error message –

root@host:~# swapon /swap-file-00
swapon: /swap-file-00: skipping - it appears to have holes.

solution – you need to zero-fill the file you are using as swap

steps to remediate this –

first of all, remove the existing file with the holes.

root@host:~# rm /swap-file-00

create the new swap file using the following command:

root@host:~# dd if=/dev/zero of=/swap-file-00 bs=1M count=5120 status=progress
5322571776 bytes (5.3 GB, 5.0 GiB) copied, 6 s, 887 MB/s
5120+0 records in
5120+0 records out
5368709120 bytes (5.4 GB, 5.0 GiB) copied, 6.08009 s, 883 MB/s

check the file type being displayed now. it’s just a data file.

root@host:~# file /swap-file-00
/swap-file-00: data

change the permissions on it:

root@host:~# chmod 600 /swap-file-00

make the new file as swap file:

root@host:~# mkswap /swap-file-00
Setting up swapspace version 1, size = 5 GiB (5368705024 bytes)
no label, UUID=738f253b-aed0-46ac-bc50-b4d1fe2d1702

check the file type being displayed now. it’s a swap file.

root@host:~# file /swap-file-00
/swap-file-00: Linux/i386 swap file (new style), version 1 (4K pages), size 1310719 pages, no label, UUID=738f253b-aed0-46ac-bc50-b4d1fe2d1702

turn on the swap, as usual

root@host:~# swapon /swap-file-00

check if it is being used as a swap file

root@host:~# swapon --show
NAME TYPE SIZE USED PRIO
/swap-file-00 file 5G 0B -2