CRIU(8) CRIU Manual CRIU(8)
NAME criu - checkpoint/restore in userspace
SYNOPSIS
criu command [option ...]
DESCRIPTION
criu is a tool for checkpointing and restoring running applications. It
does this by saving their state as a collection of files (see the dump
command) and creating equivalent processes from those files (see the re-
store command). The restore operation can be performed at a later time,
on a different system, or both.
OPTIONS
Most of the long flags can be prefixed with no- to negate the option
(example: --display-stats and --no-display-stats).
Common options
Common options are applicable to any command.
-v[v...], --verbosity
Increase verbosity up from the default level. In case of short op-
tion, multiple v can be used, each increasing verbosity by one.
-vnum, --verbosity=num
Set verbosity level to num. The higher the level, the more output is
produced.
The following levels are available:
• -v0 no output;
• -v1 only errors;
• -v2 above plus warnings (this is the default level);
• -v3 above plus information messages and timestamps;
• -v4 above plus lots of debug.
--config file
Pass a specific configuration file to criu.
--no-default-config
Disable parsing of default configuration files.
--pidfile file
Write root task, service or page-server pid into a file.
-o, --log-file file
Write logging messages to a file.
--display-stats
During dump, as well as during restore, criu collects some statis-
tics, like the time required to dump or restore the process, or the
number of pages dumped or restored. This information is always saved
to the stats-dump and stats-restore files, and can be shown using
crit(1). The option --display-stats prints out this information on
the console at the end of a dump or restore operation.
-D, --images-dir path
Use path as a base directory where to look for sets of image files.
--stream
dump/restore images using criu-image-streamer. See
https://github.com/checkpoint-restore/criu-image-streamer for de-
tailed usage.
--prev-images-dir path
Use path as a parent directory where to look for sets of image
files. This option makes sense in case of incremental dumps.
-W, --work-dir dir
Use directory dir for putting logs, pidfiles and statistics. If not
specified, path from -D option is taken.
--close fd
Close file descriptor fd before performing any actions.
-L, --libdir path
Path to plugins directory.
--enable-fs [fs[,fs...]]
Specify a comma-separated list of filesystem names that should be
auto-detected. The value all enables auto-detection for all filesys-
tems.
Note: This option is not safe, use at your own risk. Auto-detecting
a filesystem mount assumes that the mountpoint can be restored with
mount(src, mountpoint, flags, options). When used, dump is expected
to always succeed if a mountpoint is to be auto-detected, however
restore may fail (or do something wrong) if the assumption for re-
store logic is incorrect. This option is not compatible with --ex-
ternal dev.
--action-script script
Add an external action script to be executed at certain stages. The
environment variable CRTOOLS_SCRIPT_ACTION is available to the
script to find out which action is being executed, and its value can
be one of the following:
pre-dump
run prior to beginning a dump
post-dump
run upon dump completion
pre-restore
run prior to beginning a restore
post-restore
run upon restore completion
pre-resume
run when all processes and resources are restored but tasks are
stopped waiting for final kick to run. Must not fail.
post-resume
called at the very end, when everything is restored and
processes were resumed
network-lock
run to lock network in a target network namespace
network-unlock
run to unlock network in a target network namespace
setup-namespaces
run once root task has just been created with required name-
spaces. Note it is an early stage of restore, when nothing is
restored yet, except for namespaces themselves
post-setup-namespaces
called after the namespaces are configured
orphan-pts-master
called after master pty is opened and unlocked. This hook can be
used only in the RPC mode, and the notification message contains
a file descriptor for the master pty
query-ext-files
called after the process tree is stopped and network is locked.
This hook is used only in the RPC mode. The notification reply
contains file ids to be added to external file list (may be
empty).
--unprivileged
This option tells criu to accept the limitations when running as
non-root. Running as non-root requires criu at least to have
CAP_SYS_ADMIN or CAP_CHECKPOINT_RESTORE. For details about running
criu as non-root please consult the NON-ROOT section.
-V, --version
Print program version and exit.
