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Setting db_persist is required for dm devices so that their properties are carried over on switch-root from the initrd to the rootfs. This logic has always lived in dracut (https://github.com/dracutdevs/dracut/blob/master/modules.d/90dm/11-dm.rules). However, this means that other initramfs generators each have to implement and maintain the same rule which leads to unnecessary duplication. Instead, let's make the rule part of the upstream lvm rules, which will ensure that generated initramfses will just work if they make sure the lvm udev rules are installed, without having to figure out that they have to add an extra rule themselves on top. Identical rule in Arch Linux's lvm2 package: https://gitlab.archlinux.org/archlinux/packaging/packages/lvm2/-/blob/main/11-dm-initramfs.rules?ref_type=heads
175 lines
8.3 KiB
Plaintext
175 lines
8.3 KiB
Plaintext
# Copyright (C) 2009 Red Hat, Inc. All rights reserved.
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#
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# This file is part of LVM2.
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# Udev rules for device-mapper devices.
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#
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# These rules create a DM control node in /dev/(DM_DIR) directory.
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# The rules also create nodes named dm-x (x is a number) in /dev
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# directory and symlinks to these nodes with names given by
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# the actual DM names. Some udev environment variables are set
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# for use in later rules:
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# DM_NAME - actual DM device's name
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# DM_UUID - UUID set for DM device (blank if not specified)
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# DM_UDEV_RULES_VSN - DM udev rules version
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# DM_UDEV_DISABLE_OTHER_RULES_FLAG - a flag that indicates that
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# stacked layers shouldn't attempt to probe the device, and
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# should try to import relevant properties from the udev db.
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#
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# These rules cover only basic device-mapper functionality in udev.
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#
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# Various DM subsystems may contain further subsystem-specific rules
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# in 11-dm-<subsystem_name>.rules which should be installed together
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# with the DM subsystem and which extend these basic rules.
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# For example:
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# 11-dm-lvm.rules for LVM subsystem
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# 11-dm-mpath.rules for multipath subsystem (since version 0.6.0, recommended!)
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#
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# 11-dm<subsystem_name>.rules may use other DM related properties besides
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# those listed above, like .DM_SUSPENDED. These properties are considered
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# internal to device mapper, and subject to change without notice.
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# Rules that are executed after 13-dm-disk.rules shouldn't use them.
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#
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# Even more specific rules may be required by subsystems so always
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# check subsystem's upstream repository for recent set of rules.
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# Also, keep in mind that recent rules may also require recent
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# subsystem-specific binaries.
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SUBSYSTEM!="block", GOTO="dm_end"
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KERNEL!="dm-[0-9]*", GOTO="dm_end"
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(DM_EXEC_RULE)
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# Device created, major and minor number assigned - "add" event generated.
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# Table loaded - no event generated.
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# Device resumed (or renamed) - "change" event generated.
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# Device removed - "remove" event generated.
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#
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# The dm-X nodes are always created, even on "add" event, we can't suppress
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# that (the node is created even earlier with devtmpfs). All the symlinks
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# (e.g. /dev/mapper) are created in right time after a device has its table
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# loaded and is properly resumed. For this reason, direct use of dm-X nodes
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# is not recommended.
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ACTION=="remove", GOTO="dm_end"
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# Persist device state on transition from the initrd. This means all udev device
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# properties are kept in the udev database even when it is cleaned up on
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# switch-root.
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OPTIONS+="db_persist"
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# Decode udev control flags and set environment variables appropriately.
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# These flags are encoded in DM_COOKIE variable that was introduced in
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# kernel version 2.6.31. Therefore, we can use this feature with
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# kernels >= 2.6.31 only. Cookie is not decoded for remove event.
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ENV{DM_COOKIE}!="?*", GOTO="dm_no_cookie"
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IMPORT{program}="(DM_EXEC)/dmsetup udevflags $env{DM_COOKIE}"
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# Store the original flag from the cookie as DM_COOKIE_DISABLE_OTHER_RULES_FLAG
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# in the udev db. DM_UDEV_DISABLE_OTHER_RULES_FLAG will be or'd with other
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# conditions for use by upper, non-dm layers.
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ENV{DM_COOKIE_DISABLE_OTHER_RULES_FLAG}="$env{DM_UDEV_DISABLE_OTHER_RULES_FLAG}"
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LABEL="dm_no_cookie"
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# There is no cookie set nor any flags encoded in events not originating
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# in libdevmapper so we need to detect this and try to behave correctly.
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# For such spurious events, regenerate all flags from current udev database content
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# (this information would normally be inaccessible for spurious ADD and CHANGE events).
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ENV{DM_UDEV_PRIMARY_SOURCE_FLAG}=="1", ENV{DM_ACTIVATION}="1", GOTO="dm_flags_done"
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IMPORT{db}="DM_UDEV_DISABLE_DM_RULES_FLAG"
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IMPORT{db}="DM_UDEV_DISABLE_SUBSYSTEM_RULES_FLAG"
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IMPORT{db}="DM_UDEV_DISABLE_DISK_RULES_FLAG"
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IMPORT{db}="DM_COOKIE_DISABLE_OTHER_RULES_FLAG"
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IMPORT{db}="DM_UDEV_LOW_PRIORITY_FLAG"
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IMPORT{db}="DM_UDEV_DISABLE_LIBRARY_FALLBACK_FLAG"
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IMPORT{db}="DM_UDEV_PRIMARY_SOURCE_FLAG"
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IMPORT{db}="DM_UDEV_FLAG7"
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IMPORT{db}="DM_UDEV_RULES_VSN"
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ENV{DM_UDEV_DISABLE_OTHER_RULES_FLAG}="$env{DM_COOKIE_DISABLE_OTHER_RULES_FLAG}"
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LABEL="dm_flags_done"
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# If DISK_RO is set, it's an uevent that changes the ro attribute of the device.
