AutoFS

2016-04-22T15:07:05Z

Skinsbursky:

AutoFS

2016-04-22T14:59:16Z

Skinsbursky:

2012-07-27T08:13:32Z

Skinsbursky:

{{Download box}}
Welcome to CRIU, a project to implement checkpoint/restore functionality for Linux in userspace.

== Releases ==

* [http://download.openvz.org/criu/crtools-0.1.tar.bz2 crtools-0.1.tar.bz2] 23 Jul 2012 (sha1 aa1a9af42f4132e00701555a00ee3884cbe0c36b)

== Using ==

;[[CR_tools | CR tools]]
: Main checkpoint/restore utility description (sort of HOWTO)

;[[Usage scenarios]]
: Ideas how crtools can be used (some are crazy indeed)

;[[What software is supported]]
: Describes TODO list in higher level terms

== Developing ==

If you're interested in CRIU development, subscribe to the criu mailing list: https://openvz.org/mailman/listinfo/criu

;[[Images]]
: Description of image files format

;[[Commits | Commits]]
: Mainline kernel commits tracker

;[[ZDTM_Test_Suite | ZDTM]]
: Zero downtime test suite

;[[Todo | TODO]]
: Current TODO list

== External links ==
{{:Articles}}

== Under the hood ==

Articles about how things are done in crtools

* [[Sockets]]
* [[Memory dumping and restoring]]
* [[Checkpoint/Restore]]
* [[TCP connection]]
* [[Porting crtools to new kernel releases]]
* [[Files]]

2012-01-19T12:45:28Z

Skinsbursky:

{| class="wikitable sortable"
|-
! component
! task
! assignee
! status
! comments
|-
| kernel || children entry in procfs || gorcunov@ || sent-for-review || -
|-
| crtools || Sockets dump/restore || xemul@/gorcunov@ || partially implemented || [[Sockets]]
|-
| kernel/crtools || socket queues dump || xemul@ || in progress || prototype exists, need to send
|-
| crtools || UDP sockets support || Adrian Reber || in progress? || need to utilize the udp diag subsys
|-
| kernel/crtools || TCP sockets support || xemul@ || - || have no idea :(
|-
| crtools || Unix in-flight connections support || gorcunov@ || - || need to use the ICONS diag field
|-
| kernel || kernel object IDs || gorcunov@ || sent-for-review || -
|-
| crtools || Fix memory checkpointing || - || not implemented || [[Memory dumping and restoring]]
|-
| kernel/crtools || Fix mincore bits || xemul@ || sent-for-review || -
|-
| kernel/crtools || Rework and submit MINCORE_ANON || xemul@ || sent-for-review || -
|-
| kernel/crtools || Implement MINCORE_SWAP - swapped pages are skipped by us currently || xemul@ || sent-for-review || -
|-
| kernel/crtools || Fix shared regions migration || gorcunov@ || - || -
|-
| crtools || Learn to work with shared struct file-s || avagin@ || done || depends on "object IDs". Need to send file via unix socket
|-
| kernel/crtools || Learn to work with namespaces (ipc and net are of the most interest) || gorcunov@ || not implemented || depends on "object IDs"
|-
| crtools || Shared objects (mm/fs/fdtable) support || avagin@ || not implemented || depends on "object IDs"
|-
| kernel || Provide own defconfig || gorcunov@ || not implemented || suggested by avagin@
|-
| crtools || Get rid of shmem_update_real_pid() || gorcunov@ || - || this one was required when we restored tasks without pids. Nowadays this can be removed.
|-
| crtools || Dump restoration logs to per-pid log file || avagin@/gorcunov@ || - || Otherwise there's a mess with on-screen flood
|-
| crtools || Task IDs -- gid/suid/sid/fsid/etc. || gorcunov@ || - || -
|-
| crtools || Task's ignored signals mask || gorcunov@ || - || -
|-
| crtools || Rework dump_one_reg_file to use fhandles || - || - || This is required to work with overmounted files and not to store the long file path (will not work with rsync-ed private :( )
|-
| crtools || terminals || - || - || -
|-
| crtools || Add make check so tests are automated || - || - || -
|-
| crtools || IPC || - || - || -
|-
| crtools || Drop redundant getpid() calls || gorcunov@ || - || It seems there are a few places where we do call getpid() which we know already
|-
| crtools || man-page || gorcunov@ || - || -
|-
| crtools || fix broken comm (after restore) || gorcunov@ || - || This requires to extend prctl for restore and add output for args in /proc
|-
| crtools || fix broken exe (after restore) || gorcunov@ || - ||
|-
| crtools || add separate type for futex-s || avagin@ || - ||
|}

