Debian Linux live 系统 toram：无法打开 /dev/shm 设备

我编写了一个shell脚本来从硬盘安装创建一个squashfs live系统，以便让Linux系统仅在内存中运行。

但是当我运行toram live系统时，dmesg中出现以下错误：

systemd[1]: Failed to open /dev/shm device, ignoring: Inappropriate ioctl for device

尽管出现这个错误，toram live 系统似乎运行没有问题。

仅当在已安装的 Linux 上仅创建一个用户时，该脚本才有效，因为 squashfs 不支持 ACL，但目录 /media/username/ 需要 ACL。

这是脚本：

    #!/bin/bash
    
    # Destination directory:
    DEST=$HOME/squashfs
    
    sudo mkdir -p ${DEST}
    
    # Copying installation in destination directory:
    sudo rsync --progress --specials --perms -av -lXEog --delete / ${DEST} --one-file-system \
    --exclude=/proc/* --exclude=/tmp/* --exclude=/dev/* \
    --exclude=/sys/* --exclude=/boot/* \
    --exclude=/etc/mtab --exclude=${DEST}
    
    # Make /media/username ownership to the user, because squashfs doesn't support ACL
    MEDIA="$USER:$USER $DEST/media/$USER"
    sudo chown $MEDIA
    
    # Remove links to mounted drives in destination directory /media/username/:
    MEDIA="$DEST/media/$USER"
    sudo rm -f $MEDIA/*
    
    # Remove unwanted entries in fstab of the future live system: 
    sudo sed -i '/\/boot\/efi/d' ${DEST}/etc/fstab 
    sudo sed -i '/swap/d' ${DEST}/etc/fstab 
    sudo sed -i '/UUID=.*\ \/\ /d' ${DEST}/etc/fstab
    
    # Mount special files in order to chroot:
    sudo mount -o bind /proc ${DEST}/proc
    sudo mount -o bind /dev ${DEST}/dev
    sudo mount -o bind /dev/pts ${DEST}/dev/pts
    sudo mount -o bind /sys ${DEST}/sys
    sudo cp /etc/resolv.conf ${DEST}/etc/resolve.conf
    
    # upgrade the chrooted system, and install live-boot package 
    # as well as the lastest kernel: 
    sudo chroot ${DEST} apt-get update
    sudo chroot ${DEST} apt-get upgrade
    sudo chroot ${DEST} apt-get remove linux-image*
    sudo chroot ${DEST} apt-get install live-boot
    sudo chroot ${DEST} apt-get install linux-image-amd64
    sudo chroot ${DEST} apt-get clean
    sudo chroot ${DEST} apt clean
    
    # Umount the special files:
    sudo umount ${DEST}/proc
    sudo umount ${DEST}/dev/pts
    sudo umount ${DEST}/dev
    sudo umount ${DEST}/sys
    
    # Delete unwanted files:
    [ -n "$DEST" ] && sudo find ${DEST}/var/mail ${DEST}/var/lock ${DEST}/var/backups ${DEST}/var/tmp -type f -exec rm {} \;

    # Delete only OLD log files:
    [ -n "$DEST" ] && sudo find ${DEST}/var/log -type f -iregex '.*\.[0-9].*' -exec rm -v {} \;
    [ -n "$DEST" ] && sudo find ${DEST}/var/log -type f -iname '*.gz' -exec rm -v {} \;
    
    # Clean current log files:
    [ -n "$DEST" ] && sudo find ${DEST}/var/log -type f | while read file; do echo -n '' | sudo tee $file; done
    
    # Clean Pakcage cache:
    [ -n "$DEST" ] && sudo rm -v ${DEST}/var/cache/apt/archives/*.deb
    
    # Remove old kernel and initrd in the partition where will be installed the live system: 
    sudo rm -f /media/$USER/LIVE/live/initrd.img*
    sudo rm -f /media/$USER/LIVE/live/vmlinuz*    
    
    # Copy new kernel and initrd in the partition where will be installed the live system: 
    sudo mv -f ${DEST}/boot/initrd.img* /media/$USER/LIVE/live/initrd.img
    sudo mv -f ${DEST}/boot/vmlinuz* /media/$USER/LIVE/live/vmlinuz
    
    # Remove old shquashfs in the partition where will be installed the live system: 
    sudo rm -f /media/$USER/LIVE/live/filesystem.squashfs
    
    # Make the new squashfs:
    sudo mksquashfs ${DEST} /media/$USER/LIVE/live/filesystem.squashfs -xattrs -processors 4 -noappend -always-use-fragments

`/media/$USER/LIVE/` is where the live system partition is mounted.
   
Then I boot the live system placed on a partition with the kernel options: `toram boot=live`

编辑：

当我运行df命令时，它告诉我/dev/shm已安装在/run/live/medium.

该命令mount | grep medium告诉我它/dev/shm也安装在/usr/lib/live/mount/medium.

系统似乎在 RAM 中保存了一个包含 squashfs 的分区的副本。

当我想卸载时/run/live/medium，它告诉我这是不可能的，因为the target is active。但我已经成功卸载了/usr/lib/live/mount/medium。

所以我想知道这些问题是否有联系，是否有办法卸载/run/live/medium？