I have run Ghost for quite some time now and I have been through two upgrade process so I think it will be a good idea to save a procedure for easy upgrading. I found the instruction here.

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###Manually upgrade Ghost

I usually use manual upgrade method because I don’t inspect the automatic scripts yet if it is compatible with my installation.

# cd /var/www/html/ghost
# mkdir temp
# cd temp/
# curl -L -O https://ghost.org/zip/ghost-latest.zip
# unzip ghost-latest.zip
# cd ..
# cp temp/*.md temp/*.js temp/*.json .
# rm -R core
# cp -R temp/core .
# cp -R temp/content/themes/casper content/themes
# npm install --production
# rm -R temp
# su ghost -c /var/www/html/ghost/starter.sh -s /bin/sh

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###Reference http://www.howtoinstallghost.com/how-to-update-ghost/