feat: initial script with readme
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.gitignore
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state/
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images/
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ssh.conf
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52
README.md
52
README.md
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# VM Tool
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This script sets up multiple temporary VMs using QEMU. They run in the background, are on the same network as one another, and can be accessed via SSH.
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## Usage
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Ensure QEMU and `mkisofs` are installed. On Debian-like systems:
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```sh
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sudo apt install qemu-system genisoimage
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```
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Download a base image:
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```sh
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mkdir -p images
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curl -C - -Lo images/Rocky-9-GenericCloud-Base.latest.x86_64.qcow2 https://dl.rockylinux.org/pub/rocky/9/images/x86_64/Rocky-9-GenericCloud-Base.latest.x86_64.qcow2
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```
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Create the VMs (by default, two VMs are created):
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```sh
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./vmtool.sh create
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```
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*Creating VMs will destroy any previous VMs first.*
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Once the VMs are running, access them via SSH:
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```sh
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ssh -F ssh.conf node0
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ssh -F ssh.conf node1
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```
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The VMs are on the same subnet, starting with ip `192.168.30.10` for `node0`, `192.168.30.11` for `node1`, and so on. They can reach one another:
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```console
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[root@node0 ~]# ping 192.168.30.11
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PING 192.168.30.11 (192.168.30.11) 56(84) bytes of data.
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64 bytes from 192.168.30.11: icmp_seq=1 ttl=64 time=0.465 ms
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64 bytes from 192.168.30.11: icmp_seq=2 ttl=64 time=0.390 ms
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64 bytes from 192.168.30.11: icmp_seq=3 ttl=64 time=0.684 ms
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```
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When done, you can stop and/or destroy the VMs:
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```sh
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./vmtool.sh destroy
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```
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## Configuration
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Check the environment variables at the top of the script to set memory, CPU count, max disk size, number of nodes, etc.
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175
vmtool.sh
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175
vmtool.sh
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#!/bin/bash
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# shellcheck disable=SC2155
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# shellcheck disable=SC2164
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readonly script_path="$( cd -- "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )" # https://stackoverflow.com/a/4774063
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# Location of the SSH config to be generated
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SSH_CONFIG=${SSH_CONFIG:-"$script_path/ssh.conf"}
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NUM_NODES=${NUM_NODES:-"2"}
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MEMORY=${MEMORY:-"2048"}
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CPU=${CPU:-"2"}
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DISK_MAX_SIZE=${DISK_MAX_SIZE:-"20G"}
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# Location of VM state information, including its persistent disk
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STATE_DIR=${STATE_DIR:-"$script_path/state"}
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# Location of Linux cloud image
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BASE_IMAGE_FILENAME=${BASE_IMAGE_FILENAME:-"$script_path/images/Rocky-9-GenericCloud-Base.latest.x86_64.qcow2"}
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# Architecture that QEMU will emulate
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EMU_ARCH=${EMU_ARCH:-"x86_64"}
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# Check for prerequisites
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if ! command -v mkisofs > /dev/null 2>&1; then
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echo "mkisofs not found."
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exit 1
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fi
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if ! command -v qemu-system-"$EMU_ARCH" > /dev/null 2>&1; then
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echo "qemu-system-$EMU_ARCH not found."
