极路由扩容 2--mount 失败

我有个外接硬盘

可以在极路由里面

cp /* /someMountDeviceDir mount /mnt/xxx / 这样子,扩容吗?会有什么后果,可能有知识遗漏的太多...

我看了下 /etc/fstab 文件是空的,没有挂载信息

来求教下,谢谢

    root@Hiwifi:~# mount
    rootfs on / type rootfs (rw)
    /dev/root on /rom type squashfs (ro,relatime)
    ubi0:overlay on /overlay type ubifs (rw,relatime)
    overlayfs:/overlay on / type overlayfs (rw,noatime,lowerdir=/,upperdir=/overlay)
    /dev/sda1 on /tmp/storage/sda1 type vfat (rw,dirsync,nosuid,nodev,noatime,nodiratime,fmask=0000,dmask=0000,allow_utime=0022,codepage=437,iocharset=utf8,shortname=mixed,errors=remount-ro)
    /dev/sda2 on /tmp/storage/sda2 type exfat (rw,dirsync,nosuid,nodev,noatime,nodiratime,fmask=0000,dmask=0000,allow_utime=0022,iocharset=utf8,namecase=0,errors=remount-ro)

    root@Hiwifi:~# mount -t exfat /dev/sda2 /mnt

    root@Hiwifi:~# df -h
    Filesystem                Size      Used Available Use% Mounted on
    rootfs                   10.3M      1.9M      7.8M  20% /
    /dev/root                11.3M     11.3M         0 100% /rom
    ubi0:overlay             10.3M      1.9M      7.8M  20% /overlay
    overlayfs:/overlay       10.3M      1.9M      7.8M  20% /
    tmpfs                   524.3K         0    524.3K   0% /dev
    ubi1:opt                 35.5M     20.5K     33.6M   0% /tmp/cryptdata
    tmpfs                   130.5M      2.8M    127.7M   2% /plugins/tmp
    ubi1:opt                 35.5M     20.5K     33.6M   0% /plugins/crypt
    /dev/sda1               206.5M       512    206.5M   0% /tmp/storage/sda1
    /dev/sda2               999.9G     11.3M    999.9G   0% /tmp/storage/sda2
    /dev/sda2               999.9G     11.3M    999.9G   0% /mnt

    root@Hiwifi:~# mkdir /mnt/workdir

    root@Hiwifi:~# mount -t overlay overlayfs:/mnt -olowerdir=/,upperdir=/mnt,workdir=/mnt/workdir /

    mount: mounting overlayfs:/mnt on / failed: No such device

    root@Hiwifi:~# mount -t overlay /mnt -olowerdir=/,upperdir=/mnt,workdir=/mnt/workdir / 

    mount: mounting /mnt on / failed: No such device 

    root@Hiwifi:~# mount -t overlay /dev/sda2 -olowerdir=/,upperdir=/mnt,workdir=/mnt/workdir / 

    mount: mounting /dev/sda2 on / failed: No such device

上面写的, overlay 挂载方式,错在哪里了

谢谢大家