助中使用-e代替可能是一个好主意：-freadlink

-e, --canonicalize-existing   canonicalize by following every symlink in
                              every component of the given name recursively,
                              all components must exist

相比于：

-f, --canonicalize            canonicalize by following every symlink in
                              every component of the given name recursively;
                              all but the last component must exist

据我了解，可以-e保证整个路径都存在，可能会更好，需要额外的验证或引用。不幸的是，该-e选项不符合POSIX标准，所以很幸运。将所有信息保留在此处以供将来参考。

原始解决方案中没有双引号，我建议将它们与一个尾随空格一起添加作为一种安全措施，以避免例如与之sda11类似的匹配。
也可以利用POSIX定义的属性fgrep来匹配固定的字符串，甚至可以更好地匹配使用开头的从此设备开始的行grep "^dev_name"。
正如Mark Plotnick所指出的那样，mount它本身可能不是POSIX定义的，再次引用将很方便，但是无论如何，我已经将代码更改为/proc/mounts直接读取。

合理的功能

用于检查是否已安装UUID的结果函数可能类似于：

is_uuid_mounted()
{
    readlink_output=$( readlink -f /dev/disk/by-uuid/"${1}" )
    [ -n "${readlink_output}" ] &&
        grep -F "${readlink_output} " /proc/mounts > /dev/null 2>&1
}

完整的工作脚本

#!/bin/sh

set -eu

translate_uuid_to_device_name()
{
    # Linux-specific; needs *BSD revision
    readlink -f -n /dev/disk/by-uuid/"${1}"
}

is_uuid_mounted()
{
    device_name=$( translate_uuid_to_device_name "${1}" )

    if [ -n "${device_name}" ]
    then
        # 1. basic regex should be working across platfotms
        #    tested on FreeBSD, OpenBSD, NetBSD with success
        #    I prefer the starting with (^) rather than filtering throung all text
        # 2. /proc/mounts is not available on all *BSDs, needs revision
        proc_mounts=$( grep "^${device_name} " /proc/mounts )
        [ -n "${proc_mounts}" ]
    fi
}

# Simplest Usage Example
if is_uuid_mounted "PUT_SOME_UUID_IN_HERE"
then
    echo "This UUID is mounted."
else
    echo "This UUID isn't mounted."
fi

请随时在评论中解决其他问题。

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