mirror of
https://github.com/linuxkit/linuxkit.git
synced 2025-10-31 05:12:03 +00:00
9a1d9fb1eb
Since I struggled to understand and find information about how to troubleshoot a running linuxkit instance, I propose to add these two FAQ entries. The first one explains why it is possible to not see the `containerd` or `init` outputs at boot in the console. The second one gives a few `ctr` example to list containers, running containers or how to open a shell in a given container. Signed-off-by: Brice Figureau <brice@daysofwonder.com>
79 lines
3.1 KiB
Markdown
79 lines
3.1 KiB
Markdown
# FAQ
|
|
|
|
Please open an issue if you want to add a question here.
|
|
|
|
## How do updates work?
|
|
|
|
LinuxKit does not require being installed on a disk, it is often run from an ISO, PXE or other
|
|
such means, so it does not require an on disk upgrade method such as the ChromeOS code that
|
|
is often used. It would definitely be possible to use that type of upgrade method if the
|
|
system is installed, and it would be useful to support this for that use case, and an
|
|
updater container to control this for people who want to use this.
|
|
|
|
We generally use external tooling such as [Infrakit](https://github.com/docker/infrakit) or
|
|
CloudFormation templates to manage the update process externally from LinuxKit, including
|
|
doing rolling cluster upgrades to make sure distributed applications stay up and responsive.
|
|
|
|
Updates may preserve the state disk used by applications if needed, either on the same physical
|
|
node, or by reattaching a virtual cloud volume to a new node.
|
|
|
|
## What do I need to build LinuxKit?
|
|
|
|
We have tried to make this as simple as possible, by using containers for the build process, so
|
|
you should be able to build LinuxKit on any OSX or Linux laptop; we should have Windows build support
|
|
soon.
|
|
|
|
## Why not use `systemd`?
|
|
|
|
In order to keep the system minimal, `systemd` did not seem appropriate, as it brings in a lot
|
|
of dependencies and functionality that we do not need. At present we are using the `busybox`
|
|
`init` process, and a small set of minimal scripts, but we expect to replace that with a small
|
|
standalone `init` process and a small piece of code to bring up the system containers where the
|
|
real work takes place.
|
|
|
|
## Console not displaying init or containerd output at boot
|
|
|
|
If you're not seeing `containerd` logs in the console during boot, make sure that your kernel `cmdline` configuration doesn't list multiple consoles.
|
|
|
|
`init` and other processes like `containerd` will use the last defined console in the kernel `cmdline`. When using `qemu`, to see the console you need to list `ttyS0` as the last console to properly see the output.
|
|
|
|
## Troubleshooting containers
|
|
|
|
Linuxkit runs all services in a specific `containerd` namespace called `services.linuxkit`. To list all the defined containers:
|
|
|
|
```sh
|
|
(ns: getty) linuxkit-befde23bc535:~# ctr -n services.linuxkit container ls
|
|
CONTAINER IMAGE RUNTIME
|
|
getty - io.containerd.runtime.v1.linux
|
|
```
|
|
|
|
To list all running containers and their status:
|
|
|
|
```sh
|
|
(ns: getty) linuxkit-befde23bc535:~# ctr -n services.linuxkit task ls
|
|
TASK PID STATUS
|
|
getty 661 RUNNING
|
|
```
|
|
|
|
To list all processes running in a container:
|
|
|
|
```sh
|
|
(ns: getty) linuxkit-befde23bc535:/containers/services/getty# ctr -n services.linuxkit task ps getty
|
|
PID INFO
|
|
661 &ProcessDetails{ExecID:getty,}
|
|
677 -
|
|
685 -
|
|
686 -
|
|
687 -
|
|
1237 -
|
|
```
|
|
|
|
To attach a shell to a running container:
|
|
|
|
```sh
|
|
(ns: getty) linuxkit-befde23bc535:/containers/services/getty# ctr -n services.linuxkit tasks exec --tty --exec-id sh sshd /bin/ash -l
|
|
(ns: sshd) linuxkit-befde23bc535:/#
|
|
```
|
|
|
|
Containers are defined as OCI bundles in `/containers`.
|