#!/bin/bash

cat /etc/*release                                               # find Linux distribution version
cat /etc/*-release | uniq -u | grep 'release'                   # show Linux release
sudo fuser -k 80/tcp                                            # kill all processes using port 80 (useful if nginx won't stop/restart gracefully)
alias cdwww="cd /var/www/html/"                                 # add to ~/.bashrc for shortcut to webroot

# ansible
ansible-playbook <playbook>.yml --private-key ~/.ssh/<key>.pem	# specify a private key to use to connect when running playbooks on EC2 instances

# apt
apt list --installed                                            # list all installed packages
apt-cache policy |grep http |awk '{print $2 $3}' |sort -u       # list apt sources
apt-get install <package name>=<version>                        # install a specific version of a package

# AWS motd banner
sudo vim /etc/update-motd.d/30-banner                           # edit motd banner on AWS Amazon Linux AMI systems
sudo /usr/sbin/update-motd                                      # update motd banner from contents of /etc/update-motd.d/ on AWS Amazon Linux AMI systems

# cron
  sudo crontab -l -u <user>                                     # view cron jobs for a specific user
  sudo crontab -e -u <user>                                     # edit cron jobs for a specific user
  sudo sh -c 'tail -n +1 /var/spool/cron/*'                     # list crontab for all users
# cron time string format:
  * * * * *                                                     # cron time string character positions
  └─│─│─│─│── minute                                            # run cron job (0-59) minutes past the hour, or * for every minute
    └─│─│─│── hour                                              # run cron job (0-23) hours past midnight, or * for every hour
      └─│─│── day of month                                      # run cron job on day (1-31) of the month, or * for every day
        └─│── month                                             # run cron job during month (1-12) of the year, or * for every month
          └── day of week                                       # run cron job every (0-6) days past Sunday, or * for every day of the week
# cron time special characters:
  * (asterisk)                                                  # cron time: any/every
  , (comma)                                                     # cron time: value list separator
  - (hyphen)                                                    # cron time: defines range of values
  / (forward slash)                                             # cron time: step value
# cron time examples:
  * * * * *                                                     # run cron job every minute
  0 0-6,18-23 * * *                                             # run cron job hourly from 18:00 through 06:00
  10 */2 * * *                                                  # run cron job 10 minutes past the hour, every other hour
# See http://crontab.guru for more interactive cron examples

# docker
docker --version						# check Docker version
docker images							# list Docker images
docker search							# search the Docker Hub for images
docker pull <image>						# pull an image or a repository from Docker Hub or another registry
docker create <image>						# create a writeable container from an image and prepare it to run
docker run <image>						# creates container from an image and runs it (similar to docker create + docker start)
docker run -it centos:latest /bin/bash				# run a CentOS container, start bash and attach to to terminal
docker run -d centos:latest /bin/bash				# run a CentOS container in detached mode
docker start <container>					# start a stopped container
docker inspect <image or container>				# show low-level information on Docker objects
docker exec <container> <command>				# pass command to running container
docker exec -it <container> /bin/bash				# start a bash prompt in a running container and attach it to terminal 
docker stop <container name>					# stop a running container
docker ps							# list running containers
docker ps -a							# list all containers, running or stopped
docker rm <container>						# remove container
docker rm `docker ps -a -q`					# remove all containers
docker rmi <image>						# remove image
docker rmi -f <image>						# remove image (force)