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exit 1
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fi
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start() {
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for ((i=0;i<NUM_NODES;i++))
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do
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echo "Starting node $i"
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qemu-system-x86_64 \
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-enable-kvm \
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-cpu host \
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-m "$MEMORY" \
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-smp "$CPU" \
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-device virtio-net-pci,netdev=net$i,mac=52:54:00:00:00:"$(printf '%02x' $i)" \
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-netdev socket,id=net$i,mcast=230.0.0.1:1234 \
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-device virtio-net-pci,netdev=host$i \
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-netdev user,id=host$i,hostfwd=tcp::$((3100 + i))-:22 \
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-drive file="$STATE_DIR"/node$i.qcow2,media=disk,if=virtio \
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-drive file="$STATE_DIR"/node$i-cloudinit.iso,media=cdrom \
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-display none \
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-daemonize \
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-pidfile "$STATE_DIR"/node$i.pid
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done
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for ((i=0;i<NUM_NODES;i++))
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do
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local attempts_remaining=10
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while ! ssh -o ConnectTimeout=2 -o BatchMode=true -F "$SSH_CONFIG" node$i exit >/dev/null 2>&1 && ((attempts_remaining > 0));
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do
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((attempts_remaining--))
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if [ $attempts_remaining == 0 ]; then
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echo "SSH service on node$i took too long to be ready"
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exit 1
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fi
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echo "Waiting for SSH service on node$i to be ready; $attempts_remaining attempts remaining"
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sleep 5
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done
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echo "SSH service on node$i is up"
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done
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echo "To access a VM, run:"
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echo
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echo " ssh -F $SSH_CONFIG node#"
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echo
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echo "Where # is the node number you want to reach."
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}
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stop() {
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for ((i=0;i<NUM_NODES;i++))
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do
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pkill -F "$STATE_DIR"/node$i.pid >/dev/null 2>&1
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rm -f "$STATE_DIR"/node$i.pid
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done
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}
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destroy() {
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stop
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rm -f "$STATE_DIR"/id_ed25519
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rm -f "$STATE_DIR"/id_ed25519.pub
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rm -f "$SSH_CONFIG"
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for ((i=0;i<NUM_NODES;i++))
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do
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rm -f "$STATE_DIR"/node$i-cloudinit.iso
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rm -f "$STATE_DIR"/node$i.qcow2
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done
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}
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create() {
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destroy
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mkdir -p "$STATE_DIR"
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ssh-keygen -f qemu_key -N "" -t ed25519 -C "" -f "$STATE_DIR"/id_ed25519 >/dev/null 2>&1
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ssh_pubkey=$(tr -d '\n' < "$STATE_DIR"/id_ed25519.pub)
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for ((i=0;i<NUM_NODES;i++))
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do
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# Create cloud-init volume
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cat > "$STATE_DIR"/user-data <<- EOF
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#cloud-config
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users:
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- name: root
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ssh_authorized_keys:
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- $ssh_pubkey
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EOF
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cat > "$STATE_DIR"/meta-data <<- EOF
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instance-id: node$i
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local-hostname: node$i
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EOF
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cat > "$STATE_DIR"/network-config <<- EOF
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network:
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version: 2
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ethernets:
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eth0:
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match:
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macaddress: "52:54:00:00:00:$(printf '%02x' $i)"
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dhcp4: false
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addresses:
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- 192.168.30.$((10 + i))/24
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EOF
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mkisofs -o "$STATE_DIR"/node$i-cloudinit.iso -V cidata -r -J "$STATE_DIR"/user-data "$STATE_DIR"/meta-data "$STATE_DIR"/network-config >/dev/null 2>&1
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rm "$STATE_DIR"/user-data
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rm "$STATE_DIR"/meta-data
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rm "$STATE_DIR"/network-config
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# Create main disk, backed by read-only cloud image
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qemu-img create -f qcow2 -F qcow2 -b "$BASE_IMAGE_FILENAME" "$STATE_DIR"/node$i.qcow2 20G >/dev/null 2>&1
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# Create SSH config to be used for accessing the VM
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cat >> "$SSH_CONFIG" <<- EOF
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Host node$i
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StrictHostKeyChecking no
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UserKnownHostsFile /dev/null
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IdentityFile $STATE_DIR/id_ed25519
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IdentitiesOnly yes
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User root
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Hostname localhost
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Port $((3100 + i))
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EOF
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done
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start
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}
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case $1 in
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stop)
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shift
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stop "$@"
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;;
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destroy)
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shift
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destroy "$@"
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;;
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create)
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shift
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create "$@"
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;;
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esac
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