-h, --help
Print some help and exit.
pre-dump
Performs the pre-dump procedure, during which criu creates a snapshot of
memory changes since the previous pre-dump. Note that during this criu
also creates the fsnotify cache which speeds up the restore procedure.
pre-dump requires at least -t option (see dump below). In addition,
page-server options may be specified.
--track-mem
Turn on memory changes tracker in the kernel. If the option is not
passed the memory tracker get turned on implicitly.
--pre-dump-mode=mode
There are two mode to operate pre-dump algorithm. The splice mode is
parasite based, whereas read mode is based on process_vm_readv
syscall. The read mode incurs reduced frozen time and reduced memory
pressure as compared to splice mode. Default is splice mode.
dump
Performs a checkpoint procedure.
-t, --tree pid
Checkpoint the whole process tree starting from pid.
-R, --leave-running
Leave tasks in running state after checkpoint, instead of killing.
This option is pretty dangerous and should be used only if you un-
derstand what you are doing.
Note if task is about to run after been checkpointed, it can modify
TCP connections, delete files and do other dangerous actions. There-
fore, criu can not guarantee that the next restore action will suc-
ceed. Most likely if this option is used, at least the file system
snapshot must be made with the help of post-dump action script.
In other words, do not use it unless really needed.
-s, --leave-stopped
Leave tasks in stopped state after checkpoint, instead of killing.
--external type[id]:value
Dump an instance of an external resource. The generic syntax is type
of resource, followed by resource id (enclosed in literal square
brackets), and optional value (prepended by a literal colon). The
following resource types are currently supported: mnt, dev, file,
tty, unix. Syntax depends on type. Note to restore external re-
sources, either --external or --inherit-fd is used, depending on re-
source type.
--external mnt[mountpoint]:name
Dump an external bind mount referenced by mountpoint, saving it to
image under the identifier name.
--external mnt[]:flags
Dump all external bind mounts, autodetecting those. Optional flags
can contain m to also dump external master mounts, s to also dump
external shared mounts (default behavior is to abort dumping if such
mounts are found). If flags are not provided, colon is optional.
--external dev[major/minor]:name
Allow to dump a mount namespace having a real block device mounted.
A block device is identified by its major and minor numbers, and
criu saves its information to image under the identifier name.
--external file[mnt_id:inode]
Dump an external file, i.e. an opened file that is can not be re-
solved from the current mount namespace, which can not be dumped
without using this option. The file is identified by mnt_id (a field
obtained from /proc/pid/fdinfo/N) and inode (as returned by
stat(2)).
--external tty[rdev:dev]
Dump an external TTY, identified by st_rdev and st_dev fields re-
turned by stat(2).
--external unix[id]
Tell criu that one end of a pair of UNIX sockets (created by socket-
pair(2)) with the given id is OK to be disconnected.
--external net[inode]:name
Mark a network namespace as external and do not include it in the
checkpoint. The label name can be used with --inherit-fd during re-
store to specify a file descriptor to a preconfigured network name-
space.
--external pid[inode]:name
Mark a PID namespace as external. This can be later used to restore
a process into an existing PID namespace. The label name can be used
to assign another PID namespace during restore with the help of
--inherit-fd.
--freeze-cgroup
Use cgroup freezer to collect processes.
--manage-cgroups
Collect cgroups into the image thus they gonna be restored then.
Without this option, criu will not save cgroups configuration asso-
ciated with a task.
--cgroup-props spec
Specify controllers and their properties to be saved into the image
file. criu predefines specifications for common controllers, but
since the kernel can add new controllers and modify their proper-
ties, there should be a way to specify ones matched the kernel.
spec argument describes the controller and properties specification
in a simplified YAML form:
"c1":
- "strategy": "merge"
- "properties": ["a", "b"]
"c2":
- "strategy": "replace"
- "properties": ["c", "d"]
where c1 and c2 are controllers names, and a, b, c, d are their
properties.
Note the format: double quotes, spaces and new lines are required.
The strategy specifies what to do if a controller specified already
exists as a built-in one: criu can either merge or replace such.
