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creating swapfile on Centos 5.9 linux

Hi,

I need more memory so I was reading this page:
https://www.linux.com/news/software/applications/8208-all-about-linux-swap-space

#free -m
             total       used       free     shared    buffers     cached
Mem:          1024       1024          0          0          0          0
-/+ buffers/cache:       1024          0
Swap:            0          0          0

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A couple of questions:
(1)
I ran this:

dd if=/dev/zero of=/swapfile bs=1024 count=2048576

the above command ran fine.

But this command gives me a "command not found" error:
mkswap /swapfile

Also, I don't have the command:
swapon -s

(2)
If I create the swapfile then will it free my physical RAM?

(3)
Are there any other considerations I need to make so nothing breaks or happens?

Thank you and Father bless<><

SOLUTION

Seth Simmons

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gheist

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TobiasHolm

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ssvl

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Victor Kimura

ASKER

Ok, thank you all! =)

So I shouldn't use swap at all then? I was going to just test and see what the performance will be like. How do I undo the swapfile after the test? What are the commands to unswap the file or partition?

@gheist, just curious how do I find out how which device is the swap partition? I'm on a VDS from gd hosting. Currently, Centos 5.9.

SOLUTION

Seth Simmons

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Victor Kimura

ASKER

I get this with fdisk:

root@ip-184-168-116-73 [/home/myultrat/public_html/l4]# fdisk -l
bash: fdisk: command not found
root@ip-184-168-116-73 [/home/myultrat/public_html/l4]# /sbin/fdisk -l
cannot open /proc/partitions

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SOLUTION

Seth Simmons

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Victor Kimura

ASKER

yeah, it's a VDS with godaddy. Anyone suggest a better VDS that doesn't have restrictions? A friend recommended mochhosting.

ASKER CERTIFIED SOLUTION

gheist

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Victor Kimura

ASKER

@gheist, wow, those are really cheap. Are there some good tutorials on compcache setup? Tried looking but there doesn't seem to be that much info on it. I'm running Centos 5.9 but RHEL is similar I would think.

Victor Kimura

ASKER

Bless you all! =)

gheist

On RHEL6 you can use compcache as an indication when swapping occurs.
RHEL 5, CentOS 5 , Oracle Linux 5 , Scientific Linux Boron do not fall in RedHat v6 category by any means.

Victor Kimura

ASKER

@gheist, ok, thanks! Are there tutorials on compcache? How does one view it and if there is something we need it make it active or does it come standard?

gheist

This is good:
https://extremeshok.com/1448/1448/