Some tips about ubuntu server | or it may works on other linux distributions too

Mount usb-hdd/usb-flash disk to Ubuntu Server:

1, plug the hardware

2, run below command, see which maybe the device name

tail -f /var/log/messages

3, mount it

sudo mount -t <file system type|vfat> <device name|/dev/sdb2> <path to mount|/mnt>

Install Linux header files (maybe for vmware server):

1, run

uname -r

2, run

sudo apt-get install linux-headers-<output from the last command>

Removed your only account out of sodoers:

1, reboot machine.

2, press esc when grub loading

3, select "recovery mode (single root)" mode

4, run

usermod -g admin <username>

5, exit