root@armadillo:~# cat /etc/mtab
/dev/root / ext4 rw,relatime,data=ordered 0 0
sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
devtmpfs /dev devtmpfs rw,nosuid,size=247028k,nr_inodes=61757,mode=755 0 0
securityfs /sys/kernel/security securityfs rw,nosuid,nodev,noexec,relatime 0 0
tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0
tmpfs /run tmpfs rw,nosuid,nodev,mode=755 0 0
tmpfs /run/lock tmpfs rw,nosuid,nodev,noexec,relatime,size=5120k 0 0
tmpfs /sys/fs/cgroup tmpfs ro,nosuid,nodev,noexec,mode=755 0 0
cgroup /sys/fs/cgroup/systemd cgroup rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd 0 0
cgroup /sys/fs/cgroup/devices cgroup rw,nosuid,nodev,noexec,relatime,devices 0 0
cgroup /sys/fs/cgroup/pids cgroup rw,nosuid,nodev,noexec,relatime,pids 0 0
cgroup /sys/fs/cgroup/memory cgroup rw,nosuid,nodev,noexec,relatime,memory 0 0
cgroup /sys/fs/cgroup/rdma cgroup rw,nosuid,nodev,noexec,relatime,rdma 0 0
cgroup /sys/fs/cgroup/cpu,cpuacct cgroup rw,nosuid,nodev,noexec,relatime,cpu,cpuacct 0 0
cgroup /sys/fs/cgroup/freezer cgroup rw,nosuid,nodev,noexec,relatime,freezer 0 0
cgroup /sys/fs/cgroup/blkio cgroup rw,nosuid,nodev,noexec,relatime,blkio 0 0
/dev/mmcblk0gp0 /opt/license squashfs ro,relatime 0 0
tmpfs /run/user/0 tmpfs rw,nosuid,nodev,relatime,size=51144k,mode=700 0 0

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root@armadillo:~# ls -l /mnt/usb
total 0

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root@armadillo:/etc/udev/rules.d# df -a
Filesystem      1K-blocks   Used Available Use% Mounted on
/dev/root         3424176 565824   2664696  18% /
sysfs                   0      0         0    - /sys
proc                    0      0         0    - /proc
devtmpfs           247028      0    247028   0% /dev
securityfs              0      0         0    - /sys/kernel/security
tmpfs              255732      0    255732   0% /dev/shm
devpts                  0      0         0    - /dev/pts
tmpfs              255732   3424    252308   2% /run
tmpfs                5120      0      5120   0% /run/lock
tmpfs              255732      0    255732   0% /sys/fs/cgroup
cgroup                  0      0         0    - /sys/fs/cgroup/systemd
cgroup                  0      0         0    - /sys/fs/cgroup/devices
cgroup                  0      0         0    - /sys/fs/cgroup/pids
cgroup                  0      0         0    - /sys/fs/cgroup/memory
cgroup                  0      0         0    - /sys/fs/cgroup/rdma
cgroup                  0      0         0    - /sys/fs/cgroup/cpu,cpuacct
cgroup                  0      0         0    - /sys/fs/cgroup/freezer
cgroup                  0      0         0    - /sys/fs/cgroup/blkio
/dev/mmcblk0gp0       128    128         0 100% /opt/license
tmpfs               51144      0     51144   0% /run/user/0

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root@armadillo:/etc/udev/rules.d# df /mnt/usb
Filesystem     1K-blocks   Used Available Use% Mounted on
/dev/root        3424176 565824   2664696  18% /