From b30852ed41f7e6729de9a75a71a671ce7d03dff9 Mon Sep 17 00:00:00 2001 From: Bjørn Forsman Date: Wed, 6 Jul 2016 13:41:40 +0200 Subject: nixos/swap: support for resizing swapfile Currently NixOS creates the swapfile (with the specified size) only if it doesn't already exist. Changing the swapfile size afterwards will not have any effect. This commit changes that so the swapfile will be recreated whenever swapDevices.*.size is changed (or more precisely, whenever the actual file size differs from the configured one), allowing both growing and shrinking the swapfile. The service unit has "restartIfChanged = false", so we don't have to worry about the swapfile being in use at the time this code is run (you have to reboot for swapfile changes). fallocate doesn't shrink files, use truncate for that. truncate can also be used to grow files, but it creates "holes" in the file which doesn't work with swapfiles. --- nixos/modules/config/swap.nix | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'nixos/modules/config/swap.nix') diff --git a/nixos/modules/config/swap.nix b/nixos/modules/config/swap.nix index f0353c5a35ec..62b6e011713e 100644 --- a/nixos/modules/config/swap.nix +++ b/nixos/modules/config/swap.nix @@ -30,8 +30,7 @@ let description = '' If this option is set, ‘device’ is interpreted as the path of a swapfile that will be created automatically - with the indicated size (in megabytes) if it doesn't - exist. + with the indicated size (in megabytes). ''; }; @@ -132,9 +131,13 @@ in script = '' ${optionalString (sw.size != null) '' - if [ ! -e "${sw.device}" ]; then + currentSize=$(( $(stat -c "%s" "${sw.device}" 2>/dev/null || echo 0) / 1024 / 1024 )) + if [ "${toString sw.size}" != "$currentSize" ]; then fallocate -l ${toString sw.size}M "${sw.device}" || dd if=/dev/zero of="${sw.device}" bs=1M count=${toString sw.size} + if [ "${toString sw.size}" -lt "$currentSize" ]; then + truncate --size "${toString sw.size}M" "${sw.device}" + fi chmod 0600 ${sw.device} ${optionalString (!sw.randomEncryption) "mkswap ${sw.realDevice}"} fi -- cgit 1.4.1