For example, the command line for the above example should look like
this:
--cgroup-props "\"c1\":\n - \"strategy\": \"merge\"\n - \"properties\": [\"a\", \"b\"]\n \"c2\":\n - \"strategy\": \"replace\"\n - \"properties\": [\"c\", \"d\"]"
--cgroup-props-file file
Same as --cgroup-props, except the specification is read from the
file.
--cgroup-dump-controller name
Dump a controller with name only, skipping anything else that was
discovered automatically (usually via /proc). This option is useful
when one needs criu to skip some controllers.
--cgroup-yard path
Instead of trying to mount cgroups in CRIU, provide a path to a di-
rectory with already created cgroup yard. Useful if you don’t want
to grant CAP_SYS_ADMIN to CRIU. For every cgroup mount there should
be exactly one directory. If there is only one controller in this
mount, the dir’s name should be just the name of the controller. If
there are multiple controllers comounted, the directory name should
have them be separated by a comma.
For example, if /proc/cgroups looks like this:
#subsys_name hierarchy num_cgroups enabled
cpu 1 1 1
devices 2 2 1
freezer 2 2 1
then you can create the cgroup yard by the following commands:
mkdir private_yard
cd private_yard
mkdir cpu
mount -t cgroup -o cpu none cpu
mkdir devices,freezer
mount -t cgroup -o devices,freezer none devices,freezer
--tcp-established
Checkpoint established TCP connections.
--tcp-close
Don’t dump the state of, or block, established tcp connections (in-
cluding the connection is once established but now closed). This is
useful when tcp connections are not going to be restored.
--skip-in-flight
This option skips in-flight TCP connections. If any TCP connections
that are not yet completely established are found, criu ignores
these connections, rather than errors out. The TCP stack on the
client side is expected to handle the re-connect gracefully.
--evasive-devices
Use any path to a device file if the original one is inaccessible.
--page-server
Send pages to a page server (see the page-server command).
--force-irmap
Force resolving names for inotify and fsnotify watches.
--auto-dedup
Deduplicate "old" data in pages images of previous dump. This option
implies incremental dump mode (see the pre-dump command).
-l, --file-locks
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 en-
closed containers where locks are not held by any processes outside
of dumped process tree.
--link-remap
Allows to link unlinked files back, if possible (modifies filesystem
during restore).
--timeout number
Set a time limit in seconds for collecting tasks during the dump op-
eration. The timeout is 10 seconds by default.
--ghost-limit size
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 size may be postfixed
with a K, M or G, which stands for kilo-, mega, and gigabytes, ac-
cordingly.
--ghost-fiemap
Enable an optimization based on fiemap ioctl that can reduce the
number of system calls used when checkpointing highly sparse ghost
files. This option is enabled by default, and it can be disabled
with --no-ghost-fiemap. An automatic fallback to SEEK_HOLE/SEEK_DATA
is used when fiemap is not supported.
-j, --shell-job
Allow one to dump shell jobs. This implies the restored task will
inherit session and process group ID from the criu itself. This op-
tion also allows to migrate a single external tty connection, to mi-
grate applications like top. If used with dump command, it must be
specified with restore as well.
--cpu-cap [cap[,cap...]]
Specify CPU capabilities to write to an image file. The argument is
a comma-separated list of:
• none to ignore capabilities at all; the image will not be pro-
duced on dump, neither any check performed on restore;
• fpu to check if FPU module is compatible;
• ins to check if CPU supports all instructions required;
• cpu to check if CPU capabilities are exactly matching;
• all for all above set.
By default the option is set to fpu and ins.
--cgroup-root [controller:]/newroot
Change the root for the controller that will be dumped. By default,
criu simply dumps everything below where any of the tasks live. How-
ever, if a container moves all of its tasks into a cgroup directory
below the container engine’s default directory for tasks, permis-
sions will not be preserved on the upper directories with no tasks
in them, which may cause problems.
--lazy-pages
Perform the dump procedure without writing memory pages into the im-
age files and prepare to service page requests over the network.
