CRIT

This page describes the CRIT Python tool. For the Go library, see CRIT (Go library).

CRiu Image Tool is a feature-rich replacement for existing "criu show". It is written completely in Python, so it is quite easy to read the code and extend its features.

Usage

usage: crit [-h] {decode,encode,info,x,show} ...

CRiu Image Tool

positional arguments:
  {decode,encode,info,x,show}
                        Use crit CMD --help for command-specific help
    decode              convert criu image from binary type to json
    encode              convert criu image from json type to binary
    info                show info about image
    x                   explore image dir
    show                convert criu image from binary to human-readable json

optional arguments:
  -h, --help            show this help message and exit

Pretty output

crit decode prints JSON text in one line. This can be read by any further JSON-aware tool for parsing. For human eyes it's more convenient to read JSON multi-line with indentation. CRIT can do this when using the show action or the --pretty option.

Wend doing pretty optput CRIT does a little bit more, than just multiline indented JSON.

Addresses and registers

VM addresses and core.img register values are all printed in hex. Since JSON doesn't support this form of numbers, such fields are encoded as strings.

Bit-fields

Such things as flags and masks (e.g. sig-block mask) are also better understood when written in hex, so CRIT does this.

IP addresses

By default those a printed in decimal, but the "1.2.3.4" for v4 or "::1" for v6 can be seen in the --pretty mode.

Symbolic names for flags

Some known bit sets (e.g. MAP_PRIVATE, MAP_ANONYMOUS, etc. for vma->flags) are shown with names.

Device numbers

If the field is known to be of dev_t type, it's printed in the major:minor manner

Functionality

Convert images from IMG to JSON

crit decode is the replacement for the (rather nasty) criu show code. This is also the way to edit the images before restoring from them.

It uses text_format as a human-readable format for protobuf messages.

The output file is structured in the following way.

Without "--pretty":

{ "magic" : "FOO", "entries" : [{"foo": "bar", "bar": "foo", "extra": "abc"}, {"foo": "bar", "bar" : "foo", "extra" : "abc"} ]}

With "--pretty":

{
    "magic" : "FOO",
    "entries" : [
        {
            "foo" : "bar",
            "bar" : "foo",
            "extra" : "abc"
        },
        {
            "foo" : "bar",
            "bar" : "foo",
            "extra" : "abc"
        }
    ]
}

Example("crit decode -i core-5679.img --pretty")

