For almost two years Mike Rapoport and I have been working on lazy
process migration. Lazy process migration (or post-copy migration) is a
technique to decrease the process or container downtime during the live
migration. I described the basic functionality in the following previous
articles:

Those articles are not 100% correct anymore as we changed some of the
parameters during the last two years, but the concepts stayed the same.

Mike and I started about two years ago to work on it and the latest
CRIU release
(3.5)
includes the possibility to
use lazy migration. Now that the post-copy migration feature has been
merged from the criu-dev branch to the master branch it is part of
the normal CRIU releases.

With CRIU’s 3.5 release lazy migration can be used on any kernel which
supports
userfaultfd.
I already updated the CRIU packages in Fedora to 3.5 so that lazy
process migration can be used just by installing the latest CRIU
packages with dnf (still in the testing repository right now).

More information about container live migration in our upcoming Open
Source Summit Europe talk: Container Migration Around The
World
.

My pull request to
support lazy migration in
runC was also recently
merged, so that it is now possible to migrate containers using pre-copy
migration and post-copy migration. It can also be combined.

Another interesting change about CRIU is that it started as x86_64
only and now it is also available on aarch64, ppc64le and s390x.
The support to run on s390x has just been added with the previous 3.4
release and starting with Fedora 27 the necessary kernel configuration
options are also active on s390x in addition to the other supported
architectures.

As I’m currently switching phones I had to revisit the issue of how to get sshd running on a pristine LineageOS install. I decided to collect the steps here as the how-to formerly available on the CM wiki has vanished together with CM itself. Note that some  steps are not incredibly detailed and you really should be aware of the security implications before going ahead with this.

Prerequisites

Configuring SSHD

While LineageOS includes all necessary software, the configuration of sshd must be completed manually:

  1. Connect the device via USB
  2. Run adb with root privileges:
    adb root
  3. Upload your public ssh key to the device:
    adb push ~/.ssh/id_rsa.pub /data/ssh/authorized_keys
  4. Now, open a root shell and switch to bash to get vim to behave nicely on the device through adb:
    adb shell
    bash
  5. Use cat or vim to make the following fragment the contents of /data/ssh/sshd_config:

    AuthorizedKeysFile /data/ssh/authorized_keys
    ChallengeResponseAuthentication no
    PasswordAuthentication no
    PermitRootLogin no
    Subsystem sftp internal-sftp
    pidfile /data/ssh/sshd.pid

  6. Place a modified version of the start script in the userinit.d directory:
    mkdir /data/local/userinit.d
    sed 's#/system/etc/ssh#/data/ssh#' /system/bin/start-ssh
          > /data/local/userinit.d/99sshd
  7. Now correct the file privileges:
    chmod 755 /data/local/userinit.d/99sshd
    chmod 600 /data/ssh/authorized_keys
    chown shell /data/ssh/authorized_keys
    chmod 644 /data/ssh/sshd_config

Running SSHD

Now you should be able to run sshd manually by executing
/data/local/userinit.d/99sshd
If so you can log on as user shell to the device using your ssh key. See my previous post to find out how you can make sure sshd is started whenever the device is booted.

It is a bit late but I still wanted to share my presentations from this
year’s Linux Plumbers Conference:

On my way back home I had to stay one night in Albuquerque and it looks
like the hotel needs to upgrade its TV system. It is still running
Fedora 10 which is EOL since 2009-12-18:

Still Fedora 10