When dump runs in this mode it presumes that lazy-pages 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
restore with appropriate options.
--file-validation [mode]
Set the method to be used to validate open files. Validation is done
to ensure that the version of the file being restored is the same
version when it was dumped.
The mode may be one of the following:
filesize
To explicitly use only the file size check all the time. This is
the fastest and least intensive check.
buildid
To validate ELF files with their build-ID. If the build-ID can-
not be obtained, chksm-first method will be used. This is the
default if mode is unspecified.
--network-lock [mode]
Set the method to be used for network locking/unlocking. Locking is
done to ensure that tcp packets are dropped between dump and re-
store. This is done to avoid the kernel sending RST when a packet
arrives destined for the dumped process.
The mode may be one of the following:
iptables
Use iptables rules to drop the packets. This is the default if
mode is not specified.
nftables
Use nftables rules to drop the packets.
skip
Don’t lock the network. If --tcp-close is not used, the network
must be locked externally to allow CRIU to dump TCP connections.
restore
Restores previously checkpointed processes.
--inherit-fd fd[N]:resource
Inherit a file descriptor. This option lets criu use an already
opened file descriptor N for restoring a file identified by re-
source. This option can be used to restore an external resource
dumped with the help of --external file, tty, pid and unix options.
The resource argument can be one of the following:
• tty[rdev:dev]
• pipe[inode]
• socket[inode*]*
• file[mnt_id:inode]
• path/to/file
Note that square brackets used in this option arguments are literals
and usually need to be escaped from shell.
-d, --restore-detached
Detach criu itself once restore is complete.
-s, --leave-stopped
Leave tasks in stopped state after restore (rather than resuming
their execution).
-S, --restore-sibling
Restore root task as a sibling (makes sense only with --restore-de-
tached).
--log-pid
Write separate logging files per each pid.
-r, --root path
Change the root filesystem to path (when run in a mount namespace).
This option is required to restore a mount namespace. The directory
path must be a mount point and its parent must not be overmounted.
--external type[id]:value
Restore an instance of an external resource. The generic syntax is
type of resource, followed by resource id (enclosed in literal
square brackets), and optional value (prepended by a literal colon).
The following resource types are currently supported: mnt, dev,
veth, macvlan. Syntax depends on type. Note to restore external re-
sources dealing with opened file descriptors (such as dumped with
the help of --external file, tty, and unix options), option --in-
herit-fd should be used.
--external mnt[name]:mountpoint
Restore an external bind mount referenced in the image by name,
bind-mounting it from the host mountpoint to a proper mount point.
--external mnt[]
Restore all external bind mounts (dumped with the help of --external
mnt[] auto-detection).
--external dev[name]:/dev/path
Restore an external mount device, identified in the image by name,
using the existing block device /dev/path.
--external veth[inner_dev]:outer_dev@bridge
Set the outer VETH device name (corresponding to inner_dev being re-
stored) to outer_dev. If optional @bridge is specified, outer_dev is
added to that bridge. If the option is not used, outer_dev will be
autogenerated by the kernel.
--external macvlan[inner_dev]:outer_dev
When restoring an image that have a MacVLAN device in it, this op-
tion must be used to specify to which outer_dev (an existing network
device in CRIU namespace) the restored inner_dev should be bound to.
-J, --join-ns NS:{PID|NS_FILE}[,EXTRA_OPTS]
Restore process tree inside an existing namespace. The namespace can
be specified in PID or NS_FILE path format (example: --join-ns
net:12345 or --join-ns net:/foo/bar). Currently supported values for
NS are: ipc, net, time, user, and uts. This option doesn’t support
joining a PID namespace, however, this is possible using --external
and --inheritfd. EXTRA_OPTS is optional and can be used to specify
UID and GID for user namespace (e.g., --join-ns user:PID,UID,GID).
--manage-cgroups [mode]
Restore cgroups configuration associated with a task from the image.
Controllers are always restored in an optimistic way — if already
present in system, criu reuses it, otherwise it will be created.
