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tests: Implemented volume state safety tests
Implemented tests for behavior when mount and unmount operations partially fail (in those cases, docker-on-top must detect that and either refuse to mount the volume, refuse to mount the volume on the next attempt, or recover on the next attempt, but not bring the volume to an unsafe state). + extracted a common part from basic_usage.bats to common.sh
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+225
-17
lines changed

3 files changed

+225
-17
lines changed

‎tests/basic_usage.bats‎

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#!/usr/bin/env bats
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# For `CONTAINER_CMD_*`
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load common.sh
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basic_test() {
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# Setup
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BASE="$(mktemp --directory)"
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echo 456 > "$BASE"/b
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docker run --rm -v "$NAME":/dot alpine:latest \
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sh -e -c '
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# Initial data is visible
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[ "$(cat /dot/a)" = 123 ]
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[ "$(cat /dot/b)" = 456 ]
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# My file removal is visible to me
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rm /dot/a
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[ ! -e /dot/a ]
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# My changes are visible to me
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echo 789 > /dot/b
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[ "$(cat /dot/b)" = 789 ]
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# My new files are visible to me
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echo etc > /dot/c
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[ "$(cat /dot/c)" = etc ]
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'
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sh -e -c "
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$CONTAINER_CMD_CHECK_INITIAL_DATA
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$CONTAINER_CMD_MAKE_AND_CHECK_CHANGES
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"
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# Changes are not visible from the host
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[ "$(cat "$BASE"/a)" = 123 ]

‎tests/common.sh‎

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#!/bin/false
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CONTAINER_CMD_CHECK_INITIAL_DATA='
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# Check that the initial data is as expected
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[ "$(cat /dot/a)" = 123 ]
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[ "$(cat /dot/b)" = 456 ]
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'
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CONTAINER_CMD_MAKE_AND_CHECK_CHANGES='
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# My file removal is visible to me
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rm -f /dot/a
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[ ! -e /dot/a ]
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# My changes are visible to me
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echo 789 > /dot/b
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[ "$(cat /dot/b)" = 789 ]
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# My new files are visible to me
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echo etc > /dot/c
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[ "$(cat /dot/c)" = etc ]
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'
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CONTAINER_CMD_CHECK_ALREADY_MODIFIED_DATA='
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[ ! -e /dot/a ]
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[ "$(cat /dot/b)" = 789 ]
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[ "$(cat /dot/c)" = etc ]
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'

