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First cut of swap image and example
Signed-off-by: Avi Deitcher <avi@deitcher.net> Fix spaces after commas Remove MAINTAINER Signed-off-by: Avi Deitcher <avi@deitcher.net> Simplify swap.yml example to remove files section Signed-off-by: Avi Deitcher <avi@deitcher.net> Switch swap.sh to sh from bash and remove bash from image Signed-off-by: Avi Deitcher <avi@deitcher.net> Replace fallocate with dd and update calculation function to support it Signed-off-by: Avi Deitcher <avi@deitcher.net> Fix indentation Signed-off-by: Avi Deitcher <avi@deitcher.net> Change link to swap to just swap.sh Signed-off-by: Avi Deitcher <avi@deitcher.net> Fix indent Signed-off-by: Avi Deitcher <avi@deitcher.net>
This commit is contained in:
Avi Deitcher
13
pkg/swap/Dockerfile
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13
pkg/swap/Dockerfile
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FROM alpine:3.5
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# swap command - only minimal Alpine install
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# use util-linux to get swapfile utils
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# at some point, hopefully use our own mkswap and swapon
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RUN apk add --update util-linux
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# add the entrypoint and make it executable
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COPY . ./
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# ENTRYPOINT
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ENTRYPOINT swap.sh
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30
pkg/swap/Makefile
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30
pkg/swap/Makefile
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# copy from mount
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.PHONY: tag push clean
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BASE=alpine:3.5
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IMAGE=linuxkit/swap
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default: push
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hash: Dockerfile swap.sh
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DOCKER_CONTENT_TRUST=1 docker pull $(BASE)
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tar cf - $^ | docker build --no-cache -t $(IMAGE):build -
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docker run --rm --entrypoint /bin/sh $(IMAGE):build -c "cat $^ /lib/apk/db/installed | sha1sum" | sed 's/ .*//' > $@
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push: hash
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docker pull $(IMAGE):$(shell cat hash) || \
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(docker tag $(IMAGE):build $(IMAGE):$(shell cat hash) && \
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docker push $(IMAGE):$(shell cat hash))
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docker rmi $(IMAGE):build
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rm -f hash
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tag: hash
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docker pull $(IMAGE):$(shell cat hash) || \
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docker tag $(IMAGE):build $(IMAGE):$(shell cat hash)
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docker rmi $(IMAGE):build
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rm -f hash
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clean:
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rm -f hash
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.DELETE_ON_ERROR:
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85
pkg/swap/README.md
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85
pkg/swap/README.md
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# LinuxKit Swap
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Image to enable creation of a swap file for a [linuxkit](https://github.com/linuxkit/linuxkit)-generated image.
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## Usage
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Normally, unless you are running explicitly in a desktop version, LinuxKit images do not have swap enabled. If you want swap, add the following to your `moby.yml`:
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```
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onboot:
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- name: swap
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image: "linuxkit/swap:1.0.0"
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net: none
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pid: host
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capabilities:
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- CAP_SYS_ADMIN
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readonly: true
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binds:
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- /dev:/dev
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- /var:/var
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command: ["swap.sh","--path","/var/external/swap","--size","2G"]
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```
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Note that you **nust** mount the following:
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* `/var` to `/var` so it can place the swapfile in the right location.
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* `/dev` to `/dev` so it can do the right thing for devices
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### Options
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Options are passed to it via command-line options. The following are the options. Details follow.
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|Option|Parameter|Default|Required|Notes|
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|---|---|---|---|---|
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|`--path`|Path to file as seen in the underlying OS||**Yes**||
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|`--size`|Target swapfile size||**Yes**||
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|`--condition`|_condition_||No|Condition that must be met to create a swapfile|
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|`--debug`||No|Turns on verbose output from the command making the swap|
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#### File
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You can create a swapfile at the given path. You **must** provide exactly one swapfile path, or none will be created; there is no default. Passing fewer than or more than one `--path` option causes the container to exit with an error.
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The option `--path` takes a single argument _path_, path to the swapfile, e.g. `/var/mnt/swap2`.
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You **always** should put the swap file somewhere under `/var`, since that is where read-writable files and mounts exist in linuxkit images.
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#### Size
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`--size <size>` indicates the desired swapfile size, e.g. `2G` `100M` `5670K` `8765432`. There is no default. Acceptable size units are `G`, `M`, `K` and bytes of no unit provided.
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If disk space on the requested partition is insufficient to create the swapfile, the container exits with an error.
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#### Conditions
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You may want to create a swapfile only if certain conditions are met. Supported conditions are:
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* An external disk is available
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* Partition on which the swapfile will sit is of a minimum size.
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**All** conditions must be met. If a condition fails, the swapfile is not created, but the container exits with no error, unless you set the condition as `required`.
