Dd: out of memory

Linux
,
1

I am following your tutorial:
https://www.cyberciti.biz/faq/how-to-create-a-linux-swap-file/
I want to create 8GB swap space but when I run:

dd if=/dev/zero of=/swap-file count=1 bs=8GB

I am getting an error on screen:

dd: out of memory

I do have 8GB ram and free command said:

              total        used        free      shared  buff/cache   available
Mem:           7230        5002        2058           0         169        2011
Swap:             0           0           0

How can I tell dd to create 8GB swap file?

2

The following error indicates that dd can not allocate 8GB ram

fatal error: runtime: out of memory
dd: out of memory

Your free command shows you only have 2011MB free memory. Linux and Unix like oses do aggressive caching[1]. You can flush disk caching using the following command:

echo 3 | sudo tee /proc/sys/vm/drop_caches

Verify it:

free -m

Fixing dd: out of memory

But, this will not solve your problem as you have 8GB max ram. To fix this simply lower dd bs=NN value. For instance try using 1GB x 8 count as follows:

sudo dd if=/dev/zero of=/swap-file count=8 bs=1GB

Where,

  • if=/dev/zero : Read from /dev/zero
  • of=/swap-file : Write to /swap-file
  • count=8 : Copy only N input blocks
  • bs=1GB : Read and write 1GB bytes at a time

In short, you must specify bs count less than available memory and multiply with count to get the desired result.
[1] https://www.linuxatemyram.com/

1 Like
3

That did it. I am so stupid and should have thought about max ram. That is the difference between trained Linux sysadmin and developer. Thank you once again.