The mode may be one of the following:
none
Do not restore cgroup properties but require cgroup to pre-exist
at the moment of restore procedure.
props
Restore cgroup properties and require cgroup to pre-exist.
soft
Restore cgroup properties if only cgroup has been created by
criu, otherwise do not restore properties. This is the default
if mode is unspecified.
full
Always restore all cgroups and their properties.
strict
Restore all cgroups and their properties from the scratch, re-
quiring them to not present in the system.
ignore
Don’t deal with cgroups and pretend that they don’t exist.
--cgroup-yard path
Instead of trying to mount cgroups in CRIU, provide a path to a di-
rectory with already created cgroup yard. For more information look
in the dump section.
--cgroup-root [controller:]/newroot
Change the root cgroup the controller will be installed into. No
controller means that root is the default for all controllers not
specified.
--tcp-established
Restore previously dumped established TCP connections. This implies
that the network has been locked between dump and restore phases so
other side of a connection simply notice a kind of lag.
--tcp-close
Restore connected TCP sockets in closed state.
--veth-pair IN=OUT
Correspondence between outside and inside names of veth devices.
-l, --file-locks
Restore file locks from the image.
--lsm-profile type:name
Specify an LSM profile to be used during restore. The type can be
either apparmor or selinux.
--lsm-mount-context context
Specify a new mount context to be used during restore.
This option will only replace existing mount context information
with the one specified with this option. Mounts without the context=
option will not be changed.
If a mountpoint has been checkpointed with an option like
context="system_u:object_r:container_file_t:s0:c82,c137"
it is possible to change this option using
--lsm-mount-context "system_u:object_r:container_file_t:s0:c204,c495"
which will result that the mountpoint will be restored with the new
context=.
This option is useful if using selinux and if the selinux labels
need to be changed on restore like if a container is restored into
an existing Pod.
--auto-dedup
As soon as a page is restored it get punched out from image.
-j, --shell-job
Restore shell jobs, in other words inherit session and process group
ID from the criu itself.
--cpu-cap [cap[,cap...]]
Specify CPU capabilities to be present on the CPU the process is
restoring. To inverse a capability, prefix it with ^. This option
implies that --cpu-cap has been passed on dump as well, except fpu
option case. The cap argument can be the following (or a set of
comma-separated values):
all
Require all capabilities. This is default mode if --cpu-cap is
passed without arguments. Most safe mode.
cpu
Require the CPU to have all capabilities in image to match run-
time CPU.
fpu
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 pro-
ceed. This is default mode if --cpu-cap is not present in com-
mand line. Note this argument might be passed even if on the
dump no --cpu-cap have been specified because FPU frames are al-
ways encoded into images.
ins
Require CPU compatibility on instructions level.
none
Ignore capabilities. Most dangerous mode. The behaviour is im-
plementation dependent. Try to not use it until really required.
For example, this option can be used in case --cpu-cap=cpu was
used during dump, and images are migrated to a less capable CPU
and are to be restored. By default, criu shows an error that CPU
capabilities are not adequate, but this can be suppressed by us-
ing --cpu-cap=none.
--weak-sysctls
Silently skip restoring sysctls that are not available. This allows
to restore on an older kernel, or a kernel configured without some
options.
--lazy-pages
Restore the processes without filling out the entire memory con-
tents. When this option is used, restore sets up the infrastructure
required to fill memory pages either on demand when the process ac-
cesses them or in the background without stopping the restored
process. This option requires running lazy-pages daemon.
--file-validation [mode]
Set the method to be used to validate open files. Validation is done
to ensure that the version of the file being restored is the same
version when it was dumped.
The mode may be one of the following:
filesize
To explicitly use only the file size check all the time. This is
the fastest and least intensive check.
buildid
To validate ELF files with their build-ID. If the build-ID can-
not be obtained, chksm-first method will be used. This is the
default if mode is unspecified.
--skip-file-rwx-check
Skip checking file permissions (r/w/x for u/g/o) on restore.
check
Checks whether the kernel supports the features needed by criu to dump
and restore a process tree.
