Memory Lane

• Memory Lane
• About
• iptables
• general Linux tidbits
• scripting
• network
• lxc
• docker
• sysdig
• heroku
• notifications
• databases
• git
• mac os
• misc

About

Storage of snippets that I use too frequently to google every time, but too infrequently to actually remember the damn thing.

iptables

Simple NAT masquerade

iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE 

network

Replace default gateway

ip route replace default via 1.2.3.4

Swap mac address

ifconfig eth0 hw ether $MAC

Port Scan

nc -v -n -z -wl $TARGET $IP_FROM-$IP_TO

Easy HTTP server

python -m SimpleHTTPServer 1337

linux

Increase inotify watcher limits

echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p

scripting

Bash profiling

At the top of the script:

N=`date +%s%N`; export PS4='+[$(((`date +%s%N`-$N)/1000000))ms][${BASH_SOURCE}:${LINENO}]: ${FUNCNAME[0]:+${FUNCNAME[0]}(): }';
exec 19>$HOME/logfile
BASH_XTRACEFD=19
set -x

lxc

Attach host folder

lxc config device add $CONTAINER_NAME $MOUNT_NAME disk source=/var/www/ path=/var/www

Limit container resources

lxc config set $CONTAINER_NAME limits.cpu 2
lxc config set $CONTAINER_NAME limits.memory 2024MB
lxc config get $CONTAINER_NAME limits.memory.swap 
lxc config set $CONTAINER_NAME limits.memory.swap 1024MB
lxc config set $CONTAINER_NAME limits.memory.swap.priority 0

Forward a port from lxc to host

lxc config device add $CONTAINER_NAME $DEVICE_NAME proxy listen=tcp:0.0.0.0:1337 connect=tcp:127.0.0.1:1337

Docker

Auto update docker containers that contain label

docker run -d \
--name watchtower \
-v /var/run/docker.sock:/var/run/docker.sock \
containrrr/watchtower --label-enable -i 60

Sysdig

List docs from all docker containers

sudo sysdig -pc -cspy_logs

heroku

Cancel a stuck build

heroku plugins:install heroku-builds #first time
heroku builds:cancel $BUILD_UUID -a $APP_ID

notifications

Curl telegram message

curl -X POST \
	 -H 'Content-Type: application/json' \
	 -d '{"chat_id": "$CHATID", "text": "Message Text", "disable_notification": true}' \
	 https://api.telegram.org/bot$BOT_TOKEN/sendMessage

databases

Export from PSQL db to csv files src: https://stackoverflow.com/a/20056883

CREATE OR REPLACE FUNCTION db_to_csv(path TEXT) RETURNS void AS $$
declare
   tables RECORD;
   statement TEXT;
begin
FOR tables IN 
   SELECT (table_schema || '.' || table_name) AS schema_table
   FROM information_schema.tables t INNER JOIN information_schema.schemata s 
   ON s.schema_name = t.table_schema 
   WHERE t.table_schema NOT IN ('pg_catalog', 'information_schema')
   AND t.table_type NOT IN ('VIEW')
   ORDER BY schema_table
LOOP
   statement := 'COPY ' || tables.schema_table || ' TO ''' || path || '/' || tables.schema_table || '.csv' ||''' DELIMITER '';'' CSV HEADER';
   EXECUTE statement;
END LOOP;
return;  
end;
$$ LANGUAGE plpgsql;


---

SELECT db_to_csv('/home/user/dir');
-- this will create one csv file per table, in /home/user/dir/

git

Archive untracked files

git ls-files --others --exclude-standard -z |\

xargs -0 tar rvf ~/backup-untracked.zip

find in all commits

git rev-list –all | xargs git grep -F ‘font-size: 52 px;’

F3022…9e12:HtmlTemplate/style.css: font-size: 52 px;

E9211…8244:RR.Web/Content/style/style.css: font-size: 52 px;

Mac OS

Reset stuck Microphone Indicator and/or fix any weirdness with audio on mac os

sudo kill -9 `ps ax|grep 'coreaudio[a-z]' | awk '{print $1}'

uncategorised

Substitute shell vars in a file (Templating)

envsubst < /etc/radsecproxy.conf.tmpl > /etc/radsecproxy.conf

Make DELL PowerEdge servers shut up

# enter manual fan control mode
ipmitool -I lanplus -H $IDRAC_HOST -U root -P $IDRAC_PW raw 0x30 0x30 0x01 0x00 
# make the noise go away, shhhh...
ipmitool -I lanplus -H $IDRAC_HOST -U root -P $IDRAC_PW raw 0x30 0x30 0x02 0xff 0x09

GitHub Actions, set up Maven for local runs using act

- name: Download Maven
  run: |
	curl -sL https://www-eu.apache.org/dist/maven/maven-3/3.6.3/binaries/apache-maven-3.6.3-bin.zip -o maven.zip
	apt-get update
	apt-get -y install unzip
	unzip -d /usr/share maven.zip
	rm maven.zip
	ln -s /usr/share/apache-maven-3.6.3/bin/mvn /usr/bin/mvn
	echo "M2_HOME=/usr/share/apache-maven-3.6.3" | tee -a /etc/environment

Makeshift redirect to push prometheus metrics into a Victoria Metrics ingest. (Every time this gets used beyond just testing some prometheus maintainer gets irrationally angry)

watch -n 5 "docker exec app_container curl -s localhost:8060/metrics | curl -s -u basic:auth --data-binary @- https://victoriametrics.enterprise.com/api/v1/import/prometheus?extra_label=env=makeshift_pusher"