| title | weight | description |
|---|---|---|
Using top file |
20 |
Periodically report read/write activity by file.
|
The top file gadget is used to visualize reads and writes by file, with container details.
This guide will deploy an example workload that performs some disk I/O
activity to show how to use top file.
Before starting our workload, let's start our top file gadget to be sure it captures all the events from the beginning:
$ kubectl gadget top file -p mypod
NODE NAMESPACE POD CONTAINER PID COMM READS WRITES R_Kb W_Kb T FILE
...The T column indicates the type of the file: R for regular files, S for
sockets, and O for other (including pipes). By default only regular files are
shown; use the -a option to show all file types.
In another terminal, let's create our pod. It'll install git and then
clone the linux source code.
$ kubectl run -it mypod --image ubuntu -- /bin/sh -c "apt-get update && apt-get install -y git && git clone https://github.com/torvalds/linux"
We can see how the top file terminal shows the files that are read and
written by the pod. For instace, apt-get is reading a lot of files in
when updating the packages list and installing packages.
NODE NAMESPACE POD CONTAINER PID COMM READS WRITES R_Kb W_Kb T FILE
ubuntu-hirsute default mypod mypod 642727 apt-get 425 0 27022 0 R archive.ubuntu.com_ubuntu_dists_focal-updates_main_binary-amd64_Packages.lz4
ubuntu-hirsute default mypod mypod 642727 apt-get 278 0 17775 0 R archive.ubuntu.com_ubuntu_dists_focal_main_binary-amd64_Packages.lz4
ubuntu-hirsute default mypod mypod 642727 apt-get 244 0 15594 0 R security.ubuntu.com_ubuntu_dists_focal-security_main_binary-amd64_Packages.lz4
ubuntu-hirsute default mypod mypod 642727 apt-get 93 0 5921 0 R archive.ubuntu.com_ubuntu_dists_focal_universe_binary-amd64_Packages.lz4
ubuntu-hirsute default mypod mypod 642727 apt-get 91 0 5797 0 R archive.ubuntu.com_ubuntu_dists_focal-updates_universe_binary-amd64_Packages.lz4
ubuntu-hirsute default mypod mypod 642727 apt-get 82 0 5160 0 R archive.ubuntu.com_ubuntu_dists_focal-updates_restricted_binary-amd64_Packages.lz4
ubuntu-hirsute default mypod mypod 642727 apt-get 73 0 4568 0 R security.ubuntu.com_ubuntu_dists_focal-security_restricted_binary-amd64_Packages.lz4
ubuntu-hirsute default mypod mypod 642727 apt-get 70 0 4435 0 R security.ubuntu.com_ubuntu_dists_focal-security_universe_binary-amd64_Packages.lz4
ubuntu-hirsute default mypod mypod 642727 apt-get 19 0 1172 0 R archive.ubuntu.com_ubuntu_dists_focal_multiverse_binary-amd64_Packages.lz4After the initial installation is done, we can see how git uses a temporary file to store the repository being cloned.
NODE NAMESPACE POD CONTAINER PID COMM READS WRITES R_Kb W_Kb T FILE
ubuntu-hirsute default mypod mypod 647042 git 0 1070 0 4280 R tmp_pack_2rpZd
Finally, we need to clean up our pod, press Ctrl + C on its terminal and them remove it:
$ kubectl delete pod mypodBy default the top file gadget prints a summary each second. It accepts a numeric argument to indicate the interval to use:
$ kubectl gadget top file 5 # will print a summary each 5 secondsThis gadget also supports the following flags to customize the output:
$ kubectl gadget top file --help
Trace reads and writes by file
Usage:
kubectl-gadget top file [interval] [flags]
Flags:
-a, --all-files Include non-regular file types (sockets, FIFOs, etc)
...
-r, --maxrows int Maximum rows to print (default 20)
...Start a container that performs some write operations to a file:
$ docker run --rm --name test-top-file busybox /bin/sh -c 'while true; do echo foo > bar; sleep 1; done'Start the gadget and it'll show those operations:
$ sudo ig top file -c test-top-file
CONTAINER PID COMM READS WRITES RBYTES WBYTES T FILE
test-top-file 139255 sh 0 1 0B 4B R bar