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[edit]
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[edit]
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_ttype, it's printed in themajor:minormanner
Functionality[edit]
Convert images from IMG to JSON[edit]
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[edit]
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[edit]
Moved into separate project called criu-coredump.
Show images statistics[edit]
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[edit]
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[edit]
On-the-fly conversion[edit]
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[edit]
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[edit]
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[edit]
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.