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Conditions are structured as follows: _type_:_parameter_:_required_
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In all cases, you may leave off _required_ if you wish to treat it as false, i.e. do not create swapfile but exit with no error if the condition is not met.
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##### Partition exists
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LinuxKit may be running from a small disk, and you only want to run if a particular large external disk is available. In that case, pass `--condition part:<path>:<required>` to indicate that swapfile is to be created only if _path_ already exists and is a mount point.
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Example: `--condition part:/var/mnt/external`
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##### Size
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You may set a minimum size for a partition (likely the one on which the swapfile will be created) using the `size` condition of the format `--condition size:<path>:<size>:<required>` to indicate that swapfile is to be created only if the partition on which _path_ exists is of minimum size _size_. Acceptable sizes are identical to those for the swapfile.
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Examples:
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* `--condition partsize:/var/mnt/external:100G:true`
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## Example
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An example yml file is included in [examples/swap.yml](../../examples/swap.yml). `swap.yml`. Note that you need to attach an external disk - trying to create a swapfile in tmpfs `/var` will fail.
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The sample command to run the enclosed is:
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```
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moby build swap.yml
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moby run -disk-size 4096 swap
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```
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135
pkg/swap/swap.sh
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135
pkg/swap/swap.sh
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#!/bin/sh
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set -e
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while [ $# -gt 1 ]; do
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key="$1"
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case $key in
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--debug)
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set -x
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;;
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--path)
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path="$2"
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shift # past argument
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;;
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--size)
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size="$2"
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shift # past argument
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;;
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--encrypt)
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ENCRYPT=true
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;;
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--condition)
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CONDITIONS="$CONDITIONS $2"
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shift
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;;
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*)
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echo "Unknown option passed to swapmaker: $key" # unknown option
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exit 1
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;;
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esac
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shift # past argument or value
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done
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function disksize_to_count {
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local blocksize=$1
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local origsize=$2
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local ret
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case $origsize in
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*G)
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ret=$(( ${origsize%%G} * 1024 * 1024 * 1024 ))
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;;
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*M)
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ret=$(( ${origsize%%M} * 1024 * 1024 ))
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;;
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*K)
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ret=$(( ${origsize%%K} * 1024 ))
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;;
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*)
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ret=$origsize
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;;
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esac
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ret=$(( $ret / $blocksize ))
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echo $ret
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}
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## make sure path is valid
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if [ -z "${path}" ]; then
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echo "swap: --file <path> must be defined"
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exit 1
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fi
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if [ "${path:0:5}" != "/var/" -o ${#path} -lt 6 ]; then
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echo "--file <path> option must be under /var"
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exit 1
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fi
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if [ -z "${size}" ]; then
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echo "swap: --size <size> must be defined"
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exit 1
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fi
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## check each of our conditions
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for cond in $CONDITIONS; do
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# split the condition parts
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IFS=: read condtype arg1 arg2 arg3 arg4 <<< "$cond"
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case $condtype in
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part)
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partition=$arg1
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required=$arg2
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# check that the path exists as its own mount point
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set +e
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grep -qs $partition /proc/mounts
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is_mnt=$?
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set -e
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if [ $is_mnt -ne 0 ]; then
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[ "$required" == "true" ] && exit 1
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exit 0
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fi
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;;
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partsize)
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partition=$arg1
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minsize=$arg2
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required=$arg3
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# check that the partition on which it exists has sufficient size
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partsize=$(df -k $partition | tail -1 | awk '{print $2}')
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partsize=$(( $partsize * 1024 ))
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# convert minsize to bytes
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minsize=$(disksize_to_count 1 $minsize)
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if [ $partsize -lt $minsize ]; then
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[ "$required" == "true" ] && exit 1
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exit 0
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fi
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;;
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*)
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echo "Unknown condition: $cond"
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exit 1
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;;
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esac
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done
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## if a condition failed:
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### Required? exit 1
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### Else? exit 0
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## Allocate the file
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dd if=/dev/zero of=$path bs=1024 count=$(disksize_to_count 1024 $size)
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chmod 0600 $path
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## was it encrypted? use cryptsetup and get the mapped device
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if [ "$ENCRYPT" == "true" ]; then
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# might need
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#loop=$(losetup -f)
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#losetup ${loop} ${path}
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cryptsetup open --type plain --key-file /dev/urandom --key-size=256 --hash=sha256 --cipher=aes-cbc-essiv --offset=0 ${path} swapfile
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SWAPDEV=/dev/mapper/swapfile
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else
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SWAPDEV=$path
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fi
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## mkswap and swapon the device
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/sbin/mkswap $SWAPDEV
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/sbin/swapon $SWAPDEV
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