Re: Adding file swap on btrfs

[Jonathan Billings <billings@xxxxxxxxxx>]

On Dec 19, 2022, at 15:10, Samuel Sieb <samuel@xxxxxxxx> wrote:

On 12/19/22 11:58, Neal Becker wrote:

I've just installed f37 on a new lenovo x1 carbon.

One thing, the installation didn't setup any swap (other than zswap).

After a bit of reading I found

sudo btrfs filesystem mkswapfile -s 32G /swapfile

But:

 sudo swapon -v /swapfile

swapon: /swapfile: found signature [pagesize=4096, signature=swap]

swapon: /swapfile: pagesize=4096, swapsize=1073741824, devsize=34359738368

Although I created 32G swapfile, only 1G is used.

swapon

NAME       TYPE       SIZE USED PRIO

/dev/zram0 partition    8G 6.3M  100

/swapfile  file      1024M   0B   -2

What's wrong?

Something is wrong with how it creates the swap format.  Just run "mkswap /swapfile" and it will be  

I totally missed the size discrepancy. 

I believe in new btrfs versions, you can use:

# btrfs filesystem mkswapfile swapfile
# swapon swapfile

https://btrfs.readthedocs.io/en/latest/Swapfile.html

Otherwise you need to set the No_COW attribute with `chattr +C /path/to/swap/directory`. 

--

Jonathan Billings

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