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.\"     Title: criu
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 06/01/2018
.\"    Manual: CRIU Manual
.\"    Source: criu 3.9
.\"  Language: English
.\"
.TH "CRIU" "8" "06/01/2018" "criu 3\&.9" "CRIU Manual"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
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.\" -----------------------------------------------------------------
.\" * (re)Define some macros
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..
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.\}
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.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "Name"
criu \- checkpoint/restore in userspace
.SH "Synopsis"
.sp
\fBcriu\fR \fIcommand\fR [\fIoption\fR \&...]
.SH "DESCRIPTION"
.sp
\fBcriu\fR is a tool for checkpointing and restoring running applications\&. It does this by saving their state as a collection of files (see the \fBdump\fR command) and creating equivalent processes from those files (see the \fBrestore\fR command)\&. The restore operation can be performed at a later time, on a different system, or both\&.
.SH "OPTIONS"
.sp
Most of the true / false long options (the ones without arguments) can be prefixed with \fB\-\-no\-\fR to negate the option (example: \fB\-\-display\-stats\fR and \fB\-\-no\-display\-stats\fR)\&.
.SS "Common options"
.sp
Common options are applicable to any \fIcommand\fR\&.
.PP
\fB\-v\fR[\fBv\fR\&...], \fB\-\-verbosity\fR
.RS 4
Increase verbosity up from the default level\&. Multiple
\fBv\fR
can be used, each increasing verbosity by one level\&. Using long option without argument increases verbosity by one level\&.
.RE
.PP
\fB\-v\fR\fInum\fR, \fB\-\-verbosity\fR=\fInum\fR
.RS 4
Set verbosity level to
\fInum\fR\&. The higher the level, the more output is produced\&.

The following levels are available:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-v0\fR
no output;
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-v1\fR
only errors;
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-v2\fR
above plus warnings (this is the default level);
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-v3\fR
above plus information messages and timestamps;
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fB\-v4\fR
above plus lots of debug\&.
.RE
.RE
.PP
\fB\-\-pidfile\fR \fIfile\fR
.RS 4
Write root task, service or page\-server pid into a
\fIfile\fR\&.
.RE
.PP
\fB\-o\fR, \fB\-\-log\-file\fR \fIfile\fR
.RS 4
Write logging messages to
\fIfile\fR\&.
.RE
.PP
\fB\-\-log\-pid\fR
.RS 4
Write separate logging files per each pid\&.
.RE
.PP
\fB\-\-display\-stats\fR
.RS 4
During dump as well as during restore
\fBcriu\fR
collects information like the time required to dump or restore the process or the number of pages dumped or restored\&. This information is always written to the files
\fIstats\-dump\fR
and
\fIstats\-restore\fR
and can be easily displayed using
\fBcrit\fR\&. The option
\fB\-\-display\-stats\fR
additionally prints out this information on the console at the end of a dump or a restore\&.
.RE
.PP
\fB\-D\fR, \fB\-\-images\-dir\fR \fIpath\fR
.RS 4
Use
\fIpath\fR
as a base directory where to look for sets of image files\&.
.RE
.PP
\fB\-\-prev\-images\-dir\fR \fIpath\fR
.RS 4
Use
\fIpath\fR
as a parent directory where to look for sets of image files\&. This option makes sense in case of incremental dumps\&.
.RE
.PP
\fB\-W\fR, \fB\-\-work\-dir\fR \fIdir\fR
.RS 4
Use directory
\fIdir\fR
for putting logs, pidfiles and statistics\&. If not specified,
\fIpath\fR
from
\fB\-D\fR
option is taken\&.
.RE
.PP
\fB\-\-close\fR \fIfd\fR
.RS 4
Close file descriptor
\fIfd\fR
before performing any actions\&.
.RE
.PP
\fB\-L\fR, \fB\-\-libdir\fR \fIpath\fR
.RS 4
Path to plugins directory\&.
