---
title: "Shared Server"
canonical_url: https://www.superlogical.com/rex/docs/linux/shared-server
---

# Shared Server

The shared server is one Rex server that runs as the `rex` system account,
as `rex.service`. Members of the `rex` group can connect to it, and every
program they start runs as `rex`. It's the simplest
[server mode](https://www.superlogical.com/rex/docs/linux/server-modes.md) for a few people who are comfortable
sharing one account.

**Access to the shared server is access to the `rex` account.** Anyone in
the group can see and type into every session on it and start programs as
`rex`. Only add people you would trust with that account. If people need
their own files and permissions, use the [login server](https://www.superlogical.com/rex/docs/linux/login-server.md)
instead.

## Starting the Server

The package creates the `rex` account with `nologin` as its shell, and Rex
starts each terminal with its account's shell. Give the account a real
shell first, or every terminal on the shared server exits as soon as it
starts:

```sh
sudo usermod --shell /bin/bash rex
```

Alpine has neither `usermod` nor bash by default. Install `usermod` with
the `shadow` package and use `/bin/sh`:

```sh
apk add shadow
usermod --shell /bin/sh rex
```

The account stays locked, with no password, so nobody can log in as `rex`
this way.

Then start the service now and at every boot:

```sh
sudo systemctl enable --now rex.service
```

On Alpine, run `rc-update add rex`, then `rc-service rex start`.

The server listens on `/run/rex/server.sock` and keeps its data in
`/var/lib/rex`, the `rex` account's home directory.

## Giving People Access

Add each person to the `rex` group. The change applies the next time they
log in:

```sh
sudo usermod --append --groups rex alice
```

On Alpine, run `addgroup alice rex`.

Their `rex` commands look for their own [personal
server](https://www.superlogical.com/rex/docs/linux/server-modes.md#personal-server) by default, and start one if
it isn't running. To use the shared server instead, pass its socket with
`-S`, or set `REX_SERVER` in their shell profile so every `rex` command
uses it:

```sh
rex -S /run/rex/server.sock ls
export REX_SERVER=/run/rex/server.sock
```

Inside the shared server's own terminals, `rex` commands already use the
shared server.

The service isn't sandboxed on purpose. Sandboxing would also restrict the
programs people run in it, so the `rex` account is the security boundary.

To reach the shared server from another computer, see
[Remote Access](https://www.superlogical.com/rex/docs/linux/remote-access.md).

## Configuration

The shared server reads its [configuration file](https://www.superlogical.com/rex/docs/customize/config.md) from
the `rex` account's home:

```
/var/lib/rex/.config/rex/init.lua
```

Only root can edit it, because `/var/lib/rex` is private to the `rex`
account. After you change it, any member of the group can reload it:

```sh
sudo $EDITOR /var/lib/rex/.config/rex/init.lua
rex -S /run/rex/server.sock config reload
```

To keep the file somewhere else, pass `--config PATH` in a drop-in, as
below.

## Customizing the Service

Package upgrades replace `rex.service`, so put changes in a drop-in file
instead. This command creates one and opens it in your editor:

```sh
sudo systemctl edit rex.service
```

To change the server's options, clear `ExecStart` and set it again. This
example raises the session limit:

```ini
[Service]
ExecStart=
ExecStart=/usr/bin/rex server run --listen /run/rex/server.sock \
  --state-dir /var/lib/rex --socket-mode 0660 --log-format text \
  --max-sessions 128
```

On Alpine, upgrades replace `/etc/init.d/rex`, so set `command_args` in
`/etc/conf.d/rex` instead. The package never creates or changes that file.
The same example there leaves out `/usr/bin/rex`:

```sh
command_args="server run --listen /run/rex/server.sock \
  --state-dir /var/lib/rex --socket-mode 0660 --log-format text \
  --max-sessions 128"
```

Keep the four options from the original command line. The same pattern adds
a network listener for [Remote Access](https://www.superlogical.com/rex/docs/linux/remote-access.md) or a block
plugin directory with `--block-dir`. Run `rex server run --help` for every
option.

## Logs

The shared server logs to the journal:

```sh
journalctl -u rex.service -f
```

Alpine has no journal, so there the server logs to a file:

```sh
tail -f /var/log/rex/server.log
```

The logs are plain text. For JSON, change `--log-format text` to
`--log-format json` in a drop-in.

## Upgrading

Upgrading the package restarts a running shared server, so it runs the new
version right away.

**Restarting ends every session and every program in them.** Upgrade when
nobody has work running, or
[hold the package](https://www.superlogical.com/rex/docs/linux/upgrading.md#holding-an-upgrade) until then.

The login server doesn't have this problem. Its sessions survive upgrades.
[Upgrading](https://www.superlogical.com/rex/docs/linux/upgrading.md) covers the rest.