sha256:a9561eb1b190625c9adb5a9513e72c4dedafc1cb2d4c5236c9a6957ec7dfd5a9.
Layers must be packed and unpacked reproducibly to avoid changing the
layer ID, for example by using tar-split to save the tar headers. Note
that the digest used as the layer ID is taken over an uncompressed
version of the tar.
ChainID. For a
single layer (or the layer at the bottom of a stack), the
ChainID is equal to the layer's DiffID.
Otherwise the ChainID is given by the formula:
ChainID(layerN) = SHA256hex(ChainID(layerN-1) + " " + DiffID(layerN)).
sha256:a9561eb1b190625c9adb5a9513e72c4dedafc1cb2d4c5236c9a6957ec7dfd5a9.
Since the configuration JSON that gets hashed references hashes of each
layer in the image, this formulation of the ImageID makes images
content-addressable.
[a-zA-Z0-9_.-], except they may not start with a .
or - character. Tags are limited to 128 characters.
:). For example, in an image tagged with the name
my-app:3.1.4, my-app is the Repository
component of the name. A repository name is made up of slash-separated
name components, optionally prefixed by a DNS hostname. The hostname
must comply with standard DNS rules, but may not contain
_ characters. If a hostname is present, it may optionally
be followed by a port number in the format :8080.
Name components may contain lowercase characters, digits, and
separators. A separator is defined as a period, one or two underscores,
or one or more dashes. A name component may not start or end with
a separator.
string
string
string
string
struct
null, in
which case any execution parameters should be specified at creation of
the container.
string
The username or UID which the process in the container should run as. This acts as a default value to use when the value is not specified when creating a container.
All of the following are valid:
useruiduser:groupuid:giduid:groupuser:gidIf group/gid is not specified, the
default group and supplementary groups of the given
user/uid in /etc/passwd
from the container are applied.
integer
integer
-1 to
disable swap. This acts as a default value to use when the
value is not specified when creating a container.
integer
struct
map[string]struct{} and is represented in JSON as
an object mapping its keys to an empty object. Here is an
example:
{
"8080": {},
"53/udp": {},
"2356/tcp": {}
}
Its keys can be in the format of:
"port/tcp"
"port/udp"
"port"
"tcp" if not
specified. These values act as defaults and are merged with
any specified when creating a container.
array of strings
VARNAME="var value".
These values act as defaults and are merged with any specified
when creating a container.
array of strings
array of strings
Entrypoint value is
not specified, then the first entry of the Cmd
array should be interpreted as the executable to run.
boolean
Entrypoint
or Cmd or both, contain only a single element array
that is a pre-escaped, and combined into a single string, **CommandLine**.
If "true", the value in Entrypoint or CmdCmd
should be used as-is to avoid double escaping.
Note, the exact behavior of ArgsEscaped is complex
and subject to implementation details.
struct
{
"Test": [
"CMD-SHELL",
"/usr/bin/check-health localhost"
],
"Interval": 30000000000,
"Timeout": 10000000000,
"Retries": 3,
"StartInterval": 3000000000
}
The object has the following fields.
array of strings
[] : inherit healthcheck from base image["NONE"] : disable healthcheck["CMD", arg1, arg2, ...] : exec arguments directly["CMD-SHELL", command] : run command with system's default shellinteger
integer
integer
integer
struct
map[string]struct{} and is represented in
JSON as an object mapping its keys to an empty object. Here is
an example:
{
"/var/my-app-data/": {},
"/etc/some-config.d/": {},
}
string
array of strings
array of strings
["/bin/sh", "-c"], and ["cmd", "/S", "/C"]
on Windows. This field is set by the SHELL
instruction in a Dockerfile, and *must* be written in JSON
form.
struct
type is usually set to layers.
diff_ids is an array of layer content hashes (DiffIDs), in order from bottom-most to top-most.
"rootfs": {
"diff_ids": [
"sha256:c6f988f4874bb0add23a778f753c65efe992244e148a1d2ec2a8b664fb66bbd1",
"sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef",
"sha256:13f53e08df5a220ab6d13c58b2bf83a59cbdc2e04d0a3f041ddf4b0ba4112d49"
],
"type": "layers"
}
struct
history is an array of objects describing the history of
each layer. The array is ordered from bottom-most layer to top-most
layer. The object has the following fields.
created: Creation time, expressed as a ISO-8601 formatted
combined date and time
author: The author of the build point
created_by: The command which created the layer
comment: A custom message set when creating the layer
empty_layer: This field is used to mark if the history
item created a filesystem diff. It is set to true if this history
item doesn't correspond to an actual layer in the rootfs section
(for example, a command like ENV which results in no change to the
filesystem).
"history": [
{
"created": "2015-10-31T22:22:54.690851953Z",
"created_by": "/bin/sh -c #(nop) ADD file:a3bc1e842b69636f9df5256c49c5374fb4eef1e281fe3f282c65fb853ee171c5 in /"
},
{
"created": "2015-10-31T22:22:55.613815829Z",
"created_by": "/bin/sh -c #(nop) CMD [\"sh\"]",
"empty_layer": true
}
]