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Set Timezone Permanently

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It’s recommended to set the clock to UTC. In rare occasions, local time may be needed.

Here’s how to set your server’s timezone permanently.

Check the date first.

date

Backup localtime. Set it to US Eastern Time.

mv /etc/localtime /etc/localtime.backup
ln -s /usr/share/zoneinfo/America/New_York /etc/localtime

Backup clock. Set it to US Eastern Time.

cp -p /etc/sysconfig/clock /etc/sysconfig/clock.backup 
> /etc/sysconfig/clock
echo ZONE=\"America/New_York\" > /etc/sysconfig/clock

Run the date again to validate.

date

EFS Tags Auto Assign Backup Tags

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Here’s a script that scans all EFS systems in several AWS accounts and regions and randomly assigns backup tags to EFS systems that are missing backup tags. This is assuming EFS is using AWS Backup service using tags to apply backup policies. If there are no backup tags, an EFS gets assigned a randomly picked backup policy.

#!/bin/bash
# log file
output="test.log"
tmpfil="temp.txt"
# empty file
> $output
# set random array
arr[0]="efs-0000"
arr[1]="efs-0400"
arr[2]="efs-0800"
arr[3]="efs-1200"
arr[4]="efs-1600"
arr[5]="efs-2000"
rand=$[ $RANDOM %6 ]
backup=${arr[$rand]}
# set accounts and regions
declare -a account=("default" "one" "two" "three" "four" "five")
declare -a region=("us-east-1" "us-east-2" "us-west-1" "us-west-2")
for i in "${account[@]}"; do
  echo "===================" >> $output
  echo $i >> $output
  echo "===================" >> $output
  for j in "${region[@]}"; do
    echo $j >> $output
        aws efs describe-file-systems \
        --query "FileSystems[*].[FileSystemId,Tags[?Key=='aws-backup']|[0].Value]" \
        --profile $i \
        --region $j \
        --output text > $tmpfil
        while read -r id tag; do
      if [[ $tag == "" ]]; then
        aws efs tag-resource \
        --resource-id $id \
        --tags Key="aws-backup",Value=${arr[$rand]} \
        --profile $i \
        --region $j >> $output
        echo "Added backup tag $backup to $id" >> $output
      elif [[ $tag == "no-backup" ]]; then
        echo "Backup tag is already set to no-backup on $id." >> $output
      else
        echo "No backup tag changes applied to $id." >> $output
      fi
    done < $tmpfil
  done
done
rm $tmpfil

GCP Set Scopes

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Here’s how to set the instance scope in GCP.

Stop the server.

gcloud compute instances stop server-name

Default scopes.

gcloud beta compute instances set-scopes server-name \
--service-account=your-service-account@gserviceaccount.com \
--scopes=default \
--project your-project-id \
--zone=us-central1-a

Change scopes by adding storage-rw to default.

gcloud alpha compute instances set-scopes servername \
--service-account=your-service-account@gserviceaccount.com \
--scopes=default,storage-rw \
--project your-project-id \
--zone=us-central1-c

Start the server.

gcloud compute instances start server-name

GCP Scope Documentation.

Change Default Editor

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Ubuntu and Linux Mint use nano as their default editor. You’ll see it if you try to edit crontab or visudo. Now, there’s nothing wrong with nano, but I prefer using vim instead. Here’s how to change the default editor.

sudo update-alternatives --config editor

You’ll be prompted to change the default editor.

There are 4 choices for the alternative editor (providing /usr/bin/editor).
 
  Selection    Path                Priority   Status
------------------------------------------------------------
  0            /bin/nano            40        auto mode
  1            /bin/ed             -100       manual mode
  2            /bin/nano            40        manual mode
* 3            /usr/bin/vim.basic   30        manual mode
  4            /usr/bin/vim.tiny    15        manual mode
 
Press <enter> to keep the current choice[*], or type selection number:

Type 3 to choose vim basic.

Timedatectl

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Here’s another way of setting your server’s timezone. See all the options under North America.

timedatectl list-timezones | grep -i America

Set timezone.

timedatectl set-timezone America/New_York

To check.

date

Restart cron if needed.

systemctl restart cron.service

Set Linux Time Zone

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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

Set User Umask

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How to set up umask for a Linux user.

# sets umask for all users
vi /etc/profile
# sets umask for a user
vi ~/.bashrc

Add the following umask line to the file.

umask 0022

Vi Display Line Numbers

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If you work with the vi or vim editors in Linux, sometimes it’s nice to be able to see the line numbers display on the editor.

Turn it on.

vim filename
:set number

Turn it off.

vim filename
:set nonumber