2012-01-12T10:51:00Z

Skinsbursky: /* Configure the linux kernel */

== What CRtools is ==

'''CRtools''' is an utility to checkpoint/restore process tree. Unlike checkpoint/restore implemented completely in kernel space,
it tries to achieve the same target operating in user space. Since the tools and overall concept are still under heavy development
stage there are some known limitations applied

# Only pure x86-64 environment is supported, no IA32 emulation allowed.
# There is no way to use cgroups freezer facility yet.
# No network or IPC checkpoint/restore supported.

== Basic design ==

=== Checkpoint ===

The checkpoint procedure relies heavily on '''/proc''' file system (it's a general place where crtools takes all the information it needs).
Which includes

* Files descriptors information (via '''/proc/$pid/fd''' and '''/proc/$pid/fdinfo''').
* Pipes parameters.
* Memory maps (via '''/proc/$pid/maps''').

The process dumper (lets call it a dumper further) does the following steps during checkpoint stage

# A '''$pid''' of a process group leader is obtained from the command line.
# By using this '''$pid''' the dumper walks though '''/proc/$pid/status''' and gathers children '''$pids''' recursively. At the end we will have a process tree.
# Then it takes every '''$pid''' from a process tree, sends ''SIGSTOP'' to every process found, and performs the following steps on each '''$pid'''.
#* Collects VMA areas by parsing '''/proc/$pid/maps'''.
#* Seizes a task via relatively new ptrace interface. Seizing a task means to put it into a special state when the task have no idea if it's being operated by ptrace.
#* Core parameters of a task (such as registers and friends) are being dumped via ptrace interface and parsing '''/proc/$pid/stat''' entry.
#* The dumper injects a parasite code into a task via ptrace interface. This allows us to dump pages of a task right from within the task's address space.
#** An injection procedure is pretty simple - the dumper scans executable VMA areas of a task (which were collected previously) and tests if there a place for <code>syscall</code> call, then (by ptrace as well) it substitutes an original code with <code>syscall</code> instructions and creates a new VMA area inside process address space.
#** Finally parasite code get copied into the new VMA and the former code which was modified during parasite bootstrap procedure get restored.
#* Then (by using a parasite code) the dumper flushes contents of a task's pages to the file. And pulls out parasite code block completely, since we don't need it anymore.
#* Once parasite removed a task get unseized via ptrace call but it remains stopped still.
#* The dumper writes out files and pipes parameter and data.
# The procedure continues for every '''$pid'''.

=== Restore ===

The restore procedure (aka restorer) proceed in the following steps

# A process tree has been read from a file.
# Every process started with saved (i.e. original) '''$pid''' via <code>clone()</code> call.
# Files and pipes are restored (by restored it's meant - they are opened and positioned).
# A new memory map is created, filled with data the program had at checkpoint time.
# Finally the program is kicked to start with rt_sigreturn system call.



== Download crtools ==

The '''crtools''' utility itself is hosted at [https://github.com/cyrillos/crtools github].
Clone this repo to test new functionality.

Also '''crtools''' requires some additional patches to be applied on the linux kernel (on top of v3.2-rc6 to be precise).

So clone [https://github.com/cyrillos/linux-2.6 linux-2.6-crtools.git], checkout ''crtools'' branch
and compile the kernel.

== Configure the linux kernel ==

Make sure you have the following options turned on

# General setup -> Checkpoint/restore support (CONFIG_CHECKPOINT_RESTORE)
# Networking support -> Networking options -> Unix domain sockets -> UNIX: socket monitoring interface (CONFIG_UNIX_DIAG)
# Processor type and features -> Enable generic object ID infrastructure (CONFIG_GENERIC_OBJECT_ID)

Note you might have to enable

* General setup -> Configure standard kernel features (expert users) (CONFIG_EXPERT)

option, which depends on

* General setup -> Embedded system (CONFIG_EMBEDDED)

(welcome to Kconfig reverse chains hell).