[SOLVED] Swap Error: skipping - it appears to have holes

[bootsie123`]

Hi. I'm trying to create a swap file with Debian Jessie and I keep running into an error when running

swapon /swap

Here are my steps I'm using to create said swap file

Code: Select all

dd if=/dev/zero of=/var/swap bs=1M count=4096

chmod 600 /var/swap

mkswap /var/swap

swapon /var/swap

I've also tried editing

/etc/fstab

before running

swapon

and that didn't fix the issue either. Any ideas on how I can fix this?

[p.H]

Do you really need a 4-TB swap file ?
A swap file must not have holes because the kernel needs to map all its blocks to the underlying block device, but the dd command should create a file without holes.
What is the filesystem type for /var ?

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df -hT /var

[Head_on_a_Stick]

Code: Select all

fallocate -l 4G /var/swap

^ Quicker than `dd`

[p.H]

The OP's dd command creates a 4-TB swap file, not 4-GB.
swapon and mkswap man pages warn against using fallocate on some filesystems (ext4, xfs) because it can create a file with holes.

[Head_on_a_Stick]

The OP's dd command creates a 4-TB swap file, not 4-GB.

Curse my maths

swapon and mkswap man pages warn against using fallocate on some filesystems (ext4, xfs) because it can create a file with holes.

But the OP already has holes so perhaps it's worth a try?

[bootsie123`]

To clear up the confusion. I didn't realize this until you guys said something, but I meant 4GB. Not 4TB. I'm not exactly sure what I was thinking when I wrote that part. The file system I'm using is zfs. I ran fallocate as Head_on_a_Stick suggested and I get

fallocate: fallocate failed: Operation not supported

[Head_on_a_Stick]

https://github.com/zfsonlinux/pkg-zfs/w ... wap-device

[bootsie123`]

There we go. That worked. Thanks!

[None1975]

The OP's dd command creates a 4-TB swap file, not 4-GB.

I'm curious how much he has RAM ...

[bootsie123`]

The OP's dd command creates a 4-TB swap file, not 4-GB.

I'm curious how much he has RAM ...

I made a mistake. It was supposed to be 4GB and not 4TB. Although, I wish I had 4TB of ram. Anyways, hope that clears things up.

[p.H]

Looks like zfs is another filesystem which does not support Linux swap files, like btrfs and nilfs2.
Linux swap files are broken by design. Do not use them.

Tip : if you really need to create a temporay swap file on an unsupporting filesystem, you can create a loop device with losetup.