.RE
.PP
\fB\-\-action\-script\fR \fIscript\fR
.RS 4
Add an external action script to be executed at certain stages\&. The environment variable
\fBCRTOOLS_SCRIPT_ACTION\fR
is available to the script to find out which action is being executed, and its value can be one of the following:
.PP
\fBpre\-dump\fR
.RS 4
run prior to beginning a
\fBdump\fR
.RE
.PP
\fBpost\-dump\fR
.RS 4
run upon
\fBdump\fR
completion
.RE
.PP
\fBpre\-restore\fR
.RS 4
run prior to beginning a
\fBrestore\fR
.RE
.PP
\fBpre\-resume\fR
.RS 4
run when all processes and resources are restored but tasks are stopped waiting for final kick to run\&. Must not fail\&.
.RE
.PP
\fBpost\-restore\fR
.RS 4
run upon
\fBrestore\fR
completion
.RE
.PP
\fBnetwork\-lock\fR
.RS 4
run to lock network in a target network namespace
.RE
.PP
\fBnetwork\-unlock\fR
.RS 4
run to unlock network in a target network namespace
.RE
.PP
\fBsetup\-namespaces\fR
.RS 4
run once root task just been created with required namespaces\&. Note it is an early stage of restore, when nothing is restored yet except for namespaces themselves
.RE
.RE
.PP
\fB\-V\fR, \fB\-\-version\fR
.RS 4
Print program version and exit\&.
.RE
.PP
\fB\-h\fR, \fB\-\-help\fR
.RS 4
Print some help and exit\&.
.RE
.SS "pre\-dump"
.sp
Performs the pre\-dump procedure, during which \fBcriu\fR creates a snapshot of memory changes since the previous \fBpre\-dump\fR\&. Note that during this \fBcriu\fR also creates the fsnotify cache which speeds up the \fBrestore\fR procedure\&. \fBpre\-dump\fR requires at least \fB\-t\fR option (see \fBdump\fR below)\&. In addition, \fBpage\-server\fR options may be specified\&.
.PP
\fB\-\-track\-mem\fR
.RS 4
Turn on memory changes tracker in the kernel\&. If the option is not passed the memory tracker get turned on implicitly\&.
.RE
.SS "dump"
.sp
Performs a checkpoint procedure\&.
.PP
\fB\-t\fR, \fB\-\-tree\fR \fIpid\fR
.RS 4
Checkpoint the whole process tree starting from
\fIpid\fR\&.
.RE
.PP
\fB\-R\fR, \fB\-\-leave\-running\fR
.RS 4
Leave tasks in running state after checkpoint, instead of killing\&. This option is pretty dangerous and should be used only if you understand what you are doing\&.
.sp
Note if task is about to run after been checkpointed, it can modify TCP connections, delete files and do other dangerous actions\&. Therefore,
\fBcriu\fR
can not guarantee that the next
\fBrestore\fR
action will succeed\&. Most likely if this option is used, at least the file system snapshot must be made with the help of
\fBpost\-dump\fR
action script\&.
.sp
In other words, do not use it unless really needed\&.
.RE
.PP
\fB\-s\fR, \fB\-\-leave\-stopped\fR
.RS 4
Leave tasks in stopped state after checkpoint, instead of killing\&.
.RE
.PP
\fB\-\-external\fR \fItype\fR\fB[\fR\fIid\fR\fB]:\fR\fIvalue\fR
.RS 4
Dump an instance of an external resource\&. The generic syntax is
\fItype\fR
of resource, followed by resource
\fIid\fR
(enclosed in literal square brackets), and optional
\fIvalue\fR
(prepended by a literal semicolon)\&. The following resource types are currently supported:
\fBmnt\fR,
\fBdev\fR,
\fBfile\fR,
\fBtty\fR,
\fBunix\fR\&. Syntax depends on type\&. Note to restore external resources, either
\fB\-\-external\fR
or
\fB\-\-inherit\-fd\fR
is used, depending on resource type\&.