There are three categories of kernel support, as described below. criu
check always checks Category 1 features unless --feature is specified
which only checks a specified feature.
Category 1
Absolutely required. These are features like support for
/proc/PID/map_files, NETLINK_SOCK_DIAG socket monitoring,
/proc/sys/kernel/ns_last_pid etc.
Category 2
Required only for specific cases. These are features like AIO remap,
/dev/net/tun and others that are only required if a process being
dumped or restored is using those.
Category 3
Experimental. These are features like task-diag that are used for
experimental purposes (mostly during development).
If there are no errors or warnings, criu prints "Looks good." and its
exit code is 0.
A missing Category 1 feature causes criu to print "Does not look good."
and its exit code is non-zero.
Missing Category 2 and 3 features cause criu to print "Looks good but
..." and its exit code is be non-zero.
Without any options, criu check checks Category 1 features. This behav-
ior can be changed by using the following options:
--extra
Check kernel support for Category 2 features.
--experimental
Check kernel support for Category 3 features.
--all
Check kernel support for Category 1, 2, and 3 features.
--feature name
Check a specific feature. If name is list, a list of valid kernel
feature names that can be checked will be printed.
page-server
Launches criu in page server mode.
--daemon
Runs page server as a daemon (background process).
--status-fd
Write \0 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’t supposed to use --daemon and
--status-fd together.
--address address
Page server IP address or hostname.
--port number
Page server port number.
--ps-socket fd
Use provided file descriptor as socket for incoming connection. In
this case --address and --port are ignored. Useful for intercepting
page-server traffic e.g. to add encryption or authentication.
--lazy-pages
Serve local memory dump to a remote lazy-pages daemon. In this mode
the page-server reads local memory dump and allows the remote
lazy-pages daemon to request memory pages in random order.
--tls-cacert file
Specifies the path to a trusted Certificate Authority (CA) certifi-
cate file to be used for verification of a client or server certifi-
cate. The file must be in PEM format. When this option is used only
the specified CA is used for verification. Otherwise, the system’s
trusted CAs and, if present, /etc/pki/CA/cacert.pem will be used.
--tls-cacrl file
Specifies a path to a Certificate Revocation List (CRL) file which
contains a list of revoked certificates that should no longer be
trusted. The file must be in PEM format. When this option is not
specified, the file, if present, /etc/pki/CA/cacrl.pem will be used.
--tls-cert file
Specifies a path to a file that contains a X.509 certificate to
present to the remote entity. The file must be in PEM format. When
this option is not specified, the default location
(/etc/pki/criu/cert.pem) will be used.
--tls-key file
Specifies a path to a file that contains TLS private key. The file
must be in PEM format. When this option is not the default location
(/etc/pki/criu/private/key.pem) will be used.
--tls
Use TLS to secure remote connections.
lazy-pages
Launches criu in lazy-pages daemon mode.
The lazy-pages daemon is responsible for managing user-level demand pag-
ing for the restored processes. It gets information required to fill the
process memory pages from the restore and from the checkpoint directory.
When a restored process access certain memory page for the first time,
the lazy-pages 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.
exec
Executes a system call inside a destination task's context. This func-
tionality is deprecated; please use Compel instead.
service
Launches criu in RPC daemon mode, where criu is listening for RPC com-
mands over socket to perform. This is convenient for a case where daemon
itself is running in a privileged (superuser) mode but clients are not.
dedup
Starts pagemap data deduplication procedure, where criu scans over all
pagemap files and tries to minimize the number of pagemap entries by ob-
taining the references from a parent pagemap image.
cpuinfo dump
Fetches current CPU features and write them into an image file.
cpuinfo check
Fetches current CPU features (i.e. CPU the criu is running on) and test
if they are compatible with the ones present in an image file.
CONFIGURATION FILES
Criu supports usage of configuration files to avoid the need of writing
every option on command line, which is useful especially with repeated
usage of same options. A specific configuration file can be passed with
the "--config file" option. If no file is passed, the default configura-
tion files /etc/criu/default.conf and $HOME/.criu/default.conf are
parsed (if present on the system). If the environment variable CRIU_CON-
FIG_FILE is set, it will also be parsed.
