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