.RE
.PP
\fB\-\-external mnt[\fR\fImountpoint\fR\fB]:\fR\fIname\fR
.RS 4
Dump an external bind mount referenced by
\fImountpoint\fR, saving it to image under the identifier
\fIname\fR\&.
.RE
.PP
\fB\-\-external mnt[]:\fR\fIflags\fR
.RS 4
Dump all external bind mounts, autodetecting those\&. Optional
\fIflags\fR
can contain
\fBm\fR
to also dump external master mounts,
\fBs\fR
to also dump external shared mounts (default behavior is to abort dumping if such mounts are found)\&. If
\fIflags\fR
are not provided, semicolon is optional\&.
.RE
.PP
\fB\-\-external dev[\fR\fImajor\fR\fB/\fR\fIminor\fR\fB]:\fR\fIname\fR
.RS 4
Allow to dump a mount namespace having a real block device mounted\&. A block device is identified by its
\fImajor\fR
and
\fIminor\fR
numbers, and
\fBcriu\fR
saves its information to image under the identifier
\fIname\fR\&.
.RE
.PP
\fB\-\-external file[\fR\fImnt_id\fR\fB:\fR\fIinode\fR\fB]\fR
.RS 4
Dump an external file, i\&.e\&. an opened file that is can not be resolved from the current mount namespace, which can not be dumped without using this option\&. The file is identified by
\fImnt_id\fR
(a field obtained from
\fB/proc/\fR\fIpid\fR\fB/fdinfo/\fR\fIN\fR) and
\fIinode\fR
(as returned by
\fBstat\fR(2))\&.
.RE
.PP
\fB\-\-external tty[\fR\fIrdev\fR\fB:\fR\fIdev\fR\fB]\fR
.RS 4
Dump an external TTY, identified by
\fBst_rdev\fR
and
\fBst_dev\fR
fields returned by
\fBstat\fR(2)\&.
.RE
.PP
\fB\-\-external unix[\fR\fIid\fR\fB]\fR
.RS 4
Tell
\fBcriu\fR
that one end of a pair of UNIX sockets (created by
\fBsocketpair\fR(2)) with
\fIid\fR
is OK to be disconnected\&.
.RE
.PP
\fB\-\-freeze\-cgroup\fR
.RS 4
Use cgroup freezer to collect processes\&.
.RE
.PP
\fB\-\-manage\-cgroups\fR
.RS 4
Collect cgroups into the image thus they gonna be restored then\&. Without this option,
\fBcriu\fR
will not save cgroups configuration associated with a task\&.
.RE
.PP
\fB\-\-cgroup\-props\fR \fIspec\fR
.RS 4
Specify controllers and their properties to be saved into the image file\&.
\fBcriu\fR
predefines specifications for common controllers, but since the kernel can add new controllers and modify their properties, there should be a way to specify ones matched the kernel\&.
.sp
\fIspec\fR
argument describes the controller and properties specification in a simplified YAML form:
.sp
.if n \{\
.RS 4
.\}
.fam C
.ps -1
.nf
.BB lightgray
"c1":
 \- "strategy": "merge"
 \- "properties": ["a", "b"]
"c2":
 \- "strategy": "replace"
 \- "properties": ["c", "d"]
.EB lightgray
.fi
.fam
.ps +1
.if n \{\
.RE
.\}
.sp
where
\fIc1\fR
and
\fIc2\fR
are controllers names, and
\fIa\fR,
\fIb\fR,
\fIc\fR,
\fId\fR
are their properties\&.
.sp
Note the format: double quotes, spaces and new lines are required\&. The
\fIstrategy\fR
specifies what to do if a controller specified already exists as a built\-in one:
\fBcriu\fR
can either
\fBmerge\fR
or
\fBreplace\fR
such\&.