‎tests/mounted_volume_state_safety.bats‎

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#!/usr/bin/env bats
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# TODO: move the following explanation from here to the source code?
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# Under normal operation, docker-on-top keeps all of its volumes in a
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# _valid_ state. When interfered with (e.g., when the user messes with
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# our internal state or in case we were terminated abruptly or whatever
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# other reason causes our crucial syscalls to fail),
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# it may not be possible to maintain a _valid_ state, but we still want to
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# leave a volume in a state that is _safe_, that is, on the next interaction
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# with the volume, docker-on-top can tell that something went wrong last time.
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# For example, if a volume is unmounted improperly, such that `activemountsdir`
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# was cleaned properly but we failed to unmount `mountpointdir`, that's unfortunate
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# (as we leave a mount hanging) but tolerable (as the next attempt to mount it will
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# succeed as if the volume was unmounted cleanly).
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#
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# On the contrary, if a volume is unmounted improperly, such that `mountpointdir`
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# was unmounted but `activemountsdir` remains non-empty, that's a horror. On the
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# next attempt to mount that volume, docker-on-top will see that it is already mounted
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# and will try to use `mountpoindir` outright but, as it is not actually mounted, that
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# will lead to a completely broken behavior.
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# The following tests try to simulate that either mount/unmount system calls, or
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# activemounts file creation/removal system calls fail, and tests that docker-on-top
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# is fine.
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# For `CONTAINER_CMD_*`
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load common.sh
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# Ask for password early
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sudo -v
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# Test template
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# $1 is empty if volatile, non-empty if non-volatile;
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# $2 is the command (messing with the state) to perform before mounting;
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# $3 is the command (messing with the state) to perform before unmounting;
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# $4 shall undo the effect of $2;
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# $5 shall undo the effect of $3.
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template() {
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# Setup
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BASE="$(mktemp --directory)"
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NAME="$(basename "$BASE")"
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if [ -z "$1" ]; then
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VOLATILE=false
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else
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VOLATILE=true
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fi
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docker volume create --driver docker-on-top "$NAME" -o base="$BASE" -o volatile="$VOLATILE"
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echo 123 > "$BASE"/a
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echo 456 > "$BASE"/b
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# Run the breaking action before mount
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$2 "$BASE" "$NAME"
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# Start the container (might fail)
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if ! CONTAINER_ID=$(
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docker run -d -v "$NAME":/dot alpine:latest \
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sh -e -c "
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sleep 1 # Give as a moment to break everything
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$CONTAINER_CMD_CHECK_INITIAL_DATA
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$CONTAINER_CMD_MAKE_AND_CHECK_CHANGES
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"
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); then
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# If it has failed, we are most lucky: docker-on-top has detected the problem
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# so early it did not break anything in the first place
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true; return
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fi
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# Undo the breaking action
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$4 "$BASE" "$NAME"
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# Run the breaking action before unmount
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$3 "$BASE" "$NAME"
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if [ 0 -ne "$(docker wait "$CONTAINER_ID")" ]; then
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# Container has failed
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docker rm "$CONTAINER_ID"
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false
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return
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fi
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docker rm "$CONTAINER_ID"
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# Undo the breaking action
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$5 "$BASE" "$NAME"
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# Now that we are fixed, we expect that either the container won't stat at all:
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if ! docker run --rm -v "$NAME":/dot alpine:latest true; then
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return # The test is successful: docker-on-top detected the error and the mount is refused
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fi
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# Or a container should start and run as expected:
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if $VOLATILE; then
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docker run --rm -v "$NAME":/dot alpine:latest \
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sh -e -c "
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$CONTAINER_CMD_CHECK_INITIAL_DATA
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$CONTAINER_CMD_MAKE_AND_CHECK_CHANGES
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"
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else
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docker run --rm -v "$NAME":/dot alpine:latest \
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sh -e -c "
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$CONTAINER_CMD_CHECK_ALREADY_MODIFIED_DATA
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$CONTAINER_CMD_MAKE_AND_CHECK_CHANGES
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"
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fi
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# Cleanup (also help docker-on-top with what we may have broken)
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sudo umount /var/lib/docker-on-top/"$NAME"/mountpoint || :
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sudo rmdir /var/lib/docker-on-top/"$NAME"/mountpoint || :
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sudo rm /var/lib/docker-on-top/"$NAME"/activemounts/* || :
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rm -rf "$BASE"
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docker volume rm "$NAME"
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}
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# I use "activate"/"deactivate" as shorts for "create/remove a file at `activemountsdir`"
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# Break/unbreak functions receive $BASE as $1 and $NAME as $2
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break_deactivate() {
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# Immutable file can not be removed
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sudo chattr +i /var/lib/docker-on-top/"$2"/activemounts/*
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}
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unbreak_deactivate() {
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sudo chattr -i /var/lib/docker-on-top/"$2"/activemounts/*
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}
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@test "Mount=fine, activate=fine, unmount=fine, deactivate=broken" {
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template "" : : break_deactivate unbreak_deactivate
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template "volatile" : : break_deactivate unbreak_deactivate
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}
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break_unmount() {
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# The mountpoint will be kept busy with the following process that has a file on it open
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sleep 1.5 < /var/lib/docker-on-top/"$2"/mountpoint/b
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}
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unbreak_unmount() {
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# Just wait for the previous process to finish
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sleep 1.5
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}
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@test "Mount=fine, activate=fine, unmount=broken, deactivate=fine" {
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skip "This is not working yet, needs to be fixed"
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template "" : : break_unmount unbreak_unmount
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template "volatile" : : break_unmount unbreak_unmount
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}
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break_activate() {
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sudo chattr +i /var/lib/docker-on-top/"$2"/activemounts
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}
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unbreak_activate() {
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sudo chattr -i /var/lib/docker-on-top/"$2"/activemounts
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}
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@test "Mount=fine, activate=broken, unmount=fine, deactivate=fine" {
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template "" break_activate unbreak_activate : :
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template "volatile" break_activate unbreak_activate : :
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}
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break_mount() {
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# If the base directory does not exist, the overlayfs mount shall fail
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rm -r "$1"
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}
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unbreak_mount() {
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mkdir "$1"
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}
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@test "Mount=broken, activate=fine, unmount=fine, deactivate=fine" {
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template "" break_mount unbreak_mount : :
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template "volatile" break_mount unbreak_mount : :
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}

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