Increase Bash history size

vi /root/.bashrc

Add:
export HISTSIZE=100000
export HISTFILESIZE=10000

When saved run:
source ~/.bashrc

Example of my bashrc file:

export PS1='\[\033[01;31m\]\u\[\033[01;33m\]@\[\033[01;32m\]\h \[\033[01;33m\]\w \[\033[01;35m\]\$ \[\033[00m\]'
umask 022

export LS_OPTIONS='--color=auto -h'
eval "`dircolors`"

# .bashrc

# User specific aliases and functions

alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'

# Bas
export HISTSIZE=100000
export HISTFILESIZE=10000
export GOPATH=~/go
export PATH=$PATH:$GOPATH/bin

alias nload='nload -u H -U H'

# Source global definitions
if [ -f /etc/bashrc ]; then
        . /etc/bashrc
fi