.sp
For example, the command line for the above example should look like this:
.sp
.if n \{\
.RS 4
.\}
.fam C
.ps -1
.nf
.BB lightgray
\-\-cgroup\-props "\e"c1\e":\en \- \e"strategy\e": \e"merge\e"\en \- \e"properties\e": [\e"a\e", \e"b\e"]\en \e"c2\e":\en \- \e"strategy\e": \e"replace\e"\en \- \e"properties\e": [\e"c\e", \e"d\e"]"
.EB lightgray
.fi
.fam
.ps +1
.if n \{\
.RE
.\}
.RE
.PP
\fB\-\-cgroup\-props\-file\fR \fIfile\fR
.RS 4
Same as
\fB\-\-cgroup\-props\fR, except the specification is read from the
\fIfile\fR\&.
.RE
.PP
\fB\-\-cgroup\-dump\-controller\fR \fIname\fR
.RS 4
Dump a controller with
\fIname\fR
only, skipping anything else that was discovered automatically (usually via
\fB/proc\fR)\&. This option is useful when one needs
\fBcriu\fR
to skip some controllers\&.
.RE
.PP
\fB\-\-cgroup\-props\-ignore\-default\fR
.RS 4
When combined with
\fB\-\-cgroup\-props\fR, makes
\fBcriu\fR
substitute a predefined controller property with the new one shipped\&. If the option is not used, the predefined properties are merged with the provided ones\&.
.RE
.PP
\fB\-\-tcp\-established\fR
.RS 4
Checkpoint established TCP connections\&.
.RE
.PP
\fB\-\-skip\-in\-flight\fR
.RS 4
This option skips in\-flight TCP connections\&. If any TCP connections that are not yet completely established are found,
\fBcriu\fR
ignores these connections, rather than errors out\&. The TCP stack on the client side is expected to handle the re\-connect gracefully\&.
.RE
.PP
\fB\-\-tcp\-close\fR
.RS 4
Restore connected TCP sockets in closed state\&.
.RE
.PP
\fB\-\-evasive\-devices\fR
.RS 4
Use any path to a device file if the original one is inaccessible\&.
.RE
.PP
\fB\-\-page\-server\fR
.RS 4
Send pages to a page server (see the
\fBpage\-server\fR
command)\&.
.RE
.PP
\fB\-\-force\-irmap\fR
.RS 4
Force resolving names for inotify and fsnotify watches\&.
.RE
.PP
\fB\-\-auto\-dedup\fR
.RS 4
Deduplicate "old" data in pages images of previous
\fBdump\fR\&. This option implies incremental
\fBdump\fR
mode (see the
\fBpre\-dump\fR
command)\&.
.RE
.PP
\fB\-l\fR, \fB\-\-file\-locks\fR
.RS 4
Dump file locks\&. It is necessary to make sure that all file lock users are taken into dump, so it is only safe to use this for enclosed containers where locks are not held by any processes outside of dumped process tree\&.
.RE
.PP
\fB\-\-link\-remap\fR
.RS 4
Allows to link unlinked files back, if possible (modifies filesystem during
\fBrestore\fR)\&.
.RE
.PP
\fB\-\-ghost\-limit\fR \fIsize\fR
.RS 4
Set the maximum size of deleted file to be carried inside image\&. By default, up to 1M file is allowed\&. Using this option allows to not put big deleted files inside images\&. Argument
\fIsize\fR
may be postfixed with a
\fBK\fR,
\fBM\fR
or
\fBG\fR, which stands for kilo\-, mega, and gigabytes, accordingly\&.
.RE
.PP
\fB\-j\fR, \fB\-\-shell\-job\fR
.RS 4
Allow one to dump shell jobs\&. This implies the restored task will inherit session and process group ID from the
\fBcriu\fR
itself\&. This option also allows to migrate a single external tty connection, to migrate applications like
\fBtop\fR\&. If used with
\fBdump\fR
command, it must be specified with
\fBrestore\fR
as well\&.
.RE
.PP
\fB\-\-cpu\-cap\fR [\fIcap\fR[,\fIcap\fR\&...]]
