Dev {Tricks}

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How to Add Swap Space/file on CentOS 7 and CentOS 8

Before You Begin

check if your CentOS installation already has swap enabled by typing:

swapon –show

Empty output means that your system does not have swap enabled. Otherwise, swap enabled. Note that you may have multiple swap partitions and/or files.

Creating a Swap Partition

Creating a Swap File

 

First, create a file which will be used as swap space 1GB:

fallocate -l 1G /swapfile

If the fallocate utility is not available

sudo dd if=/dev/zero of=/swapfile bs=1024 count=1048576

Ensure that only the root user can read and write the swap file

chmod 600 /swapfile

Next, set up a Linux swap area on the file:

mkswap /swapfile

Run the following command to activate the swap:

swapon /swapfile

Make the change permanent by opening the /etc/fstab file:

vi /etc/fstab

and pasting the following line:

/swapfile swap swap defaults 0 0

Verify that the swap is active

swapon –show

or

free -h

Adjusting the Swappiness Value

Swappiness can have a value between 0 and 100. A low value will make the kernel to try to avoid swapping

cat /proc/sys/vm/swappiness

To set the swappiness value to 10

sysctl vm.swappiness=10

To make this parameter persistent across reboots append the following line to the /etc/sysctl.conf file:

vm.swappiness=10

Removing a Swap File #

Start by deactivating the swap space by typing:

sudo swapoff -v /swapfile

Next, remove the swap file entry /swapfile swap swap defaults 0 0 from the /etc/fstab file.

Finally, delete the actual swapfile file with rm :

sudo rm /swapfile

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How to Create Swap Partition in CentOS 7 & CentOS 8

Swap Partition Size

RedHat

RedHat distributions should have a swap partition size of 20% of the available RAM. The minimum amount of RAM is 4GB.
CentOS

CentOS provides the following guidelines:

The swap partition should be twice the amount of RAM if the total RAM amount is below 2GB.
If you have more than 2GB of RAM, then the swap partition should be the size of RAM + 2 GB. For example, use 8GB of swap for 6GB of RAM.

Ubuntu/Debian

Ubuntu has based its swap size recommendations on the use of hibernation.

If you use hibernation, the swap partition should be the same as the amount of RAM plus the square root of the RAM amount.

If you don’t use hibernation:

For less than 1GB of RAM, the swap partition size should be at least the same as the amount of RAM and, at most, double the amount of RAM.
For more than 1GB of RAM, create a swap partition at least equal to the square root of the RAM amount and, at most, double the RAM amount.

 

swapon Command

swapon –show

Check /proc/swaps File

cat /proc/swaps

Comman to check your swap

free -h

How to Create a Swap Partition

1. Run the fdisk command for the disk you want to partition:

sudo fdisk [disk_path]

Replace [disk_path] with your disk identifier.

2. Type p and press Enter for an overview of the disk.

The output provides information about the available disk space for a new partition. If the last partition ends before the last sector of the hard drive, there is enough space to create a new partition. The output above shows the entire disk space is available for creating a new partition.

3. Type n and press Enter to create a new partition. For partition type, enter p and press Enter.

4. Set the partition number (or keep the default number 1) and press Enter to confirm.

5. Enter the first available sector for the new partition and press Enter. You can also keep the default one offered.

6. Set the last available sector for the partition. You can specify the partition size in KiB, MiB, or GiB units. We will create a swap partition of 1GiB, so the command is:

+1G

7. Press p to verify the partition creation and confirm with Enter.

8. By default, the partition type is 83, while 82 is a partition type identifier for swap space.

Type t and press Enter to change the partition type. Change the value to 82 and press Enter.

9. Verify the change with p and confirm with Enter.

10. fdisk doesn’t make any changes to the disk before confirmation. To proceed with the changes, type w, and press Enter.

12. Update the partition table using the following syntax:

sudo partprobe [disk_path]

13. Use the mkswap command to format the partition for swap space. The command writes a swap signature in the partition, leaving the rest unformatted. The unformatted space stores the memory pages.

Use the following syntax to format the partition and create a swap space:

sudo mkswap [disk_path]

After formatting, the swap partition is created and ready to use.

How to Initialize/Enable a Swap Partition

3. Make Swap Persistent (Optional)

Include the partition in the /etc/fstab file to ensure the swap partition activates on boot.

vi /etc/fstab

Add the following line at the end:

/dev/sdb none swap sw 0 0

Replace /dev/sdb with the path to your swap partition.

How to Change the Size of a Swap Partition

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Merging OJS

Limitations :

  1. Article ID changed.
  2. Some components that are not merged and the transfer process must be done manually.
  3. Journals can be offline for some time to ensure that there is a similarity of data between previous journals and destination journals.
  4. Change of destination url of DOI (need to do manual change request activity to DOI provider like Crossref).

Considerations:

  1. Redirection of DOI links to new url.
  2. OJS upgrade of journals to make similarity.
  3. Backup

Targets:

  1. Moving static contents.
  2. Transferring article data with publishing status.
  3. Transferring user data.

Shortcomings:

  1. In the articles, we have to assign user manually.
  2. If there is a review, submission, or copyediting process that you want to move, you have to do the process manually one by one manually, at this time we have not found the right method to automate this process.
  3. Usage Statistics of each published article will be 0.
  4. The date in the statistics will be reset to the date when you import data into the journal.

Workflow:

  1. OJS upgrade to match version of all journals.
  2. Create journal and copy static content manually.
  3. Transfer articles, issues, users
  4. Update articles

 

 

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How To Move Home Directory To New Partition Or Disk In Linux

Get Partition Information

To get the block device information using the lsblk command, run:

lsblk

As stated earlier, we can also use the fdisk command to get the block device information.

sudo fdisk -l

To check under which partition the home directory is mounted, use the df command. In my case, it is mounted under /.

df -h /home

Create New Partition

Let’s create a new partition from the new drive where the home partition will be mounted. I will be using the fdisk utility to create a partition. In my case, I will add partition on /dev/sda disk.

sudo fdisk /dev/sda

Type “n” to create a new partition.

It will prompt you to choose the partition type, partition number, first sector, and last sector.

Type “w” and it will write the changes to the partition table.

Now verify if the new partition (i.e. sdb1 -> 10G) is created by listing the block device information with the lsblk command:

lsblk /dev/sda

Format and mount the Partition

sudo mkfs.ext4 /dev/sdb1

Now the partition can be mounted to any directory as you wish. Since we are going to mount this directory temporarily, I am choosing /mnt directory.

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Linkedin Post Share Solution

Resetting LinkedIn Link Previews for Accurate Content Display

To clear LinkedIn’s link preview cache, follow these steps:

Step 1: Visit the LinkedIn Post Inspector tool at www.linkedin.com/post-inspector/.

Step 2: Enter the URL you want to share.

Step 3: Click ‘Inspect’. You’ll see the updated preview image and content.

Step 4: Now, try sharing your URL on LinkedIn. This should display the new preview content and image.