I have a multi container application with multiple containers based on the same base image. When I inspect the image sizes on a device, the application images take a considerable amount of storage space. Is there a way to deploy the application so the base image layer is shared between application images, in order to reduce download sizes?
Hi there! Could you provide some info on the steps you 've been using for verifying the RX bandwidth actually used? Also, how are you checking the image sizes?
Images using the same base layer, include its size on the total image size reported per image (via balena images for example), however, the base image should be downloaded and saved just once.
I have not checked the actual used bandwidth, but would be happy to be able to.
I checked the image sizes looking into the balenaCloud release tab. What I also did was ssh into the device and:
root@f14c40f:~# balena-engine images
REPOSITORY TAG IMAGE ID CREATED SIZE
registry2.balena-cloud.com/v2/da791489804e3628b36cfefbe4657c4a <none> 675475b4ea43 20 hours ago 115MB
registry2.balena-cloud.com/v2/7ce9d187833ad1a3b41607000743121d <none> 2d99eb6d7129 21 hours ago 87.5MB
registry2.balena-cloud.com/v2/365219cd1d0ffb5f293b6cabe0f47556 <none> 509de069ec1a 22 hours ago 86.7MB
registry2.balena-cloud.com/v2/6283c51a4f530de9973a95e4e8ad0f10 <none> 3b372cb651c7 2 days ago 54.5MB
registry2.balena-cloud.com/v2/c0797faf2840116ac797065a51d101ad <none> f562bf3857f9 2 days ago 54.5MB
registry2.balena-cloud.com/v2/db91f2af7ef5170e08a3aa2cd509d83f <none> 31edb96344b8 2 days ago 139MB
balena/amd64-supervisor v10.2.2 326aafd36af4 3 months ago 49.5MB
hello-world latest fce289e99eb9 11 months ago 1.84kB
Is it possible to inspect the actual layers that are persisted on the device and display their sizes?
Tnx
Bruno
Hi Bruno
command balena history <IMAGE ID> will provide the list of layers as well as their sizes
Cheers
federico
Hi Federico,
I get something like this:
root@f14c40f:~# balena-engine history 2d99eb6d7129
IMAGE CREATED CREATED BY SIZE COMMENT
2d99eb6d7129 2 days ago /bin/sh -c #(nop) CMD ["python3" "./compres… 0B
<missing> 2 days ago /bin/sh -c #(nop) COPY file:86d30a247e873244… 2.02kB
<missing> 2 days ago /bin/sh -c install_packages lame python3 && … 52MB
<missing> 2 days ago /bin/sh -c #(nop) COPY file:23cd687ba511edbd… 194kB
<missing> 12 days ago /bin/sh -c curl -SLO "https://raw.githubuser… 0B
<missing> 12 days ago /bin/sh -c #(nop) ENTRYPOINT ["/usr/bin/ent… 0B
<missing> 12 days ago /bin/sh -c #(nop) COPY file:182ce03eab3864ad… 1.54kB
<missing> 12 days ago /bin/sh -c #(nop) ENV UDEV=off 0B
<missing> 12 days ago /bin/sh -c curl -SLO "http://resin-packages.… 1.62MB
<missing> 12 days ago /bin/sh -c apk add --no-cache bash ca-ce… 28.1MB
<missing> 12 days ago /bin/sh -c #(nop) LABEL io.balena.architect… 0B
<missing> 6 weeks ago /bin/sh -c #(nop) CMD ["/bin/sh"] 0B
<missing> 6 weeks ago /bin/sh -c #(nop) ADD file:fe1f09249227e2da2… 5.55MB
What does the label tell me? I thought each layer on my device had its own id.
Tnx
Bruno
Hey Bruno
yes, it makes sense: if you sum the values in the SIZE column you’ll get a number close to that 87.5MB that images reported
cheers
federico
For the record, another way to look at what makes an image is docker inspect <IMAGEID>. It will print a json document with a RootFS key that will list the images overlays
cheers
federico
I did that for two of my application images, getting the following results in the json:
"RootFS": {
"Type": "layers",
"Layers": [
"sha256:77cae8ab23bf486355d1b3191259705374f4a11d483b24964d2f729dd8c076a0",
"sha256:26db6b77ba50af49be09d25309019e65006551cee1107da1e5efc5405e7a319e",
"sha256:e6b43765c5b2a633d408bed35d0dbeb01e38494cd582bc43c85116db73c5a8ba",
"sha256:4427b4542a0005e5b4c782305ea1b4be56c075318ca62da995ec69c7ddf95017",
"sha256:0da85665fcd32b7cf094d2202eebe2023cbf264dc02905b4397c9e845b823473",
"sha256:986c357479ad0a187aab4b82c7f16d0f09ec23e1218490c9498bd1fa10a2829d"
]
}
and
"RootFS": {
"Type": "layers",
"Layers": [
"sha256:77cae8ab23bf486355d1b3191259705374f4a11d483b24964d2f729dd8c076a0",
"sha256:26db6b77ba50af49be09d25309019e65006551cee1107da1e5efc5405e7a319e",
"sha256:e6b43765c5b2a633d408bed35d0dbeb01e38494cd582bc43c85116db73c5a8ba",
"sha256:4427b4542a0005e5b4c782305ea1b4be56c075318ca62da995ec69c7ddf95017",
"sha256:05f8712f3a0a90c04ad75a3c2511f5ce95ecb87b1f2cabd6dd8910566a3f3e0c",
"sha256:b4b73ea68a488ad208d73161d1910c48dd44a9a960914e012ae36d1f70620f4b",
"sha256:68a8a09189c1862d554bc75af796215c89acaba7bbc11ca5b5e027af577d081f"
]
}
Is my understanding correct?
- The first 4 layers are used by both images.
- The other layers are different
- The first 4 layers are stored only once in my devices filesystem, although their size contributes to both total image sizes displayed in the balenaCloud releases tab.
Thanks
Bruno
Hi there,
This is absolutely correct, the first 4 layers will only appear once in the filing system and will be shared by both of the images.
You’re also correct in the assertion that the image size shown for both images is the total for all layers. balenaEngine (and Docker), only request the layers that are not already present on a device when an application update occurs, thus minimising the amount of data transferred. However, there are even more savings to be had, and we also offer Delta updates for images as well (see here for more information on deltas).
Best regards,
Heds
Hello Balena team. Great support again, chapeau.
Bruno
You’re most welcome! Please let us know if you have any other questions in the future!
Best regards,
Heds