clive@debian:~$ sudo fdisk -l /dev/sda
Disk /dev/sda: 38.3 GiB, 41110142976 bytes, 80293248 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x06ff1652

Device     Boot    Start      End  Sectors  Size Id Type
/dev/sda1  *        2048 76077055 76075008 36.3G 83 Linux
/dev/sda2       76079102 78155775  2076674 1014M  5 Extended
/dev/sda5       76079104 78155775  2076672 1014M 82 Linux swap / Solaris

clive@debian:~$ sudo update-initramfs -u -k all[/cdoe]
/boot/initrd.img-all[/cdoe] does not exist. Cannot update.

clive@debian:~$ sudo swapon --show
NAME      TYPE       SIZE USED PRIO
/dev/sda5 partition 1014M   0B   -1

clive@debian:~$ sudo swapon /dev/sda5
swapon: /dev/sda5: swapon failed: Device or resource busy


clive@debian:~$ sudo blkid
/dev/sda1: UUID="e166e767-42b5-4c35-9978-db5e042e0b08" TYPE="ext4" PARTUUID="06ff1652-01"
/dev/sda5: UUID="71cf9f99-7de4-418a-805e-67d5ed7435fd" TYPE="swap" PARTUUID="06ff1652-05"

clive@debian:~$ sudo nano /etc/initramfs-tools/conf.d/resume

Result from above is:-  RESUME=UUID=71cf9f99-7de4-418a-805e-67d5ed7435fd

clive@debian:~$ sudo swapon /dev/sda5
swapon: /dev/sda5: swapon failed: Device or resource busy