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glitchsoc_ynh/scripts/ynh_add_swap
2024-03-27 17:43:18 +01:00

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#!/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
}