Linux Commands

• yum repo checks

yum whatprovides openssl

• Openssl commands

# Generate private key
openssl genrsa -out opscode.key 2048
# Use the private key and generate Certificate Signing Request
openssl req -new -key opscode.key -out opscode.csr -subj "/CN=opscode/O=opscode"
openssl x509 -in 

SSH agent forwarding

• Login to private instance thr bastion without copying the pem to bastion

ssh-add -k ~/.ssh/myssh.pem
ssh -A -i ~/.ssh/myssh.pem ec2-user@bastion_host
ssh private_ip

overwrite the files

dd if=/dev/zero of=/home/ec2-user/test.txt bs=1M count=10

• stress

while :
do
    stress --cpu 2 -m 1 -d 1 --timeout 30 2>&1 > /dev/null
    sleep 5
done

while :
do
    echo "Calculating pi's 3000 digits..."
    sudo cgexec -g cpu:/formulaone bash -c 'time echo "scale=3000; 4*a(1)" | bc -l | head -n1'
done

echo "Killing instance B (port 8002)"
ps auxf | grep python | grep 8002 | awk '{system("sudo kill " $2)}'
sleep 0.5
systemctl status faas001_b --no-pager

find

• find the files bigger than 100 Mb and list

find / -xdev -size +100M -exec ls -lh {} \;

• Find the log file bigger than 50 Mb and older than 180 days then remove

find /var/log -name "*.log.*" -type f -size +50M   -mtime +180 -exec rm -rf {} \;

date

date '+%Y%m%dT%H%M%S'