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cloud engineer

time

Set Linux Time Zone

Here’s another way of setting Linux time zone.

Check server time.

# check server time
date

Change to local time.

# set to local time
rm /etc/localtime
ln -s /usr/share/zoneinfo/America/Los_Angeles /etc/localtime

Check server time again.

# check server time again
date

IAM List Access Keys

Here’s how to list all the access keys in AWS via Python.

import logging
import boto3
from botocore.exceptions import ClientError
 
# set aws profile
session = boto3.Session(profile_name="default")
 
# get list of users
 
iam = session.client('iam')
users = iam.list_users()
 
# display results
print("{0:<20} {1:<25} {2:<15} {3:<10}".format('UserName', 'AccessKey', 'Status', 'CreateDate'))
print("----------------------------------------------------------------------------------------")
 
for a in users['Users']:
    user = a['UserName']
    # get keys
    keys = iam.list_access_keys(UserName=user)
    for b in keys['AccessKeyMetadata']:
        username = b['UserName']
        accesskeyid = b['AccessKeyId']
        status = b['Status']
        createdate = str(b['CreateDate'])
        print("{0:<20} {1:<25} {2:<15} {3:<10}".format(username, accesskeyid, status, createdate))

Elapse Time on Bash Script

Here’s a nice little Bash function in a script to display the elapse time. It’s a nice function for showing how long a process ran.

#!/bin/bash
# pass number of seconds as argument. 
# Example below calculates 1000s.
# elapse.sh 1000
function show_time () {
    num=$1
    min=0
    hour=0
    day=0
    if((num>59));then
        ((sec=num%60))
        ((num=num/60))
        if((num>59));then
            ((min=num%60))
            ((num=num/60))
            if((num>23));then
                ((hour=num%24))
                ((day=num/24))
            else
                ((hour=num))
            fi
        else
            ((min=num))
        fi
    else
        ((sec=num))
    fi
    echo "$day"d "$hour"h "$min"m "$sec"s
}
show_time $1

Chrony Service

The chrony service actually does not change the time. The misconception is that the chrony service is setting the time given by the NTP server. This is not what’s happening. The chrony service is just telling the system clock to go faster or slower. This is the reason why sometimes even though the time is wrong and the NTP server is working, the time does not get corrected immediately. It takes a little while.

Calculate Epoch Time to Date

Here’s how to calculate epoch time using the Linux date command.

# Linux
date --date @1561266781
date -d @1561266781
# MacOS
date -r 1561266781

Output is : Sun Jun 23 05:13:01 UTC 2019

Show current epoch time.

date +%s

Output: 1561642643