.RS 4
Specify CPU capabilities to write to an image file\&. The argument is a comma\-separated list of
\fBnone\fR,
\fBfpu\fR,
\fBcpu\fR,
\fBins\fR,
\fBall\fR\&. If the argument is omitted or set to
\fBnone\fR, capabilities will not be written, which is the default behavior\&.
.RE
.PP
\fB\-\-cgroup\-root\fR [\fIcontroller\fR:]/\fInewroot\fR
.RS 4
Change the root for the controller that will be dumped\&. By default,
\fBcriu\fR
simply dumps everything below where any of the tasks live\&. However, if a container moves all of its tasks into a cgroup directory below the container engine\(cqs default directory for tasks, permissions will not be preserved on the upper directories with no tasks in them, which may cause problems\&.
.RE
.PP
\fB\-\-lazy\-pages\fR
.RS 4
Perform the dump procedure without writing memory pages into the image files and prepare to service page requests over the network\&. When
\fBdump\fR
runs in this mode it presumes that
\fBlazy\-pages\fR
daemon will connect to it and fetch memory pages to lazily inject them into the restored process address space\&. This option is intended for post\-copy (lazy) migration and should be used in conjunction with
\fBrestore\fR
with appropriate options\&.
.RE
.SS "restore"
.sp
Restores previously checkpointed processes\&.
.PP
\fB\-\-inherit\-fd\fR \fBfd[\fR\fIN\fR\fB]:\fR\fIresource\fR
.RS 4
Inherit a file descriptor\&. This option lets
\fBcriu\fR
use an already opened file descriptor
\fIN\fR
for restoring a file identified by
\fIresource\fR\&. This option can be used to restore an external resource dumped with the help of
\fB\-\-external\fR
\fBfile\fR,
\fBtty\fR, and
\fBunix\fR
options\&.
.sp
The
\fIresource\fR
argument can be one of the following:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fBtty[\fR\fIrdev\fR\fB:\fR\fIdev\fR\fB]\fR
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fBpipe[\fR\fIinode\fR\fB]\fR
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fBsocket[\fR\fIinode\fR\fB]\fR
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fBfile[\fR\fImnt_id\fR\fB:\fR\fIinode\fR\fB]\fR
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fIpath/to/file\fR
.RE
.sp
Note that square brackets used in this option arguments are literals and usually need to be escaped from shell\&.
.RE
.PP
\fB\-d\fR, \fB\-\-restore\-detached\fR
.RS 4
Detach
\fBcriu\fR
itself once restore is complete\&.
.RE
.PP
\fB\-s\fR, \fB\-\-leave\-stopped\fR
.RS 4
Leave tasks in stopped state after restore (rather than resuming their execution)\&.
.RE
.PP
\fB\-S\fR, \fB\-\-restore\-sibling\fR
.RS 4
Restore root task as a sibling (makes sense only with
\fB\-\-restore\-detached\fR)\&.
.RE
.PP
\fB\-r\fR, \fB\-\-root\fR \fIpath\fR
.RS 4
Change the root filesystem to
\fIpath\fR
(when run in a mount namespace)\&.
.RE
.PP
\fB\-\-external\fR \fItype\fR\fB[\fR\fIid\fR\fB]:\fR\fIvalue\fR
.RS 4
Restore an instance of an external resource\&. The generic syntax is
\fItype\fR
of resource, followed by resource
\fIid\fR
(enclosed in literal square brackets), and optional
\fIvalue\fR
(prepended by a literal semicolon)\&. The following resource types are currently supported:
\fBmnt\fR,
\fBdev\fR,
\fBveth\fR,
\fBmacvlan\fR\&. Syntax depends on type\&. Note to restore external resources dealing with opened file descriptors (such as dumped with the help of
\fB\-\-external\fR
\fBfile\fR,
\fBtty\fR, and
\fBunix\fR
options), option
\fB\-\-inherit\-fd\fR
should be used\&.
