linux

Mac vs Linux Date

August 17, 2023

Converting Mac and Linux Dates

Linux

#!/bin/bash
start_time=$(date +%s)
log=$(date -d @$start_time +%Y%m%d-%H%M%S) 
start=$(date -d @$start_time)
echo $start_time
echo $log
echo $start
sleep 10
stop_time=$(date +%s)
stop=$(date -d @$stop_time)
echo $stop_time
echo $stop

Mac

#!/bin/bash
start_time=$(date +%s)
log=$(date -r $start_time +%Y%m%d-%H%M%S) 
start=$(date -r $start_time)
echo $start_time
echo $log
echo $start
sleep 10
stop_time=$(date +%s)
stop=$(date -r $stop_time)
echo $stop_time
echo $stop

Same output for both

1692292771
20230817-171931
Thu Aug 17 05:19:31 PM UTC 2023
1692292781
Thu Aug 17 05:19:41 PM UTC 2023

Date From A Year Ago

June 18, 2023

Here’s a handy little script that has multiple applications to calculate date from a year ago.

#!/bin/bash
now=$(date +%Y%m%d-%H%M%S)
# mac os
year_old=$(date -v-1y +%Y%m%d-%H%M%S) 
# linux os 
year_old=$(date -d "-1 year" +%Y%m%d-%H%M%S)
echo $now
echo $year_old

Mac Os and Linux has slightly different formats. Pick one based on your OS.

Results

20230618-084940
20220618-084940

Change Hostname Amazon Linux

June 6, 2023

Here’s how to make a hostname stick on Amazon Linux.

Set preserve_hostname to true in /etc/cloud/cloud.cfg.

preserve_hostname: true

Set the hostname in /etc/sysconfig/network.

HOSTNAME=server.domain.com
NETWORKING=yes
NOZEROCONF=yes

Reboot the server to make sure hostname sticks after a reboot.

shutdown -r now