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# The event should be ignored as far as dm is concerned.
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ENV{DISK_RO}=="0|1", GOTO="dm_disable"
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# Normally, we operate on "change" events. But when coldplugging, there's an
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# "add" event present. We have to recognize this and do our actions in this
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# particular situation, too. Also, we don't want the nodes to be created
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# prematurely on "add" events while not coldplugging. We check
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# DM_UDEV_PRIMARY_SOURCE_FLAG to see if the device was activated correctly
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# before and if not, we ignore the "add" event totally. This way we can support
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# udev triggers generating "add" events (e.g. "udevadm trigger --action=add" or
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# "echo add > /sys/block/<dm_device>/uevent"). The trigger with "add" event is
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# also used at boot to reevaluate udev rules for all existing devices activated
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# before (e.g. in initrd). If udev is used in initrd, we require the udev init
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# script to not remove the existing udev database so we can reuse the information
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# stored at the time of device activation in the initrd.
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ACTION!="add", GOTO="dm_no_coldplug"
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ENV{DM_UDEV_RULES_VSN}!="1", ENV{DM_UDEV_PRIMARY_SOURCE_FLAG}!="1", GOTO="dm_disable"
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ENV{DM_ACTIVATION}="1"
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LABEL="dm_no_coldplug"
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# Putting it together, following table is used to recognize genuine and spurious events.
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# N.B. Spurious events are generated based on use of the WATCH udev
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# rule or by triggering an event manually by "udevadm trigger" call
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# or by "echo <event_name> > /sys/block/dm-X/uevent".
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#
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# EVENT DM_UDEV_PRIMARY_SOURCE_FLAG DM_ACTIVATION
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# ======================================================================
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# add event (genuine) 0 0
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# change event (genuine) 1 1
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# add event (spurious)
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# |_ dev still not active 0 0
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# \_ dev already active 1 1
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# change event (spurious)
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# |_ dev still not active 0 0
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# \_ dev already active 1 0
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# "dm" sysfs subdirectory is available in newer versions of DM
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# only (kernels >= 2.6.29). We have to check for its existence
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# and use dmsetup tool instead to get the DM name, uuid and
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# suspended state if the "dm" subdirectory is not present.
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# The "suspended" item was added even later (kernels >= 2.6.31),
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# so we also have to call dmsetup if the kernel version used
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# is in between these releases.
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TEST=="dm", ENV{DM_NAME}="$attr{dm/name}", ENV{DM_UUID}="$attr{dm/uuid}", ENV{.DM_SUSPENDED}="$attr{dm/suspended}"
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TEST!="dm", IMPORT{program}="(DM_EXEC)/dmsetup info -j %M -m %m -c --nameprefixes --noheadings --rows -o name,uuid,suspended"
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ENV{.DM_SUSPENDED}=="?*", GOTO="dm_suspended_set"
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TEST=="dm", IMPORT{program}="(DM_EXEC)/dmsetup info -j %M -m %m -c --nameprefixes --noheadings --rows -o suspended"
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# dmsetup tool provides suspended state information in textual
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# form with values "Suspended"/"Active". We translate it to
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# 0/1 respectively to be consistent with sysfs values.
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ENV{DM_SUSPENDED}=="Active", ENV{.DM_SUSPENDED}="0"
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ENV{DM_SUSPENDED}=="Suspended", ENV{.DM_SUSPENDED}="1"
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ENV{DM_SUSPENDED}=""
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LABEL="dm_suspended_set"
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# This variable provides a reliable way to check that device-mapper
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# rules were installed. It means that all needed variables are set
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# by these rules directly so there's no need to acquire them again
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# later. Other rules can alternate the functionality based on this
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# fact (e.g. fallback to rules that behave correctly even without
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# these rules installed). It also provides versioning for any
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# possible future changes.
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# VSN 1 - original rules
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# VSN 2 - add support for synthesized events
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# VSN 3 - use DM_UDEV_DISABLE_OTHER_RULES_FLAG as the only "API"
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# to be consumed by non-dm rules.
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ENV{DM_UDEV_RULES_VSN}="3"
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ENV{DM_UDEV_DISABLE_DM_RULES_FLAG}!="1", ENV{DM_NAME}=="?*", SYMLINK+="(DM_DIR)/$env{DM_NAME}"
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# Avoid processing and scanning a DM device in the other (foreign)
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# rules if it is in suspended state. However, we still keep 'disk'
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# and 'DM subsystem' related rules enabled in this case.
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ENV{.DM_SUSPENDED}=="1", ENV{DM_UDEV_DISABLE_OTHER_RULES_FLAG}="1"
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GOTO="dm_end"
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LABEL="dm_disable"
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ENV{DM_UDEV_DISABLE_SUBSYSTEM_RULES_FLAG}="1"
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ENV{DM_UDEV_DISABLE_DISK_RULES_FLAG}="1"
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ENV{DM_UDEV_DISABLE_OTHER_RULES_FLAG}="1"
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OPTIONS:="nowatch"
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LABEL="dm_end"
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