.RE
.PP
\fB\-\-external mnt[\fR\fIname\fR\fB]:\fR\fImountpoint\fR
.RS 4
Restore an external bind mount referenced in the image by
\fIname\fR, bind\-mounting it from the host
\fImountpoint\fR
to a proper mount point\&.
.RE
.PP
\fB\-\-external mnt[]\fR
.RS 4
Restore all external bind mounts (dumped with the help of
\fB\-\-external mnt[]\fR
auto\-detection)\&.
.RE
.PP
\fB\-\-external dev[\fR\fIname\fR\fB]:\fR\fI/dev/path\fR
.RS 4
Restore an external mount device, identified in the image by
\fIname\fR, using the existing block device
\fI/dev/path\fR\&.
.RE
.PP
\fB\-\-external veth[\fR\fIinner_dev\fR\fB]:\fR\fIouter_dev\fR\fB@\fR\fIbridge\fR
.RS 4
Set the outer VETH device name (corresponding to
\fIinner_dev\fR
being restored) to
\fIouter_dev\fR\&. If optional
\fB@\fR\fIbridge\fR
is specified,
\fIouter_dev\fR
is added to that bridge\&. If the option is not used,
\fIouter_dev\fR
will be autogenerated by the kernel\&.
.RE
.PP
\fB\-\-external macvlan[\fR\fIinner_dev\fR\fB]:\fR\fIouter_dev\fR
.RS 4
When restoring an image that have a MacVLAN device in it, this option must be used to specify to which
\fIouter_dev\fR
(an existing network device in CRIU namespace) the restored
\fIinner_dev\fR
should be bound to\&.
.RE
.PP
\fB\-\-manage\-cgroups\fR [\fImode\fR]
.RS 4
Restore cgroups configuration associated with a task from the image\&. Controllers are always restored in an optimistic way \(em if already present in system,
\fBcriu\fR
reuses it, otherwise it will be created\&.
.RE
.sp
The \fImode\fR may be one of the following:
.PP
\fBnone\fR
.RS 4
Do not restore cgroup properties but require cgroup to pre\-exist at the moment of
\fBrestore\fR
procedure\&.
.RE
.PP
\fBprops\fR
.RS 4
Restore cgroup properties and require cgroup to pre\-exist\&.
.RE
.PP
\fBsoft\fR
.RS 4
Restore cgroup properties if only cgroup has been created by
\fBcriu\fR, otherwise do not restore properties\&. This is the default if mode is unspecified\&.
.RE
.PP
\fBfull\fR
.RS 4
Always restore all cgroups and their properties\&.
.RE
.PP
\fBstrict\fR
.RS 4
Restore all cgroups and their properties from the scratch, requiring them to not present in the system\&.
.PP
\fB\-\-cgroup\-root\fR [\fIcontroller\fR\fB:\fR]/\fInewroot\fR
.RS 4
Change the root cgroup the controller will be installed into\&. No controller means that root is the default for all controllers not specified\&.
.RE
.PP
\fB\-\-tcp\-established\fR
.RS 4
Restore previously dumped established TCP connections\&. This implies that the network has been locked between
\fBdump\fR
and
\fBrestore\fR
phases so other side of a connection simply notice a kind of lag\&.
.RE
.PP
\fB\-\-veth\-pair\fR \fIIN\fR\fB=\fR\fIOUT\fR
.RS 4
Correspondence between outside and inside names of veth devices\&.
.RE
.PP
\fB\-l\fR, \fB\-\-file\-locks\fR
.RS 4
Restore file locks from the image\&.
.RE
.PP
\fB\-\-auto\-dedup\fR
.RS 4
As soon as a page is restored it get punched out from image\&.
.RE
.PP
\fB\-j\fR, \fB\-\-shell\-job\fR
.RS 4
Restore shell jobs, in other words inherit session and process group ID from the criu itself\&.
.RE
.PP
\fB\-\-cpu\-cap\fR [\fIcap\fR[,\fIcap\fR\&...]]
