Adding upstream version 252.22.upstream/252.22upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+---
+title: Converting Existing Users to systemd-homed
+category: Users, Groups and Home Directories
+layout: default
+SPDX-License-Identifier: LGPL-2.1-or-later
+---
+
+# Converting Existing Users to systemd-homed managed Users
+
+Traditionally on most Linux distributions, regular (human) users are managed
+via entries in `/etc/passwd`, `/etc/shadow`, `/etc/group` and
+`/etc/gshadow`. With the advent of
+[`systemd-homed`](https://www.freedesktop.org/software/systemd/man/systemd-homed.service.html)
+it might be desirable to convert an existing, traditional user account to a
+`systemd-homed` managed one. Below is a brief guide how to do that.
+
+Before continuing, please read up on these basic concepts:
+
+* [Home Directories](HOME_DIRECTORY.md)
+* [JSON User Records](USER_RECORD.md)
+* [JSON Group Records](GROUP_RECORD.md)
+* [User/Group Record Lookup API via Varlink](USER_GROUP_API.md)
+
+## Caveat
+
+This is a manual process, and possibly a bit fragile. Hence, do this at your
+own risk, read up beforehand, and make a backup first. You know what's at
+stake: your own home directory, i.e. all your personal data.
+
+## Step-By-Step
+
+Here's the step-by-step guide:
+
+0. Preparations: make sure you run a distribution that has `systemd-homed`
+   enabled and properly set up, including the necessary PAM and NSS
+   configuration updates. Make sure you have enough disk space in `/home/` for
+   a (temporary) second copy of your home directory. Make sure to backup your
+   home directory. Make sure to log out of your user account fully. Then log in
+   as root on the console.
+
+1. Rename your existing home directory to something safe. Let's say your user
+   ID is `foobar`. Then do:
+
+    ```
+    mv /home/foobar /home/foobar.saved
+    ```
+
+2. Have a look at your existing user record, as stored in `/etc/passwd` and
+   related files. We want to use the same data for the new record, hence it's good
+   looking at the old data. Use commands such as:
+
+    ```
+    getent passwd foobar
+    getent shadow foobar
+    ```
+
+   This will tell you the `/etc/passwd` and `/etc/shadow` entries for your
+   user. For details about the fields, see the respective man pages
+   [passwd(5)](https://man7.org/linux/man-pages/man5/passwd.5.html) and
+   [shadow(5)](https://man7.org/linux/man-pages/man5/shadow.5.html).
+
+   The fourth field in the `getent passwd foobar` output tells you the GID of
+   your user's main group. Depending on your distribution it's a group private
+   to the user, or a group shared by most local, regular users. Let's say the
+   GID reported is 1000, let's then query its details:
+
+    ```
+    getent group 1000
+    ```
+
+   This will tell you the name of that group. If the name is the same as your
+   user name your distribution apparently provided you with a private group for
+   your user. If it doesn't match (and is something like `users`) it apparently
+   didn't. Note that `systemd-homed` will always manage a private group for
+   each user under the same name, hence if your distribution is one of the
+   latter kind, then there's a (minor) mismatch in structure when converting.
+
+   Save the information reported by these three commands somewhere, for later
+   reference.
+
+3. Now edit your `/etc/passwd` file and remove your existing record
+   (i.e. delete a single line, the one of your user's account, leaving all
+   other lines unmodified). Similar for `/etc/shadow`, `/etc/group` (in case
+   you have a private group for your user) and `/etc/gshadow`. Most
+   distributions provide you with a tool for that, that adds safe
+   synchronization for these changes: `vipw`, `vipw -s`, `vigr` and `vigr -s`.
+
+4. At this point the old user account vanished, while the home directory still
+   exists safely under the `/home/foobar.saved` name. Let's now create a new
+   account with `systemd-homed`, using the same username and UID as before:
+
+    ```
+    homectl create foobar --uid=$UID --real-name=$GECOS
+    ```
+
+   In this command line, replace `$UID` by the UID you previously used,
+   i.e. the third field of the `getent passwd foobar` output above. Similar,
+   replace `$GECOS` by the GECOS field of your old account, i.e the fifth field
+   of the old output. If your distribution traditionally does not assign a
+   private group to regular user groups, then consider adding `--member-of=`
+   with the group name to get a modicum of compatibility with the status quo
+   ante: this way your new user account will still not have the old primary
+   group as new primary group, but will have it as auxiliary group.
+
+   Consider reading through the
+   [homectl(1)](https://www.freedesktop.org/software/systemd/man/homectl.html)
+   manual page at this point, maybe there are a couple of other settings you
+   want to set for your new account. In particular, look at `--storage=` and
+   `--disk-size=`, in order to change how your home directory shall be stored
+   (the default `luks` storage is recommended).
+
+5. Your new user account exists now, but it has an empty home directory. Let's
+   now migrate your old home directory into it. For that let's mount the new
+   home directory temporarily and copy the data in.
+
+    ```
+    homectl with foobar -- rsync -aHAXv --remove-source-files /home/foobar.saved/ .
+    ```
+
+   This mounts the home directory of the user, and then runs the specified
+   `rsync` command which copies the contents of the old home directory into the
+   new. The new home directory is the working directory of the invoked `rsync`
+   process. We are invoking this command as root, hence the `rsync` runs as
+   root too. When the `rsync` command completes the home directory is
+   automatically unmounted again. Since we used `--remove-source-files` all files
+   copied are removed from the old home directory as the copy progresses. After
+   the command completes the old home directory should be empty. Let's remove
+   it hence:
+
+    ```
+    rmdir /home/foobar.saved
+    ```
+
+And that's it, we are done already. You can log out now and should be able to
+log in under your user account as usual, but now with `systemd-homed` managing
+your home directory.