IBM DB2 database quick reference.
Discover DB2 instances
Default instance is db2inst1.
Using Ncat
sudo ncat -nv --source-port 53 $IP 50000
Using Metasploit
See Metasploit.
msfconsole
search db2
use auxiliary/scanner/db2/db2_version
show options
SET RPORT 50000
set RHOSTS x.x.x.x
set DATABASE toolsdb
Using Nmap NSE

Nmap NSE on DB2 are only for the IBM DB2 Administration Server (DAS) on TCP or UDP port 523.
ls -la /usr/share/nmap/scripts/*db2*
/usr/share/nmap/scripts/broadcast-db2-discover.nse
/usr/share/nmap/scripts/db2-das-info.nse
Install the DB2 client

When possible, use SQuirreL instead!! And download db2 jdbc driver.
# Install IBM Data Server Runtime Client
# Unzip the installer
cd rtcl
./db2setup -f sysreq
# A window will open
Click Next
Directory /opt/ibm/db2/V11.5
Typical
Uncheck Create instance
Check I agree to the IBM terms
Click Next
Click Finish
Click on Post-installation Steps
# Run the validation tool
/opt/ibm/db2/V11.5/bin/db2val
export PATH="$PATH:/opt/ibm/db2/V11.5/bin"
Connect to database instance using the DB2 client
###export DB2INSTANCE=DB2_01
db2cli
db2 => CONNECT TO myIP:myPort/myDB USER myid01 USING mypw01
Default Users & Passwords
db2inst1/db2inst1
db2inst2/db2inst2
db2admin/db2admin
#-------------------------------------------------------------------------------
# Configurations / Parameters
#-------------------------------------------------------------------------------
# Configuration file
# Start
# Stop
# Execute OS commands from within client
#-------------------------------------------------------------------------------
# Default Users / Passwords
#-------------------------------------------------------------------------------
In /usr/share/metasploit-framework/data/wordlists/db2_default_pass.txt
SQL Injection
http://db2guideonline.blogspot.com/2014/09/example-sql-injection-in-db2-how-to.html