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@tvvignesh tvvignesh/ops.md
Last active May 18, 2019

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Quick Commands

SEMODULE DISABLE IN CentOS

sudo cat /var/log/audit/audit.log | grep nginx | grep denied | audit2allow -M mynginx

sudo semodule -i mynginx.pp

ALLOW HTTP & HTTPS TRAFFIC IN FIREWALL

sudo systemctl stop firewalld

sudo systemctl disable firewalld

(or)

firewall-cmd --permanent --zone=public --add-service=http

firewall-cmd --permanent --zone=public --add-service=https

firewall-cmd --reload

Add intermediate SSL Certificate to Domain Certificate

cat your_domain_name.crt DigiCertCA.crt >> bundle.crt

PPK TO PEM

sudo apt-get install putty-tools

puttygen server.ppk -O private-openssh -o server.pem

Reload Nginx without Restart

nginx -s reload

SSH AWS

ssh -i /path/my-key-pair.pem ec2-user@IP

KEEP SSH ALIVE

sudo nano /etc/ssh/ssh_config

Host *

ServerAliveInterval 30

Creating a Service in CentOS

sudo nano /etc/systemd/system/xyz.service [Unit]

Description=xyz Service After=network.target

[Service]

Type=simple User=username ExecStart=/usr/bin/xyz -s Restart=on-abort

[Install]

WantedBy=multi-user.target

sudo systemctl daemon-reload

sudo systemctl start xyz

Installing Docker

sudo yum install -y yum-utils device-mapper-persistent-data lvm2

sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

sudo yum install docker-ce

sudo systemctl start docker

sudo systemctl enable docker

Docker compose for root

sudo ln -s /usr/local/bin/docker-compose /usr/bin/docker-compose

Increase Compose Timeout

COMPOSE_HTTP_TIMEOUT=200 docker-compose up

Docker registry deployment

sudo docker run -d \ -p 5000:5000 \ --restart=always \ --privileged \ --name registry \ -v /opt/registry:/var/lib/registry \ registry:2

Reference: https://www.digitalocean.com/community/tutorials/how-to-set-up-a-private-docker-registry-on-ubuntu-14-04#step-4-%E2%80%94-setting-up-authentication

Fix local docker registry error when logging in from ubuntu

sudo mv /usr/bin/docker-credential-secretservice /usr/bin/docker-credential-secretservice_x

See disk usage by Docker

docker system df

Remove all dangling volumes

docker volume rm `docker volume ls -q -f dangling=true`

Generating password file

sudo yum install httpd-tools sudo htpasswd -c /etc/nginx/htpasswd.users username

ELASTICSEARCH

Set vm.max_map_count:

echo 'vm.max_map_count=262144' >> /etc/sysctl.conf

sysctl -p

Set ulimit and noproc for systemd processes:

https://unix.stackexchange.com/questions/345595/how-to-set-ulimits-on-service-with-systemd

Unassigned shards:

https://www.datadoghq.com/blog/elasticsearch-unassigned-shards/

GIT

Remove from GIT Tracking

git rm --cached file.xyz

Compress loose objects

git gc --aggressive

SFTP CONFIG

Follow the instructions in https://www.howtoforge.com/tutorial/how-to-setup-an-sftp-server-on-centos/

sudo nano /etc/ssh/sshd_config

Replace the line PasswordAuthentication no with PasswordAuthentication yes. (Uncomment this line if commented.) Save and close this file.

sudo service sshd reload

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