linux comm.txt

ipconfig - ifconfig

nmcli d - to check network

nmtui - network settings

systemctl restart network

useradd "name" "directory path"

-h help

-C copy

-M 

-s bin/nologin - login without password

chown "user" "dir path" - 

chgrp "group name" "dir path" -

chmod r g+rwx "file path" -

su "username" - switch user

vi for vi editor; ESC "i" for insert;
	ESC ":wq" for write and quit, use "!" to say important
find / -name filename

rm {file-name} - remove file

ssh root@ipaddress - to connect to another vm

hostnamectl set-hostname younameit - changing host name.

exec bash - to see that change

sestatus- selinux status

sudo tail -100 /var/log/ - to check logs.

sudo systemctl stop firewalld - stop the firewall.

useradd username	default method for adding user

useradd -m username	user with home directory

passwd username		adding password to user

useradd username -p password	single line creation

groupadd groupname	default method for adding group

groupmod 

groupdel groupname	deleting group

gpasswd groupname	it will prompt for passwd

usermod -aG groupname username		adding user to group

userdel username	deleting a user

grep groupname /etc/group		to know users in that group

man useradd/groupadd/usermod/members	more about them.

export PATH=/yourpath/bin:$PATH

printenv 	for checking environmental varaiables.

ps -ef | grep mongod		to check running processes.

sudo kill -9 PID		to kill that process.

sudo tail -f /var/log/mongodb/mongod.log - check logs

pwd to print the current path

-vvv for clear verbose

tree	for flow chart of folders.

yum whatprovides pathofelement	to find which package will provide that service.

yum provides pathofelement	to find which package will provide that service.

semanage port -a -t mongod_port_t -p tcp 27017	to open 27017 tcp port

more /proc/partitions - to check size of drives

top	-To check ram and cpu usage.

vi ~/.bashrc	-To add envi variables for that user.

sync; echo 1 > /proc/sys/vm/drop_caches	-To clear cache

echo 3 > /proc/sys/vm/drop_caches && swapoff -a && swapon -a

free -m		To check the memory cache used

Logical Volume
#to check drives and physical volumes
more /proc/partitions or fdisk -l | grep /dev
pvdisplay		(to check any physical volumes already exist)
#change with your drive names below.
pvcreate /dev/sda /dev/sdb /dev/sdc /dev/sdd
or
pvcreate /dev/sda[bcd..] if you have similar names.
#give drive name and change with your drive names
vgcreate sam-vg /dev/sda /dev/sdb /dev/sdc /dev/sdd 
#calculate total space in GB, assign to logical volume
lvcreate -L 3490G -n sam-lv(lv_name) sam-vg(vg_name)
lvcreate --extents 100%FREE --name lv_name vg_name
lvcreate -i3(stripe_number) -I64(bitesize) -L4G(space_in_gb) -n striped_logical_volume striped_vol_group
#assigns ext4 filetype to lvm
mkfs.ext4 /dev/hk6/hk6-lvdisk
#mount lv to any folder you created or already exist
mount /dev/sam-vg/sam-lv(your_volume_path) /path_of_folder_to_mount_on
#to check the disk has been created
df -h
#to unmount the lv
umount /path_of_folder_you_mounted
#remove lv created
#repair ext file system
init 1			to take system down to runlevel 1
umount /dev/sdxx	removes mount
fsck -t extx /dev/sdxx	specify ext filesystem
fsck -y /dev/sdxx	repair ext filesystem
fsck -N /dev/sda3	don't execute, just show what could be done.
mount /dev/sdxx /path	mount it back
init 3			system runlevel 3.



Cassandra on Kubes:
kubectl run givename --image=urdockerimage --port=xxxx --replicas=num --labels=key=value

kubectl get services/nodes/pods

kubectl logs pod_name

kubectl describe pods pod_name

kubectl exec -it pod_name bash


kubectl port-forward pod_name 9042:9042

kubectl get deployment

kubectl delete deployments pod_name






Docker Commands:
list all docker commands
docker	or docker container --help

See version of docker
docker version/--version/info

list all containers running
sudo docker ps 
sudo docker ps -s	with size

list docker images/containers:
docker image ls
docker container ls

list volumes and size
docker system df -v

To run a new instance
docker run --name instance_name -d cassandra:2.2.12 -p 7000:7000 -p 7001:7001 -p 7199:7199 -p 9042:9042 -p 9160:9160

To run docker through an interactive shell
sudo docker run --name name-your-cassandra -it container /bin/bash

container shell access
docker exec -it your-cassandra bash

get IP of the container
docker inspect <InstanceID>

stop a container
sudo docker stop containerID/containerName

delete a container
sudo docker kill <instanceID/Name>

delete volume of a container
docker volume rm [OPTIONS] VOLUME [VOLUME...]