brianz · August 11, 2016 04:35 · Aug 11, 2016 · Aug 2, 2016 · Aug 2, 2016 · Aug 2, 2016
diff --git a/tech-scratch-pad.md b/tech-scratch-pad.md
@@ -9,6 +9,11 @@ linux: netstat -lnptu
 mac: netstat -a -p tcp
 ```
 
+## Find what is listening on a port
+
+```
+lsof -Pnl +M -i4
+```
 ## Reset postgres pkey sequences
 
 ```

diff --git a/tech-scratch-pad.md b/tech-scratch-pad.md
@@ -35,10 +35,11 @@ scutil --dns
 find . -name '*.py' -exec sed -i '' -e  "s/OLD_PATTERN/NEW_PATTERN/g" {} \;
 ```
 
-## Add a user into an existing group
+## Add/remove users into/out of groups
 
 ```
 usermod -a -G GROUP_NAME USER_NAME
+usermod -G "" USER_NAME
 ```
 
 ## Read an SSL certificate

diff --git a/tech-scratch-pad.md b/tech-scratch-pad.md
@@ -35,6 +35,12 @@ scutil --dns
 find . -name '*.py' -exec sed -i '' -e  "s/OLD_PATTERN/NEW_PATTERN/g" {} \;
 ```
 
+## Add a user into an existing group
+
+```
+usermod -a -G GROUP_NAME USER_NAME
+```
+
 ## Read an SSL certificate
 
 ```

diff --git a/tech-scratch-pad.md b/tech-scratch-pad.md
@@ -4,8 +4,10 @@
 
 ## List open ports
 
+```
 linux: netstat -lnptu
 mac: netstat -a -p tcp
+```
 
 ## Reset postgres pkey sequences
 

diff --git a/tech-scratch-pad.md b/tech-scratch-pad.md
@@ -0,0 +1,174 @@
+## Sum column using awk
+
+`cat count.txt | awk '{sum+=$1} END {print sum}'`
+
+## List open ports
+
+linux: netstat -lnptu
+mac: netstat -a -p tcp
+
+## Reset postgres pkey sequences
+
+```
+SELECT pg_catalog.setval(pg_get_serial_sequence('TABLE_NAME', 'id'), (SELECT MAX(id) FROM TABLE_NAME)+1);
+```
+
+## List connected hosts
+
+```
+netstat -n -A inet
+netstat -n -A inet | awk '{print $5}' | tr ':' ' ' | awk '{print $1}' | sort | uniq -c
+```
+
+## DNS Stuff
+
+```
+dscacheutil -q host -a name admin.ccdev.vg
+scutil --dns
+```
+
+## In-place replacement
+
+```
+find . -name '*.py' -exec sed -i '' -e  "s/OLD_PATTERN/NEW_PATTERN/g" {} \;
+```
+
+## Read an SSL certificate
+
+```
+openssl x509 -in public.pem -text -noout
+```
+
+## Execute a command for a user who has no login shell
+
+```
+su -s /bin/bash -c '/path/to/your/script' testuser
+```
+
+## Remove virtual box virtual interfaces
+
+```
+VBoxManage hostonlyif remove vboxnet1
+```
+
+## Purge all queues from rabbitmq
+
+```
+for q in ` sudo rabbitmqctl list_queues | awk '{print $1'} | egrep "d16|celery"`;
+     do celery amqp queue.purge $q;
+done
+```
+
+## Display status of loaded kernel extensions
+
+```
+man kextstat
+kextstat | grep -i usb  | awk '{print $6}' | sort
+```
+
+## Display the system message buffer
+
+```
+dmesg
+```
+
+## Setup vim plugins
+
+https://github.com/tpope/vim-pathogen
+
+## Push up to a specific commit
+
+```
+git push origin SHA:branch_name
+```
+
+## Run a simple HTTP server using nc
+
+```
+nc -kl 5432 -c 'echo -e "HTTP/1.1 200 OK\r\n$(date)\r\n\r\n";echo "<p>How are you today?</p>"'
+while true ; do nc -l 80  < index.html ; done
+```
+
+## Find time a process has been running
+
+```
+for pid in `ps auwwwx | grep uwsgi | grep clearcare.yaml | awk '{print $2}'`; do
+  ps -p $pid -o etime=
+done
+```
+
+## Add/remove 200ms delay to a network interface
+
+```
+root@ccdev# tc qdisc add dev lo root netem delay 200ms
+root@ccdev# tc qdisc del dev lo root
+```
+
+## Correct perms for ssh files/dirs
+
+```
+chmod 700 /home/your_user/.ssh
+chmod 600 /home/your_user/.ssh/authorized_keys
+```
+
+## Get IP address for a given network device
+
+```
+ifconfig eth1 | grep "inet addr" | awk '{ print substr($2,6) }
+```
+
+## ssh-agent on the mac
+
+```
+sudo launchctl load -w /System/Library/LaunchAgents/org.openbsd.ssh-agent.plist
+sudo launchctl unload /Path
+```
+
+
+## To start a differently named key at login:
+
+```
+ssh-add -K ~/.ssh/some_key
+```
+
+## Strip multiple characters with sed
+
+```
+sed 's/[<>,]//g'
+```
+
+## Default a command line arg in bash
+
+```
+FOO=${VARIABLE:-default}
+```
+
+## Patching in Git
+
+```
+git apply --check tests.patch
+git apply -v --check tests.patch to see where it's blaring
+```
+
+## Getting LOC changed in a commit range
+
+```
+git log --author=Brian --since="Feb 15, 2014" --no-merges --numstat --pretty="%H" -- tests | awk 'NF==3 {plus+=$1; minus+=$2} END {printf("+%d, -%d\n", plus, minus)}'
+```
+
+## OS X
+
+```
+sudo killall -HUP mDNSResponder
+```
+
+## Ubuntu
+
+Uninstall and purge a debian pakages…removes conf files: dpkg -P elasticsearch
+Install a package from a file: dpkg -i elasticsearch-0.90.7.deb
+
+## Reset guest additions version
+
+```
+VBoxManage guestproperty set ae63d283-bd8d-44ea-be05-e61c9b2a8f73  /VirtualBox/GuestAdd/Version
+```
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