tmux 2.0 and tmux 2.3 installation steps for Ubuntu. Or build from tmux source v2.5 for Ubuntu and CentOS.

tmux__CentOS__build_from_source.sh

# Steps to build and install tmux from source.
# Takes < 25 seconds on EC2 env [even on a low-end config instance].

VERSION=2.7
sudo yum -y remove tmux
sudo yum -y install wget tar libevent-devel ncurses-devel
wget https://github.com/tmux/tmux/releases/download/${VERSION}/tmux-${VERSION}.tar.gz
tar xzf tmux-${VERSION}.tar.gz
rm -f tmux-${VERSION}.tar.gz
cd tmux-${VERSION}
./configure
sudo make install
cd -
sudo rm -rf /usr/local/src/tmux-*
sudo mv tmux-${VERSION} /usr/local/src

## Logout and login to the shell again and run.
## tmux -V

tmux__Ubuntu__build_from_source.sh

# Steps to build and install tmux from source on Ubuntu.
# Takes < 25 seconds on EC2 env [even on a low-end config instance].
VERSION=2.7
sudo apt-get -y remove tmux
sudo apt-get -y install wget tar libevent-dev libncurses-dev
wget https://github.com/tmux/tmux/releases/download/${VERSION}/tmux-${VERSION}.tar.gz
tar xf tmux-${VERSION}.tar.gz
rm -f tmux-${VERSION}.tar.gz
cd tmux-${VERSION}
./configure
make
sudo make install
cd -
sudo rm -rf /usr/local/src/tmux-*
sudo mv tmux-${VERSION} /usr/local/src

## Logout and login to the shell again and run.
## tmux -V

tmux_install.sh

##########################################################################################
##### Please check the installation from source, which is easy and fast.
##########################################################################################
# tmux v2.3 installation steps for Ubuntu [various OS versions]
sudo apt-get update -yqqu
sudo add-apt-repository -yu ppa:pi-rho/dev
sudo apt-get update -yqqu
sudo apt-get install -yqqu python-software-properties software-properties-common
sudo apt-get install -yqq tmux-next=2.3~20160913~bzr3547+20-1ubuntu1~ppa0~ubuntu16.04.1
# sudo apt-get install -yqq tmux-next=2.3~20160913~bzr3547+20-1ubuntu1~ppa0~ubuntu15.10.1
# sudo apt-get install -yqq tmux-next=2.3~20160913~bzr3547+20-1ubuntu1~ppa0~ubuntu15.04.1
# sudo apt-get install -yqq tmux-next=2.3~20160913~bzr3547+20-1ubuntu1~ppa0~ubuntu14.04.1
# sudo apt-get install -yqq tmux-next=2.3~20160913~bzr3547+20-1ubuntu1~ppa0~ubuntu12.04.1
tmux-next -V

# tmux v2.0 installation steps for Ubuntu 14.04 (Trusty Tahr)
tmux -V
sudo apt-get update -yqqu
sudo apt-get install -yqqu python-software-properties software-properties-common
sudo add-apt-repository -yu ppa:pi-rho/dev
sudo apt-get update -yqqu
sudo apt-get install -yqqu tmux
# sudo apt-get install -yqqu tmux=2.0-1~ppa1~t
tmux -V

# tmux v1.9 installation steps for Ubuntu 14.04 (Trusty Tahr)
sudo apt-get update -yqqu
sudo apt-get install -yqqu python-software-properties software-properties-common
sudo add-apt-repository -yu ppa:pi-rho/dev
sudo apt-get update -yqqu
sudo apt-get install -yqqu tmux=1.9a-1~ppa1~t
tmux -V

# On Ubuntu 12.04 (Precise Pangolin), step 5 would be: sudo apt-get install -y tmux=1.9a-1~ppa1~p
# On Ubuntu 13.10 (Saucy Salamander), step 5 would be: sudo apt-get install -y tmux=1.9a-1~ppa1~s

run one at a time.
sudo add-apt-repository ppa:pi-rho/dev
sudo apt-get update
sudo apt-get install tmux-next=2.3~20161124~bzr3624+20-1ubuntu1~ppa0~ubuntu16.04.1

Or just use plain "tmux-next" as in sudo apt-get install tmux-next

For the latest version available in the launchpad repo, go to https://launchpad.net/~pi-rho/+archive/ubuntu/dev and look for the package name on the list for your Ubuntu release. It seems the latest "tmux-next" package as of writing of this message is actually version 2.4 even though the string for it is: 2.3~20170107~bzr3641+20-1ubuntu1~ppa0~ubuntu16.04.1

I ran this command to install:

sudo apt-get install tmux-next=2.320170128bzr3691+20-1ubuntu1ppa0ubuntu14.04.1

The command "tmux-next -V" produced this as output:

tmux-next master

I assume this is not the correct output value, so is there another method to determine the actual version number?
I am a total newbie to tmux.

@GoodGuy98 Same issue here

When run for 'Ubuntu various versions', I get the following error:
E: Version '2.320160913bzr3547+20-1ubuntu1ppa0ubuntu16.04.1' for 'tmux-next' was not found

currently, you must replace
2.320160913bzr3547+20-1ubuntu1ppa0ubuntu16.04.1
with:
2.320170419bzr3777+20-1ubuntu1ppa0ubuntu16.04.1

following the install from source worked on Ubuntu 16.04

Thanks!

having trouble to configure $PWD to start on the new session while splitting on version 2.5 anyone?

Thanks :)

Thank you for CentOS steps!