I have a PC with 16 GB RAM which isn’t quite enough for my obelisk-project that, among others, compiles pandoc.
I decided to add a swap partition to my system. In order to avoid trouble, I am using a conventional (i.e. slooow) hard-drive for that. My SSD is where NixOS resides and by using the conventional hard-drive, I avoid the process of resizing my partition on the SSD which would require booting into NixOS from a usb device and so on.
I used the graphical interface of gparted and create a space on the unmounted conventional hard-drive: 29.80 GiB, formatted as “linux-swap” and put this into my configuration:
# /etc/nixos/hardware-configuration.nix
swapDevices = [
{ device = "/dev/sdb2";
size = 31990;
}
];
The size I put originally is 29.80 GiB in Megabytes = 31997.
That worked immediately, without reboot. I could compile w/o running out of memory and everything seemed fine.
However …
Whenever I reboot now, I get errors which first delay the boot process and then leave me without my swap partition.
I checked the error with
$ systemctl status mkswap-dev-sdb2.service
× mkswap-dev-sdb2.service - Initialisation of swap device /dev/sdb2
Loaded: loaded (/etc/systemd/system/mkswap-dev-sdb2.service; enabled; preset: enabled)
Active: failed (Result: exit-code) since Fri 2023-02-24 06:52:19 -05; 36min ago
Main PID: 637 (code=exited, status=1/FAILURE)
CPU: 13.137s
Feb 24 06:51:51 ruben mkswap-dev-sdb2-start[653]: dd: error writing '/dev/sdb2': No space left on device
Feb 24 06:52:19 ruben mkswap-dev-sdb2-start[653]: 30518+0 records in
Feb 24 06:52:19 ruben mkswap-dev-sdb2-start[653]: 30517+0 records out
Feb 24 06:52:19 ruben mkswap-dev-sdb2-start[653]: 31999393792 bytes (32 GB, 30 GiB) copied, 295.342 s, 108 MB/s
Feb 24 06:52:19 ruben systemd[1]: mkswap-dev-sdb2.service: Main process exited, code=exited, status=1/FAILURE
Feb 24 06:52:19 ruben systemd[1]: mkswap-dev-sdb2.service: Failed with result 'exit-code'.
Feb 24 06:52:19 ruben systemd[1]: Failed to start Initialisation of swap device /dev/sdb2.
Feb 24 06:52:19 ruben systemd[1]: mkswap-dev-sdb2.service: Consumed 13.137s CPU time, no IP traffic.
Notice: journal has been rotated since unit was started, output may be incomplete.
… where it says “No space left on device”. Fair enough: lowering the size of my swap partition made it work again, but not for long. I lowered from 31997 to 31990 and it worked only until I rebooted again – so maybe it isn’t really about size/disk space.
If it is about the correct size, how do I determine the correct value (and why do my values work until reboot?)
Any idea? Google is awfully quiet on the topic.