fix: use temp file to write config

[ryota-sakamoto]

Issue #, if available:

#172

Description of changes:

We use temp file to generate default config. Because while fs::write is writing the contents to default config path, serde_yaml::from_str return EndOfStream.

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[StoneDot]

Thank you for creating PR. I left nits comments. Would you take a look at them?

[StoneDot]

I came up with the case where the /home directory uses a different disk. So, I tried the following. Its result indicates that we should create a temporary file in the same directory as config uses. Could you change the code to use the same directory instead of NamedTempFile?

1. Download Ubuntu Server 22.04.3 LTS ISO image.
2. Create a virtual machine using (A).
3. Connect VM using virt-viewer dynein_check and follow (B).
4. Detach media after the installation using virsh change-media dynein_check sda --eject.
5. VM goes shutdown.
6. Restart vm using virsh start dynein_check and connect virt-viewer dynein_check.
7. Run test for dynein (C)

(A)

virt-install -n dynein_check -r 8192 \
  --disk path=$HOME/vm/dynein_root.img,bus=virtio,size=20 \
  --disk path=$HOME/vm/dynein_home.img,bus=virtio,size=20 \
  -c ubuntu-22.04.3-live-server-amd64.iso \
  --network network=default,model=virtio \
  --graphics vnc,listen=0.0.0.0 --noautoconsole -v --vcpus=2

(B)
Install default Ubuntu Server with custom storage layout.

• /dev/vda
  • partition 1 new, BIOS group spacer 1.000M
  • partition 2 new, to be formatted as ext4, mounted at /
• /dev/vdb
  • partition 1 new, to be formatted as ext4, mounted at /home

(C)

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
# Use default installation
source "$HOME/.cargo/env"
sudo apt-get update
sudo apt install git gcc pkg-config libssl-dev docker -y
sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
sudo chmod a+r /etc/apt/keyrings/docker.gpg
echo "deb [arch=amd64 signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu   jammy stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin -y
git clone https://github.com/awslabs/dynein.git
cd dynein
sudo docker run -p 8000:8000 -d amazon/dynamodb-local
export RUST_BACKTRACE=1
export AWS_ACCESS_KEY_ID=test
export AWS_SECRET_ACCESS_KEY=test
cargo run ls -r local
cargo run admin create table test1 --keys pk -r local
cargo run use test -r local
# These should succeed
git remote add ryota-sakamoto https://github.com/ryota-sakamoto/dynein.git
git fetch --all
git checkout ryota-sakamoto/fix-generate-config
cargo run ls -r local
cargo run admin create table test2 --keys pk -r local
cargo run use test2 -r local

This causes the following error;

Error: IO(Os { code: 18, kind: CrossesDevices, message: "Invalid cross-device link" })

[ryota-sakamoto]

@StoneDot
I have fixed the point you commented. I am using NamedTempFile::new_in instead of NamedTempFile::new to generate temporary file into dynein dir.

[StoneDot]

Thank you for the improvement. LGTM