In case a faulty script started by .bashrc or .profile is failing and crashing SSH initiation, you could still login and fix the issue by running shell directly via ssh.
The command is –
ssh -t {username}@{hostname} /bin/shMigrate data from one Cassandra server to another using medusa
Here are the steps I followed to get my dev instance of cassandra copied to a new server (both single node instances)
I’ve used medusa tool for the same. You can read more about it here
Installation
Install medusa on both source and destination cassandra-servers, by running the following commands on both –
curl -1sLf 'https://dl.cloudsmith.io/public/thelastpickle/medusa/setup.deb.sh' | sudo -E bash sudo apt update sudo apt-get install cassandra-medusa
Export Data from Source DB
#ssh into source server and do these
mkdir ~/cassandra-bkup
sudo cp /etc/medusa/medusa-example.ini /etc/medusa/medusa.ini
sudo vi /etc/medusa/medusa.ini
# Search for, and set these values in the ini file
storage_provider = local
base_path = /home/{username}/cassandra-bkup
# Save and Exit
medusa backup --backup-name=dev-db-data --mode=full
#compress output folder
tar -czf dev-db-bkup-tar ~/cassandra-bkup
# SCP the backup directory to destination server
scp -r -i <key-file> dev-deb-bkup-tar {dest-user}@{dest-server}:~/
Import data in Target DB
# ssh into target serer and do these
tar -xzf dev-deb-bkup-tar
ls ls /home/{username}/cassandra-bkup/cassandra_backups/
#note down the folder name parallel to the folder index, let it be {sourceHostLocalName}
sudo /etc/hosts
#add an entry with local nodes IP and host name as {sourceHostLocalName}.
#You can remove this later
# save /etc/hosts and Exit Vim.
sudo medusa restore-node --keyspace={keyspace of intereset} --backup-name=dev-db-dataVerify Imported data
cqlsh {targetNodeIp}
desc keyspaces #verify you have the source keyspace created
use {keyspaceOfInterest}
desc tables; #verify all your tables in the source are recreated here.That’s it. You should now be able to work with your new Cassandra node!
A JS assistant to remind us to exercise during WFH days
Here is a weekend hack I wrote to remind me to get up from my workstation and do some lightweight exercises during the WFH days – Fit@WFH
Some of the features are –
- Purely in browser side JS (your data stays at your computer)
- Reminds you to workout during the tail end of every hour
- Reminder both in Voice and Browser Notification
- You can select the exercises you are comfortable with from a list
- Built for desktop (i.e, for serious WFH’ers )
I guess someone else might also find tremendous value from it. So if you too are caught in a sedentary lifestyle and want to move more, go ahead – book mark and use it !
Launch WFH Fitness Utility
Flush DNS cache in Ubuntu 20.xx and above
On bash, run –
sudo systemd-resolve --flush-caches
Should be done.
Change the datacenter set in cassandra-rackdc on Ubuntu
Problem: Changing just the datacenter name in cassandra-rackdc.properties gives the error:
Cannot start node if snitch's data center [newName] differs from previous data center [oldName]. Please fix the snitch configuration, decommission and rebootstrap this node or use the flag -Dcassandra.ignore_dc=true.Solution:
If you are just beginning to setup you cassandra cluster, and is ok to reset the data to bootstrapped state, do this
sudo service cassandra stop sudo rm -R /var/lib/cassandra sudo mkdir /var/lib/cassandra sudo chown cassandra /var/lib/cassandra sudo service cassandra start
If you need to persist the existing data, do this
sudo vi /etc/cassandra/cassandra-env.sh
# edit the JVM_OPTS line to make it look like below
JVM_OPTS=\"$JVM_OPTS -Dcassandra.ignore_rack=true -Dcassandra.ignore_dc=true\"
sudo service cassandra restart
This should normally resolve the dc name correction in rack-dc properties file.
RabbitMQ installation fails in in the last leg of setting up in ubuntu 20.04
Error:
Setting up rabbitmq-server (3.8.16-1) … Job for rabbitmq-server.service failed because the control process exited with error code. See "systemctl status rabbitmq-server.service" and "journalctl -xe" for details. invoke-rc.d: initscript rabbitmq-server, action "start" failed.
Reason: libtinfo.so library missing.
Solution:
sudo apt install libncurses5
Note: No need to reattempt the installation.
An “eat dosa!” reminder for busy kids :)
Here is a one hour HTML app that you can use to repeat recorded audio to remind your busy kids they have to finish that food on the table, while watching their favorite videos on YouTube.
To use the app is this simple –
- Click on record button. Give permission to access microphone if it asks for it.
- The recording automatically stops in 4 seconds and replays what it recorded. You can re-record till you are satisfied with the playback.
- Now you can set the number of seconds of interval, between which the above audio has to be repeated.
- Click on “Start Reminder” button to start the reminders.
- When your kid is done eating, you can stop the reminders by clicking “Stop Reminder” button
Happy parenting !
Enable dark mode for Chrome on desktop
Dark mode is great to protect your eyes, more so if you are a coder.
Here is how you can apply dark more on chrome on your desktop –
- In the address bar paste this address : chrome://flags/#enable-force-dark
- Change the setting “Force Dark Mode for Web Contents” from default to “enabled”
That’s it. Now you can have easy on eyes theme on Chrome, just like your IDE !
NPM install gives error : Cannot find module ‘semver’
Problem:
We get this error when we do npm install –
Error: Cannot find module ‘semver’
Require stack:
- /usr/share/npm/lib/utils/unsupported.js
- /usr/share/npm/bin/npm-cli.js
at Function.Module._resolveFilename (node:internal/modules/cjs/loader:924:15)
at Function.Module._load (node:internal/modules/cjs/loader:769:27)
at Module.require (node:internal/modules/cjs/loader:996:19)
at require (node:internal/modules/cjs/helpers:92:18)
at Object. (/usr/share/npm/lib/utils/unsupported.js:2:14)
Reason:
Version issues
Fix:
Run these commands
sudo rm -rf /usr/local/bin/npm /usr/local/share/man/man1/node* ~/.npm sudo rm -rf /usr/local/lib/node* sudo rm -rf /usr/local/bin/node* sudo rm -rf /usr/local/include/node* sudo apt-get purge nodejs npm sudo apt autoremove sudo apt-get install nodejs npm
Try now. Should be fixed !
Fix : Docker node down after restart
Problem: One of the docker nodes does not start up after restart. Error in the log is
Reason: Docker swarm and network stack sucks.
Fix: