Merge pull request #172 from YunoHost-Apps/swap

managing swap

1 files changed, 93 insertions, 0 deletions

diff --git a/scripts/ynh_add_swap b/scripts/ynh_add_swap
new file mode 100644
index 0000000..d7ec44b
--- /dev/null
+++ b/scripts/ynh_add_swap
@@ -0,0 +1,93 @@
+#!/bin/bash
+
+# Add swap
+#
+# usage: ynh_add_swap --size=SWAP in Mb
+# | arg: -s, --size= - Amount of SWAP to add in Mb.
+ynh_add_swap () {
+	# Declare an array to define the options of this helper.
+	declare -Ar args_array=( [s]=size= )
+	local size
+	# Manage arguments with getopts
+	ynh_handle_getopts_args "$@"
+
+	local swap_max_size=$(( $size * 1024 ))
+
+	local free_space=$(df --output=avail / | sed 1d)
+	# Because we don't want to fill the disk with a swap file, divide by 2 the available space.
+	local usable_space=$(( $free_space / 2 ))
+
+ 	SD_CARD_CAN_SWAP=${SD_CARD_CAN_SWAP:-0}
+
+	# Swap on SD card only if it's is specified
+	if ynh_is_main_device_a_sd_card && [ "$SD_CARD_CAN_SWAP" == "0" ]
+	then
+		ynh_print_warn --message="The main mountpoint of your system '/' is on an SD card, swap will not be added to prevent some damage of this one, but that can cause troubles for the app $app. If you still want activate the swap, you can relaunch the command preceded by 'SD_CARD_CAN_SWAP=1'"
+		return
+	fi
+
+	# Compare the available space with the size of the swap.
+	# And set a acceptable size from the request
+	if [ $usable_space -ge $swap_max_size ]
+	then
+		local swap_size=$swap_max_size
+	elif [ $usable_space -ge $(( $swap_max_size / 2 )) ]
+	then
+		local swap_size=$(( $swap_max_size / 2 ))
+	elif [ $usable_space -ge $(( $swap_max_size / 3 )) ]
+	then
+		local swap_size=$(( $swap_max_size / 3 ))
+	elif [ $usable_space -ge $(( $swap_max_size / 4 )) ]
+	then
+		local swap_size=$(( $swap_max_size / 4 ))
+	else
+		echo "Not enough space left for a swap file" >&2
+		local swap_size=0
+	fi
+
+	# If there's enough space for a swap, and no existing swap here
+	if [ $swap_size -ne 0 ] && [ ! -e /swap_$app ]
+	then
+		# Preallocate space for the swap file, fallocate may sometime not be used, use dd instead in this case
+		if ! fallocate -l ${swap_size}K /swap_$app
+		then
+			dd if=/dev/zero of=/swap_$app bs=1024 count=${swap_size}
+		fi
+		chmod 0600 /swap_$app
+		# Create the swap
+		mkswap /swap_$app
+		# And activate it
+		swapon /swap_$app
+		# Then add an entry in fstab to load this swap at each boot.
+		echo -e "/swap_$app swap swap defaults 0 0 #Swap added by $app" >> /etc/fstab
+	fi
+}
+
+ynh_del_swap () {
+	# If there a swap at this place
+	if [ -e /swap_$app ]
+	then
+		# Clean the fstab
+		sed -i "/#Swap added by $app/d" /etc/fstab
+		# Desactive the swap file
+		swapoff /swap_$app
+		# And remove it
+		rm /swap_$app
+	fi
+}
+
+# Check if the device of the main mountpoint "/" is an SD card
+#
+# [internal]
+#
+# return 0 if it's an SD card, else 1
+ynh_is_main_device_a_sd_card () {
+	local main_device=$(lsblk --output PKNAME --noheadings $(findmnt / --nofsroot --uniq --output source --noheadings --first-only))
+
+	if echo $main_device | grep --quiet "mmc" && [ $(tail -n1 /sys/block/$main_device/queue/rotational) == "0" ]
+	then
+		return 0
+	else
+		return 1
+	fi
+}