Skip to main content

Linux

· 3 min read

Open in Notion

How to add swap on CentOS​

Check the System for Swap Information​

swapon -s
free -m

total       used       free     shared    buffers     cached
Mem:          3953        315       3637          8         11        107
-/+ buffers/cache:        196       3756
Swap:            0          0       4095

Check Available Storage Space​

df -h

Filesystem      Size  Used Avail Use% Mounted on
/dev/vda1        59G  1.5G   55G   3% /
devtmpfs        2.0G     0  2.0G   0% /dev
tmpfs           2.0G     0  2.0G   0% /dev/shm
tmpfs           2.0G  8.3M  2.0G   1% /run
tmpfs           2.0G     0  2.0G   0% /sys/fs/cgroup

Create a Swap File​

sudo dd if=/dev/zero of=/swapfile count=10240 bs=1MiB
ls -lh /swapfile

-rw-r--r-- 1 root root 4.0G Oct 30 11:00 /swapfile

Enable a Swap File​

sudo chmod 600 /swapfile

ls -lh /swapfile
-rw------- 1 root root 4.0G Oct 30 11:00 /swapfile

sudo mkswap /swapfile
Setting up swapspace version 1, size = 4194300 KiB
no label, UUID=b99230bb-21af-47bc-8c37-de41129c39bf

sudo swapon /swapfile
swapon -s
Filename                Type        Size    Used    Priority
/swapfile               file        4194300 0     -1

free -m
total       used       free     shared    buffers     cached
Mem:          3953        315       3637          8         11        107
-/+ buffers/cache:        196       3756
Swap:         4095          0       4095

Make the Swap File Permanent​

Edit the file with sudo privileges in your text editor:

sudo nano /etc/fstab

At the bottom of the file, you need to add a line that will tell the operating system to automatically use the swap file that you created:

/swapfile   swap    swap    sw  0   0

User and sudo​

How To create a new sudo user on CentOS​

First create a new CentOS user account from the command line. For example, create the marlena user account, run:

adduser marlena

Set the password for marlena user by typing the following passwd command:

passwd marlena

A new user account was created. Verify it:

id marlena

In CentOS 8 Linux server all members of the wheel group have sudo access. So all you have to do is append user account to the wheel group using the usermod command command:

usermod -aG wheel marlena

User account marlena now have sudo privileges. Verify it by running the id command or grep command on /etc/passwd and /etc/group files:

id marlena
grep '^marlena' /etc/passwd
grep '^wheel' /etc/group

How to grant or add existing user account to sudo on CentOS​

Below is to give sudo access to an existing user named vivek by adding the user to the wheel group:

usermod -aG wheel vivek
id vivek

Deleting a user account in CentOS 8​

userdel -r {userName}