{
    "magic": "CORE", 
    "entries": [
        {
            "mtype": "X86_64", 
            "thread_core": {
                "futex_rla_len": 24, 
                "sched_policy": 0, 
                "sched_nice": 0, 
                "futex_rla": 0, 
                "signals_p": {}, 
                "sas": {
                    "ss_size": 0, 
                    "ss_sp": 0, 
                    "ss_flags": 2
                }
            }, 
            "thread_info": {
                "fpregs": {
                    "st_space": [
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0
                    ], 
                    "fop": 0, 
                    "rdp": 0, 
                    "twd": 0, 
                    "mxcsr": 8064, 
                    "swd": 0, 
                    "rip": 0, 
                    "xsave": {
                        "ymmh_space": [
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0, 
                            0
                        ], 
                        "xstate_bv": 2
                    }, 
                    "xmm_space": [
                        0, 
                        4278190080, 
                        4294967295, 
                        4294967295, 
                        1701145715, 
                        3219568, 
                        0, 
                        0, 
                        0, 
                        0, 
                        33, 
                        0, 
                        792358505, 
                        1953460082, 
                        1852400175, 
                        0, 
                        942882145, 
                        876295483, 
                        774519349, 
                        1031303283, 
                        893073459, 
                        976565307, 
                        1937255978, 
                        859661936, 
                        993344312, 
                        3814708, 
                        65, 
                        0, 
                        37049520, 
                        0, 
                        37049632, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        4294901760, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0, 
                        0
                    ], 
                    "cwd": 0, 
                    "mxcsr_mask": 65535
                }, 
                "clear_tid_addr": 0, 
                "gpregs": {
                    "gs": "0x0", 
                    "ip": "0x7f172cf1ea04", 
                    "cx": "0xffffffffffffffff", 
                    "cs": "0x33", 
                    "ax": "0x38", 
                    "orig_ax": "0x38", 
                    "di": "0x1200011", 
                    "es": "0x0", 
                    "gs_base": "0x0", 
                    "r14": "0x0", 
                    "r15": "0x2355e00", 
                    "r12": "0x7ffffdbf74f0", 
                    "r13": "0x0", 
                    "r10": "0x7f172d83d9d0", 
                    "r11": "0x246", 
                    "fs_base": "0x7f172d83d700", 
                    "bp": "0x7ffffdbf7530", 
                    "dx": "0x0", 
                    "bx": "0x0", 
                    "ds": "0x0", 
                    "ss": "0x2b", 
                    "sp": "0x7ffffdbf74f0", 
                    "r8": "0x0", 
                    "r9": "0x0", 
                    "fs": "0x0", 
                    "si": "0x0", 
                    "flags": "0x246"
                }
            }, 
            "tc": {
                "timers": {
                    "real": {
                        "isec": 0, 
                        "vusec": 0, 
                        "iusec": 0, 
                        "vsec": 0
                    }, 
                    "virt": {
                        "isec": 0, 
                        "vusec": 0, 
                        "iusec": 0, 
                        "vsec": 0
                    }, 
                    "prof": {
                        "isec": 0, 
                        "vusec": 0, 
                        "iusec": 0, 
                        "vsec": 0
                    }
                }, 
                "cg_set": 1, 
                "signals_s": {}, 
                "blk_sigset": "0x10002", 
                "exit_code": 0, 
                "rlimits": {
                    "rlimits": [
                        {
                            "max": 18446744073709551615, 
                            "cur": 18446744073709551615
                        }, 
                        {
                            "max": 18446744073709551615, 
                            "cur": 18446744073709551615
                        }, 
                        {
                            "max": 18446744073709551615, 
                            "cur": 18446744073709551615
                        }, 
                        {
                            "max": 18446744073709551615, 
                            "cur": 8388608
                        }, 
                        {
                            "max": 18446744073709551615, 
                            "cur": 0
                        }, 
                        {
                            "max": 18446744073709551615, 
                            "cur": 18446744073709551615
                        }, 
                        {
                            "max": 62844, 
                            "cur": 62844
                        }, 
                        {
                            "max": 4096, 
                            "cur": 1024
                        }, 
                        {
                            "max": 65536, 
                            "cur": 65536
                        }, 
                        {
                            "max": 18446744073709551615, 
                            "cur": 18446744073709551615
                        }, 
                        {
                            "max": 18446744073709551615, 
                            "cur": 18446744073709551615
                        }, 
                        {
                            "max": 62844, 
                            "cur": 62844
                        }, 
                        {
                            "max": 819200, 
                            "cur": 819200
                        }, 
                        {
                            "max": 0, 
                            "cur": 0
                        }, 
                        {
                            "max": 0, 
                            "cur": 0
                        }, 
                        {
                            "max": 18446744073709551615, 
                            "cur": 18446744073709551615
                        }
                    ]
                }, 
                "comm": "loop.sh", 
                "flags": 1077960704, 
                "task_state": 1, 
                "personality": 0
            }
        }
    ]
}

Decode also supports input via STDIN instead of the "-i" flag.

cat "core-5679.img" | crit decode 

Convert images from JSON to IMG

crit encode converts the image from JSON to IMG. Standard usage would look like:

crit encode -i core-5679.json -o core-5679.img

Encode also supports input via STDIN instead of the "-i" flag.

cat "core-5679.json" | crit encode 

Incase a "-o" flag is not specified the input is piped out to STDOUT.

Generate core files out of task images

Moved into separate project called criu-coredump.

Show images statistics

crit x allows you to explore image statistics. E.g. Total number of processes, files, memory, sockets, etc.

crit x $directory_with_images <explore type>

Supported explorers are

'ps'

to show process tree

'fds'

to show files used by tasks

'mems'

to show memory mappings info

Show images Info

Image of a info such as its "COUNT" and "MAGIC" can be displayed using the INFO command.

Example("crit info core-5679.img")

{
    "count": 1, 
    "magic": "CORE"
}

Planned functionality

On-the-fly conversion

There's an idea to make CRIU spawn CRIT and read images "through" it, to allow for at-the-restore-time modifications. For details, see https://github.com/checkpoint-restore/criu/issues/59.

Convert between different image versions

Right now we store the images version in inventory.img and collect info about what's bad with V1 images. If some day we have v2, CRIT will convert from v1. And for backward compatibility we'll use on-the-fly conversion when restoring from old images.

Check/validate images

Check that

• all images are present
• the inter-images IDs are in consistent state

For details, see https://github.com/checkpoint-restore/criu/issues/44.

Anonymize image files

Since images contain raw memory dumps people may refuse to send us images for debugging. Need to anonymize them, i.e. -- remove this sensitive information.