Weird "AT%IPSYS?" and "AT+CGMR" when playing with ESP8266

These few days when i am playing with my ESP8266 on Ubuntu, using a PIC32 MIPS configured as USB UART pass-through (USB UART Tx => EPS8266 Rx, and vice versa).

The problem appeared when i reset my development board, there are some weird AT commands sent out to the ESP8266 which is not programmed in my PIC32. I have also not typed any AT commands on minicom (or screen) terminal and these AT commands just came out from nowhere.

Here is some of the possible weird AT commands that sent out to my serial port (and hence to ESP8266):

AT%IPSYS?
AT+CGMR
AT

After some searching on the internet, i have found a bug report (and it's the only search result related on Google) regarding "AT%IPSYS?" on "ModemManager". At this point, I knew that weird output command were coming out from my Ubuntu!

I think the reasons of the existence of the problem might be "ModemManager" thinks my serial port, which literally connected directly to ESP8266 is an AT modem. It also responds to the "AT" command which returns "OK\r\n" afterwards. After removing "ModemManager" from my Ubuntu machine by issuing:

sudo apt-get purge modemmanager

, this issue had gone away!