How to configure Cisco device in Linux machine with Minicom? You need installed Minicom utility, C-13 power cable, physical connection from your PC to Cisco device via COM-to-USB cable like this:

Minicom utility need for connecting and sending commands to devices, connected by serial port, based on RS-232 standard and have out-of-box drivers. As an alternative in Windows may be used PuTTY.

If you not have already installed Minicom, this command help you:

sudo apt install minicom -y

Ok, after device is connected determine port in Debian-based systems:

sudo dmesg | grep -i tty

The output will look something like one of these:

[    0.788856] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
[    0.789144] 00:08: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
[94023.461242] usb 2-1: pl2303 converter now attached to ttyUSB0
[107561.131086] type=1503 audit(1260922689.994:33): operation="open" pid=27195 parent=27185 profile="/usr/sbin/cupsd" requested_mask="w::" denied_mask="w::" fsuid=0 ouid=0 name="/dev/ttyUSB0

Launch new terminal window and start minicom application:

sudo minicom -s

Select Serial port setup.
In opened window press A button on keyboard for set Serial Device and enter value: /dev/ttyUSB0.
Press E button for change baud rate, then press C to set it to 9600.
Change Hardware Flow Control to No by pressing F.
Select Exit menu item.

Now in front of you opening Cisco's unpriveleged mode. Set password for enable mode:

cisco> enable
cisco# configure terminal
cisco(config)# enable password my_password

Set username and password for configure terminal mode:

cisco> enable
cisco# configure terminal
cisco(config)# username <username> password <password> privilege 15

Set authentication method:

cisco> enable
cisco# configure terminal
cisco(config)# aaa authentication serial console LOCAL

Exit from Minicom with saving changes. Press <CTRL+A> keyboard shortcut, then X button, then Enter.