The options passed to CRIU via CLI, RPC or configuration file are evalu-
ated in the following order:
• apply_config(/etc/criu/default.conf)
• apply_config($HOME/.criu/default.conf)
• apply_config(CRIU_CONFIG_FILE)
• apply_config(--config file)
• apply_config(CLI) or apply_config(RPC)
• apply_config(RPC configuration file) (only for RPC mode)
Default configuration file parsing can be deactivated with "--no-de-
fault-config" if needed. Parsed configuration files are merged with com-
mand line options, which allows overriding boolean options.
Configuration file syntax
Comments are supported using '#' sign. The rest of the line is ignored.
Options are the same as command line options without the '--' prefix,
use one option per line (with corresponding argument if applicable, di-
vided by whitespaces). If needed, the argument can be provided in double
quotes (this should be needed only if the argument contains white-
spaces). In case this type of argument contains a literal double quote
as well, it can be escaped using the '\' sign. Usage of commands is dis-
allowed and all other escape sequences are interpreted literally.
Example of configuration file to illustrate syntax:
$ cat ~/.criu/default.conf
tcp-established
work-dir "/home/USERNAME/criu/my \"work\" directory"
#this is a comment
no-restore-sibling # this is another comment
Configuration files in RPC mode
Not only does criu evaluate configuration files in CLI mode, it also
evaluates configuration files in RPC mode. Just as in CLI mode the con-
figuration file values are evaluated first. This means that any option
set via RPC will overwrite the configuration file setting. The user can
thus change criu's default behavior but it is not possible to change
settings which are explicitly set by the RPC client.
The RPC client can, however, specify an additional configuration file
which will be evaluated after the RPC options (see above for option
evaluation order). The RPC client can specify this additional configura-
tion file via "req.opts.config_file = /path/to/file". The values from
this configuration file will overwrite all other configuration file set-
tings or RPC options. This can lead to undesired behavior of criu and
should only be used carefully.
NON-ROOT
criu can be used as non-root with either the CAP_SYS_ADMIN capability or
with the CAP_CHECKPOINT_RESTORE capability introduces in Linux kernel
5.9. CAP_CHECKPOINT_RESTORE is the minimum that is required.
criu also needs either CAP_SYS_PTRACE or a value of 0 in /proc/sys/ker-
nel/yama/ptrace_scope (see ptrace(2)) to be able to interrupt the
process for dumping.
Running criu as non-root has many limitations and depending on the
process to checkpoint and restore it may not be possible.
In addition to CAP_CHECKPOINT_RESTORE it is possible to give criu addi-
tional capabilities to enable additional features in non-root mode.
Currently criu can benefit from the following additional capabilities:
• CAP_NET_ADMIN
• CAP_SYS_CHROOT
• CAP_SETUID
• CAP_SYS_RESOURCE
Note that for some operations, having a capability in a namespace other
than the init namespace (i.e. the default/root namespace) is not suffi-
cient. For example, in order to read symlinks in proc/[pid]/map_files
CRIU requires CAP_CHECKPOINT_RESTORE in the init namespace; having
CAP_CHECKPOINT_RESTORE while running in another user namespace (e.g. in
a container) does not allow CRIU to read symlinks in
/proc/[pid]/map_files.
Without access to /proc/[pid]/map_files checkpointing/restoring
processes that have mapped deleted files may not be possible.
Independent of the capabilities it is always necessary to use "--unpriv-
ileged" to accept criu's limitation in non-root mode.
EXAMPLES
To checkpoint a program with pid of 1234 and write all image files into
directory checkpoint:
criu dump -D checkpoint -t 1234
To restore this program detaching criu itself:
criu restore -d -D checkpoint
AUTHOR
The CRIU team.
COPYRIGHT
Copyright (C) 2011-2016, Parallels Holdings, Inc.
criu 4.1.1 07/29/2025 CRIU(8)
Generated by dwww version 1.16 on Tue Dec 16 06:47:29 CET 2025.