Update: There is a complete github project now https://github.com/theodorosploumis/drush-installer.
Assuming that you have ssh access to the server and no sudo permissions.
Also, there must be
zip installed. Otherwise you have to change the related commands according to your tools.
Drush now is installed through Composer so we need to install Composer before Drush.
# 1. Login to the server from your local machine with ssh
$ ssh USER@SERVER
$ cd ~
# 2. Use Bash as command line (if you like you can use your own CL too!)
$ chsh -s $(which bash) $USER
# 3. Install Composer
$ mkdir ~/bin
$ curl -sS https://getcomposer.org/installer | php -- --install-dir=bin
# 4. Download Drush files (we are in our home folder)
# 4.1 Git method (recommended). After this go to step 5
$ cd ~
$ git clone firstname.lastname@example.org/drush-ops/drush.git
$ cd drush
$ git checkout 6.x
# 4.2 Alternatively, if you don't have git,
# download the files with wget. Currently stable version is 6.x
# Notice that you need Drush 7.x to be able to work with Drupal 8.x
$ wget https://github.com/drush-ops/drush/archive/6.x.zip
# Unzip it and rename the folder to /drush
$ unzip 6.x.zip
$ rm 6.x.zip
$ mv ~/drush-6.x ~/drush
# 5. Make the drush folder executable by current USER
$ chmod u+x ~/drush/drush
# 6. Install Drush from Composer
$ cd ~/drush
$ php ~/bin/composer.phar install
# 7. Add alias drush to .bash_profile
$ echo "alias drush='~/drush/drush'" > ~/.bash_profile
# 8. Source the changed .bash_profile or restart ssh session
$ source ~/.bash_profile
I have created 2 simple bash scripts for this task.