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enable

CloudWatch Notifications

How to give someone access to enable/disable CloudWatch notifications.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "cloudwatch:DescribeAlarms",
                "cloudwatch:EnableAlarmActions",
                "cloudwatch:DisableAlarmActions"
            ],
            "Effect": "Allow",
            "Resource": "*"
        }
    ]
}

Enable Core Dumps

Core dumps are triggered by kernel when a program crashses. It saves memory to a file.

How to enable core dumps.

ulimit -S -c unlimited

Enable core dumps permanently. Edit /etc/security/limits.conf. Add the following.

* soft core unlimited

Disable core dumps.

ulimit -S -c 0

Disable core dumps permanently. Edit /etc/security/limits.conf. Add the following.

* soft core 0
* hard core 0

AWS CloudWatch Alarms

How to enable and disable CloudWatch alarms

$ aws cloudwatch disable-alarm-actions --alarm-names myalarm --region us-east-1
$ aws cloudwatch enable-alarm-actions --alarm-names myalarm --region us-east-1

Install Syslog

How to install syslog-np on Centos 7.

cd /tmp
wget https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
yum -y reinstall ./epel-release-latest-7.noarch.rpm
chattr +i /etc/yum.repos.d/epel*
yum -y install syslog-ng

Enable syslog-np. Disable rsyslog.

systemctl enable syslog-ng
systemctl start syslog-ng
yum -y erase rsyslog

HTTPD on Redhat & Centos

Here are the commands to start, stop, enable and get the status of Apache on RHEL and CentOS.

systemctl enable httpd  # enable on bootup
systemctl status httpd  # get status
systemctl start httpd   # start
systemctl stop httpd    # stop
systemctl restart httpd # restart

AWS Enable Enhance Network Support

When changing machine types, you may be asked to enable the latest ENA driver for Enhanced Network Support on an Amazon EC2 instance. There are several instructions depending on the Linux OS flavor. Here are the instructions to enable. In some cases, you may need to rebuild the kernel module. To verify that the ena module is installed, use the modinfo command as shown in the following example.

modinfo ena

You also may have to enable the enhanced networking attribute on the instance.

aws ec2 modify-instance-attribute --instance-id instance_id --ena-support