# git
git init								    # initialize empty git repo in .git/
git status								    # show current branch, list changes to be committed, untracked files, etc.
git add <file>								    # add untracked file to staging area
git add '*.txt'								    # add all new .txt files to staging area
git --git-dir=/my/path/.git/ --work-tree=/my/path/ add <file>		    # add file in another directory to staging area
git commit -m "<message>"						    # store staged changes
git --git-dir=/my/path/.git/ --work-tree=/my/path/ commit -m "<comment>"    # commit changes in another directory
git log									    # list changes committed so far
git remote add origin <https://some.repo.com>				    # add remote repository
git push -u origin master						    # push local changes to remote repo origin (-u stores params so only 'git push' is needed next time) 
git pull origin master							    # check for changes on remote origin repo and pull them down
git diff HEAD								    # check what is different from most recent commit
git diff --staged							    # show changes within files that have already been staged
git reset <file>							    # unstage <file>
git branch								    # show branches and highlight which branch is currently being used
git branch <branch>							    # create branch called <branch>
git branch -d <branch>							    # delete <branch> branch
git checkout -- <file>							    # get rid of changes since last commit for <file>
git checkout <branch>							    # switch to branch <branch>
git checkout -b <branch>						    # create and switch to branch <branch>
git rm '*.txt'								    # deletes .txt files from disk and stages removal of the files in the repo
git merge <branch>							    # merge changes from <branch> branch into current branch
git clone <repo> .							    # clone repository in current local directory

# grep
grep -rli --exclude-dir={dir1,dir2,dir3} keyword /search/path   # search path for pattern with exceptions
grep "^[^#;]" file.name                                         # show only non-commented lines (ignore comments)
grep '^[[:blank:]]*[^[:blank:]#;]' file.name                    # show only non-commented non-blank lines (ignore comments and blank lines)

# history (bash)
HISTCONTROL=ignorespace                                         # tell bash not to record commands starting with space to history (add to .bashrc to make persistent)
history -d <number>                                             # delete command <number> from bash history

# ln
ln -s <target> <name>						# creates a symbolic link (symlink) to <target> called <name>

# magento
php bin/magento admin:user:create --admin-user='<user>' --admin-password='<password>' --admin-email='<user@email.com>' --admin-firstname='<first>' --admin-lastname='<last>'    # create admin user
rm -rf var/di/* var/generation/* var/cache/* var/log/* var/page_cache/* var/session/* var/view_preprocessed/* pub/static/*  # clear out magento cache and temp directories
magento setup:install                                           # install Magento software
magento setup:upgrade                                           # update the Magento software
magento setup:di:compile                                        # run single-tenant compiler
magento setup:static-content:deploy                             # deploy static content
magento cache:clean                                             # clean cache type(s)
magento cache:flush                                             # flush cache storage used by cache type(s)
magento module:{enable|disable}                                 # enable or disable modules
magento setup:db:status                                         # check if the database is up-to-date with the code
export PATH=$PATH:/var/www/html/bin                             # add to ~/.bashrc to add magento commands to $PATH

# mysql
mysql -u db_username -p db_name < db_file.sql                   # import database 'db_name' from 'db_file.sql' into mysql (use gunzip if file.sql.gz)
SELECT User FROM mysql.user;                                    # mysql > show all database users
SHOW DATABASES;                                                 # mysql > show all databases
sed -e 's/DEFINER[ ]*=[ ]*[^*]*\*/\*/' file.sql > newfile.sql   # make a mysql dump ready to import without SUPER permissions error
# dump mysql database 'db_name' on server 'db_server' to file:
mysqldump -h <db_server> -u <db_username> -p <db_name> --single-transaction | sed -e 's/DEFINER[ ]*=[ ]*[^*]*\*/\*/' | gzip > <db_file>.sql.gz

# netstat
sudo netstat -tulpn | grep :80                                  # find out what is running/listening on port 80
sudo netstat | grep http | wc -l                                # check how many http connections are open

# nginx
sudo nginx -s reload                                            # reload nginx config
sudo nginx -s quit                                              # gracefully shutdown nginx
sudo nginx -s stop                                              # terminates nginx process
sudo nginx -t                                                   # nginx config syntax check (pre-load)
sudo nginx -T                                                   # displays currently running configs
sudo nginx -v                                                   # checks nginx version
ps aux | grep "[n]ginx"                                         # check running nginx processes
service nginx status                                            # check nginx service status

# rsync
rsync -havz --stats --progress -e "ssh -i /path/to/sshkey.pem" /path/to/local/file user@remotehost:~/   # transfer local file to home directory on remote server
rsync -havz --stats --progress -e "ssh -i /path/to/sshkey.pem" user@remotehost:~/file ~/                # transfer file from home directory on remote server to local home directory

