lix/scripts/install-systemd-multi-user.sh
Rovanion Luckey a413594baf installer: Handle edge case where the nix-daemon is already running on the system
On a systemd-based Linux distribution: If the user has previously had multi-user Nix installed on the system, removed it and then reinstalled multi-user Nix again the old nix-daemon.service will still be running when `scripts/install-systemd-multi-user.sh` tries to start it which results in nothing being done and the old daemon continuing its run.

When a normal user then tries to use Nix through the daemon the nix binary will fail to connect to the nix-daemon as it does not belong to the currently installed Nix system. See below for steps to reproduce the issue that motivated this change.

$ sh <(curl https://nixos.org/nix/install) --daemon

$ sudo rm -rf /etc/nix /nix /root/.nix-profile /root/.nix-defexpr /root/.nix-channels /home/nix-installer/.nix-profile /home/nix-installer/.nix-defexpr /home/nix-installer/.nix-channels ~/.nix-channels ~/.nix-defexpr/ ~/.nix-profile /etc/profile.d/nix.sh.backup-before-nix /etc/profile.d/nix.sh; sed -i '/added by Nix installer$/d' ~/.bash_profile

$ unset NIX_REMOTE

$ sh <(curl https://nixos.org/nix/install) --daemon

└$ export NIX_REMOTE=daemon

└$ nix-env -iA nixpkgs.hello
installing 'hello-2.10'
error: cannot connect to daemon at '/nix/var/nix/daemon-socket/socket': No such file or directory
(use '--show-trace' to show detailed location information)

└$ sudo systemctl restart nix-daemon.service

└$ nix-env -iA nixpkgs.hello
installing 'hello-2.10'
these paths will be fetched (6.09 MiB download, 27.04 MiB unpacked):
  /nix/store/2g75chlbpxlrqn15zlby2dfh8hr9qwbk-hello-2.10
  /nix/store/aag9d1y4wcddzzrpfmfp9lcmc7skd7jk-glibc-2.27
copying path '/nix/store/aag9d1y4wcddzzrpfmfp9lcmc7skd7jk-glibc-2.27' from 'https://cache.nixos.org'...
copying path '/nix/store/2g75chlbpxlrqn15zlby2dfh8hr9qwbk-hello-2.10' from 'https://cache.nixos.org'...
building '/nix/store/w9adagg6vlikr799nkkqc9la5hbbpgmi-user-environment.drv'...
created 2 symlinks in user environment
2020-01-23 14:48:53 +01:00

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#!/usr/bin/env bash
set -eu
set -o pipefail
readonly SERVICE_SRC=/lib/systemd/system/nix-daemon.service
readonly SERVICE_DEST=/etc/systemd/system/nix-daemon.service
readonly SOCKET_SRC=/lib/systemd/system/nix-daemon.socket
readonly SOCKET_DEST=/etc/systemd/system/nix-daemon.socket
# Path for the systemd override unit file to contain the proxy settings
readonly SERVICE_OVERRIDE=${SERVICE_DEST}.d/override.conf
create_systemd_override() {
header "Configuring proxy for the nix-daemon service"
_sudo "create directory for systemd unit override" mkdir -p "$(dirname $SERVICE_OVERRIDE)"
cat <<EOF | _sudo "create systemd unit override" tee "$SERVICE_OVERRIDE"
[Service]
$1
EOF
}
# Gather all non-empty proxy environment variables into a string
create_systemd_proxy_env() {
vars="http_proxy https_proxy ftp_proxy no_proxy HTTP_PROXY HTTPS_PROXY FTP_PROXY NO_PROXY"
for v in $vars; do
if [ "x${!v:-}" != "x" ]; then
echo "Environment=${v}=${!v}"
fi
done
}
handle_network_proxy() {
# Create a systemd unit override with proxy environment variables
# if any proxy environment variables are not empty.
PROXY_ENV_STRING=$(create_systemd_proxy_env)
if [ -n "${PROXY_ENV_STRING}" ]; then
create_systemd_override "${PROXY_ENV_STRING}"
fi
}
poly_validate_assumptions() {
if [ "$(uname -s)" != "Linux" ]; then
failure "This script is for use with Linux!"
fi
}
poly_service_installed_check() {
[ "$(systemctl is-enabled nix-daemon.service)" = "linked" ] \
|| [ "$(systemctl is-enabled nix-daemon.socket)" = "enabled" ]
}
poly_service_uninstall_directions() {
cat <<EOF
$1. Delete the systemd service and socket units
sudo systemctl stop nix-daemon.socket
sudo systemctl stop nix-daemon.service
sudo systemctl disable nix-daemon.socket
sudo systemctl disable nix-daemon.service
sudo systemctl daemon-reload
EOF
}
poly_service_setup_note() {
cat <<EOF
- load and start a service (at $SERVICE_DEST
and $SOCKET_DEST) for nix-daemon
EOF
}
poly_configure_nix_daemon_service() {
_sudo "to set up the nix-daemon service" \
systemctl link "/nix/var/nix/profiles/default$SERVICE_SRC"
_sudo "to set up the nix-daemon socket service" \
systemctl enable "/nix/var/nix/profiles/default$SOCKET_SRC"
handle_network_proxy
_sudo "to load the systemd unit for nix-daemon" \
systemctl daemon-reload
_sudo "to start the nix-daemon.socket" \
systemctl start nix-daemon.socket
_sudo "to start the nix-daemon.service" \
systemctl restart nix-daemon.service
}
poly_group_exists() {
getent group "$1" > /dev/null 2>&1
}
poly_group_id_get() {
getent group "$1" | cut -d: -f3
}
poly_create_build_group() {
_sudo "Create the Nix build group, $NIX_BUILD_GROUP_NAME" \
groupadd -g "$NIX_BUILD_GROUP_ID" --system \
"$NIX_BUILD_GROUP_NAME" >&2
}
poly_user_exists() {
getent passwd "$1" > /dev/null 2>&1
}
poly_user_id_get() {
getent passwd "$1" | cut -d: -f3
}
poly_user_hidden_get() {
echo "1"
}
poly_user_hidden_set() {
true
}
poly_user_home_get() {
getent passwd "$1" | cut -d: -f6
}
poly_user_home_set() {
_sudo "in order to give $1 a safe home directory" \
usermod --home "$2" "$1"
}
poly_user_note_get() {
getent passwd "$1" | cut -d: -f5
}
poly_user_note_set() {
_sudo "in order to give $1 a useful comment" \
usermod --comment "$2" "$1"
}
poly_user_shell_get() {
getent passwd "$1" | cut -d: -f7
}
poly_user_shell_set() {
_sudo "in order to prevent $1 from logging in" \
usermod --shell "$2" "$1"
}
poly_user_in_group_check() {
groups "$1" | grep -q "$2" > /dev/null 2>&1
}
poly_user_in_group_set() {
_sudo "Add $1 to the $2 group"\
usermod --append --groups "$2" "$1"
}
poly_user_primary_group_get() {
getent passwd "$1" | cut -d: -f4
}
poly_user_primary_group_set() {
_sudo "to let the nix daemon use this user for builds (this might seem redundant, but there are two concepts of group membership)" \
usermod --gid "$2" "$1"
}
poly_create_build_user() {
username=$1
uid=$2
builder_num=$3
_sudo "Creating the Nix build user, $username" \
useradd \
--home-dir /var/empty \
--comment "Nix build user $builder_num" \
--gid "$NIX_BUILD_GROUP_ID" \
--groups "$NIX_BUILD_GROUP_NAME" \
--no-user-group \
--system \
--shell /sbin/nologin \
--uid "$uid" \
--password "!" \
"$username"
}