.RS 4
Specify CPU capabilities to be present on the CPU the process is restoring\&. To inverse a capability, prefix it with
\fB^\fR\&. This option implies that
\fB\-\-cpu\-cap\fR
has been passed on
\fBdump\fR
as well, except
\fBfpu\fR
option case\&. The
\fIcap\fR
argument can be the following (or a set of comma\-separated values):
.RE
.RE
.PP
\fBall\fR
.RS 4
Require all capabilities\&. This is
\fBdefault\fR
mode if
\fB\-\-cpu\-cap\fR
is passed without arguments\&. Most safe mode\&.
.RE
.PP
\fBcpu\fR
.RS 4
Require the CPU to have all capabilities in image to match runtime CPU\&.
.RE
.PP
\fBfpu\fR
.RS 4
Require the CPU to have compatible FPU\&. For example the process might be dumped with xsave capability but attempted to restore without it present on target CPU\&. In such case we refuse to proceed\&. This is
\fBdefault\fR
mode if
\fB\-\-cpu\-cap\fR
is not present in command line\&. Note this argument might be passed even if on the
\fBdump\fR
no
\fB\-\-cpu\-cap\fR
have been specified because FPU frames are always encoded into images\&.
.RE
.PP
\fBins\fR
.RS 4
Require CPU compatibility on instructions level\&.
.RE
.PP
\fBnone\fR
.RS 4
Ignore capabilities\&. Most dangerous mode\&. The behaviour is implementation dependent\&. Try to not use it until really required\&.
.sp
For example, this option can be used in case
\fB\-\-cpu\-cap=cpu\fR
was used during
\fBdump\fR, and images are migrated to a less capable CPU and are to be restored\&. By default,
\fBcriu\fR
shows an error that CPU capabilities are not adequate, but this can be suppressed by using
\fB\-\-cpu\-cap=none\fR\&.
.PP
\fB\-\-weak\-sysctls\fR
.RS 4
Silently skip restoring sysctls that are not available\&. This allows to restore on an older kernel, or a kernel configured without some options\&.
.RE
.PP
\fB\-\-lazy\-pages\fR
.RS 4
Restore the processes without filling out the entire memory contents\&. When this option is used,
\fBrestore\fR
sets up the infrastructure required to fill memory pages either on demand when the process accesses them or in the background without stopping the restored process\&. This option requires running
\fBlazy\-pages\fR
daemon\&.
.RE
.RE
.SS "check"
.sp
Checks whether the kernel supports the features needed by \fBcriu\fR to dump and restore a process tree\&.
.sp
There are three categories of kernel support, as described below\&. \fBcriu check\fR always checks Category 1 features unless \fB\-\-feature\fR is specified which only checks a specified feature\&.
.PP
\fBCategory 1\fR
.RS 4
Absolutely required\&. These are features like support for
\fB/proc/PID/map_files\fR,
\fBNETLINK_SOCK_DIAG\fR
socket monitoring,
\fB/proc/sys/kernel/ns_last_pid\fR
etc\&.
.RE
.PP
\fBCategory 2\fR
.RS 4
Required only for specific cases\&. These are features like AIO remap,
\fB/dev/net/tun\fR
and others that are only required if a process being dumped or restored is using those\&.
.RE
.PP
\fBCategory 3\fR
.RS 4
Experimental\&. These are features like
\fBtask\-diag\fR
that are used for experimental purposes (mostly during development)\&.
.RE
.sp
If there are no errors or warnings, \fBcriu\fR prints "Looks good\&." and its exit code is 0\&.
.sp
A missing Category 1 feature causes \fBcriu\fR to print "Does not look good\&." and its exit code is non\-zero\&.
.sp
Missing Category 2 and 3 features cause \fBcriu\fR to print "Looks good but \&..." and its exit code is be non\-zero\&.