# screen
screen                                                          # start screen
<ctrl-a> c                                                      # creat new screen window
<ctrl-a> n                                                      # go to next screen window
<ctrl-a> p                                                      # go to previous screen window
<ctrl-a> "						"	# show list of screen windows (allows you to select a window to change to)
<ctrl-a> w                                                      # show screen window bar
<ctrl-a> m                                                      # monitor current screen window for activity, alert when active
<ctrl-a> _                                                      # monitor current screen window for silence or no activity, alert when inactive
<ctrl-a> d                                                      # detach from current screen
screen -ls                                                      # list screen sessions
screen -r [pid.session.name]                                    # re-attach to screen session
https://www.howtoforge.com/linux_screen                         # decent screen tutorial

# ssh
ssh-keygen -t rsa										# generate ssh keys
find ~/.ssh -type f -exec chmod -R 600 {} \; && find ~/.ssh -type d -exec chmod -R 700 {} \;	# fix permissions on ssh folder and keys
ssh-keygen -R hostname										# remove a host from known_hosts file

# tar
tar xvzf file.tar.gz                                            # extract entire .tar.gz archive
tar tvf file.tar.gz                                             # view a table of contents by listing all files in achieve
tar xvjf file.tar.bz2                                           # extract file which was compressed using a bZip2 compressor
tar zcvf archive-name.tar.gz directory-name                     # compress entire directory

# tmux
tmux new -s session_name					# creates a new tmux session named session_name
tmux attach -t session_name					# attaches to an existing tmux session named session_name
tmux switch -t session_name					# switches to an existing session named session_name
tmux list-sessions						# lists existing tmux sessions
tmux kill-session -t :0-9					# kill tmux session
tmux detach							# detach the currently attached session
tmux new-window							# create a new window
tmux select-window -t :0-9					# move to the window based on index
tmux rename-window						# rename the current window
tmux split-window						# splits the window into two vertical panes
tmux split-window -h						# splits the window into two horizontal panes
tmux swap-pane -[UDLR]						# swaps pane with another in the specified direction
tmux select-pane -t :.+						# selects the next pane in numerical order
tmux list-keys							# lists out every bound key and the tmux command it runs
tmux list-commands						# lists out every tmux command and its arguments
tmux info							# lists out every session, window, pane, its pid, etc.
tmux source-file ~/.tmux.conf					# reloads the current tmux configuration (based on a default tmux config)
  # tmux shortcuts:
  <ctrl-b> d							# tmux detach
  <ctrl-b> c							# tmux new-window
  <ctrl-b> 0-9							# tmux select-window
  <ctrl-b> ,							# tmux rename-window
  <ctrl-b> "						"	# tmux split-window
  <ctrl-b> %							# tmux split-window -h
  <ctrl-b> { or }						# tmux swap-pane -[UDLR]
  # tmux crash course:
  https://robots.thoughtbot.com/a-tmux-crash-course

# user and group management
useradd -s /sbin/nologin dbuser                                 # add a user without a valid login shell (to establish SSH tunnels for DB access, for example)
groups <user>                                                   # list groups <user> is in
sudo usermod -a -G <group> <user>                               # add user to group

# varnish
varnishlog -g request -q 'ReqMethod eq "PURGE"'                 # view logged varnish purge requsts

# yum
yum list all                                                    # list all installed and available packages
yum list installed                                              # list all installed packages
yum list available                                              # list all available packages
yum repolist all                                                # list all yum repositories and their status
yum repolist enabled                                            # list only enabled yum repositories
yum repolist disabled                                           # list disabled yum repositories
yum --disablerepo=* --enablerepo=repo_name install [packages]   # only install packages from the 'repo_name' repository

# zip, gzip
gunzip file.gz                                                  # extract .gz file without tar
gzcat <filename>                                                # look at gzipped file contents without extracting it