.sp
Without any options, \fBcriu check\fR checks Category 1 features\&. This behavior can be changed by using the following options:
.PP
\fB\-\-extra\fR
.RS 4
Check kernel support for Category 2 features\&.
.RE
.PP
\fB\-\-experimental\fR
.RS 4
Check kernel support for Category 3 features\&.
.RE
.PP
\fB\-\-all\fR
.RS 4
Check kernel support for Category 1, 2, and 3 features\&.
.RE
.PP
\fB\-\-feature\fR \fIname\fR
.RS 4
Check a specific feature\&. If
\fIname\fR
is
\fBlist\fR, a list of valid kernel feature names that can be checked will be printed\&.
.RE
.SS "page\-server"
.sp
Launches \fBcriu\fR in page server mode\&.
.PP
\fB\-\-daemon\fR
.RS 4
Runs page server as a daemon (background process)\&.
.RE
.PP
\fB\-\-status_fd\fR
.RS 4
Write \e\e0 to the FD and close it once page\-server is ready to handle requests\&. The status\-fd allows to not daemonize a process and get its exit code at the end\&. It isn\(cqt supposed to use \-\-daemon and \-\-status\-fd together\&.
.RE
.PP
\fB\-\-address\fR \fIaddress\fR
.RS 4
Page server IP address\&.
.RE
.PP
\fB\-\-port\fR \fInumber\fR
.RS 4
Page server port number\&.
.RE
.PP
\fB\-\-lazy\-pages\fR
.RS 4
Serve local memory dump to a remote
\fBlazy\-pages\fR
daemon\&. In this mode the
\fBpage\-server\fR
reads local memory dump and allows the remote
\fBlazy\-pages\fR
deamon to request memory pages in random order\&.
.RE
.SS "lazy\-pages"
.sp
Launches \fBcriu\fR in lazy\-pages daemon mode\&.
.sp
The \fBlazy\-pages\fR daemon is responsible for managing user\-level demand paging for the restored processes\&. It gets information required to fill the process memory pages from the \fBrestore\fR and from the checkpont directory\&. When a restored process access certain memory page for the first time, the \fBlazy\-pages\fR daemon injects its contents into the process address space\&. The memory pages that are not yet requested by the restored processes are injected in the background\&.
.SS "exec"
.sp
Executes a system call inside a destination task\*(Aqs context\&. This functionality is deprecated; please use \fBCompel\fR instead\&.
.SS "service"
.sp
Launches \fBcriu\fR in RPC daemon mode, where \fBcriu\fR is listening for RPC commands over socket to perform\&. This is convenient for a case where daemon itself is running in a privileged (superuser) mode but clients are not\&.
.SS "dedup"
.sp
Starts pagemap data deduplication procedure, where \fBcriu\fR scans over all pagemap files and tries to minimize the number of pagemap entries by obtaining the references from a parent pagemap image\&.
.SS "cpuinfo dump"
.sp
Fetches current CPU features and write them into an image file\&.
.SS "cpuinfo check"
.sp
Fetches current CPU features (i\&.e\&. CPU the \fBcriu\fR is running on) and test if they are compatible with the ones present in an image file\&.
.SH "EXAMPLES"
.sp
To checkpoint a program with pid of \fB1234\fR and write all image files into directory \fBcheckpoint\fR:
.sp
.if n \{\
.RS 4
.\}
.fam C
.ps -1
.nf
.BB lightgray
    criu dump \-D checkpoint \-t 1234
.EB lightgray
.fi
.fam
.ps +1
.if n \{\
.RE
.\}
.sp
To restore this program detaching criu itself:
.sp
.if n \{\
.RS 4
.\}
.fam C
.ps -1
.nf
.BB lightgray
    criu restore \-d \-D checkpoint
.EB lightgray
.fi
.fam
.ps +1
.if n \{\
.RE
.\}
.SH "AUTHOR"
.sp
The CRIU team\&.
.SH "COPYRIGHT"
.sp
Copyright (C) 2011\-2016, Parallels Holdings, Inc\&.