Snell v6 Installer

中文说明

One-command install, update, and uninstall for Snell v6 on systemd Linux VPS hosts. Keeps your existing config, and stores versioned binaries for safe upgrades and instant rollbacks.

Quick start

Install or update to the latest Snell v6 with a single command:

curl -fsSL https://raw.githubusercontent.com/jizhi0v0/snell-v6-installer/main/snell-v6.sh | sudo bash

That's it. The script auto-detects your CPU, downloads the latest build, writes a config, creates a systemd service, and starts it.

Uninstall just as easily:

curl -fsSL https://raw.githubusercontent.com/jizhi0v0/snell-v6-installer/main/snell-v6-uninstall.sh | sudo bash

Note

Before changing anything, the installer shows a bilingual (English / 中文) summary — detected CPU, current version, target version, download URL, listen address, and mode — and waits for confirmation. On first install it also asks for the listen port (default 7177) and mode (default default).

Why this script

• Safe upgrades & rollbacks — the runtime path /opt/snell/bin/snell-server-v6 is a symlink; real binaries live under /opt/snell/releases/. Upgrades just repoint the symlink, so the old binary is always there to roll back to.
• Your config is preserved — existing settings (PSK, listen, DNS, custom keys like shadow-tls) survive updates untouched.
• Smart version resolution — omit VERSION and it finds the latest v6 build for your CPU, cross-checking a built-in list of known builds against the download server so a freshly published beta or release candidate (like v6.0.0rc) is picked up even before the official release-notes page lists it; refuses accidental downgrades by default.
• Future-proof — works with official beta, RC/RCN, and stable v6 builds that follow upstream naming, from v6.0.0b1 through releases like v6.0.0rc2 and v6.0.0.

What it does, step by step

First install

• Downloads the requested Snell v6 build
• Creates /opt/snell/releases, /opt/snell/bin, and /opt/snell/conf
• Writes /opt/snell/conf/snell-server-v6.conf (if missing)
• Creates and starts the snell-v6 systemd service

Later updates

• Downloads the new build into /opt/snell/releases
• Repoints the /opt/snell/bin/snell-server-v6 symlink
• Keeps the existing config by default
• Restarts snell-v6

Requirements

• Linux VPS with systemd and glibc
• root or sudo

The script can auto-install curl and unzip on apt, dnf, and yum systems.

Configuration

Pass options as environment variables, e.g. sudo env VERSION=v6.0.0rc MODE=unshaped ./snell-v6.sh.

Variable	What it does	Default
VERSION	Target build, e.g. v6.0.0b4, v6.0.0rc, v6.0.0rc2, or v6.0.0 (rc.2 is accepted as a legacy alias)	latest detected v6
SNELL_V6_KNOWN_VERSIONS	Curated builds the auto-resolver verifies when the release notes lag	v6.0.0b1…b4, v6.0.0rc, v6.0.0rc2
ARCH	CPU override: amd64, i386, aarch64 (aliases: x86_64, i686, arm64)	auto-detect
PORT	Listen port (first install only)	7177
PSK	Pre-shared key (first install only)	random 32-char hex
MODE	default, unshaped, or unsafe-raw — requires v6.0.0b3+	default
LISTEN	Full listen address, e.g. 0.0.0.0:7177,[::]:7177	0.0.0.0:<PORT>
DNS_IP_PREFERENCE	e.g. prefer-ipv4	default
CONFIG_OVERWRITE	1 rewrites an existing config (keeps unspecified values)	off
ALLOW_DOWNGRADE	1 permits installing an older version	off
ASSUME_YES	1 skips the confirmation prompt (for automation)	off
PRESERVE_CONFIG	1 keeps /opt/snell when uninstalling	off

Tip

PORT, PSK, LISTEN, MODE, and DNS_* only take effect on first install or when CONFIG_OVERWRITE=1 is set. Normal updates never touch your config.

Subcommands

Read-only helpers that don't change anything:

./snell-v6.sh latest                       # latest detected v6 version
./snell-v6.sh installed                     # currently installed version
./snell-v6.sh download-url                  # resolved download URL
VERSION=v6.0.0rc ./snell-v6.sh arches        # CPU packages available for a version

Note

VERSION=auto, latest, and arches resolve from the official release notes and a curated list of known builds (SNELL_V6_KNOWN_VERSIONS), verifying each candidate against the download server. A just-published build such as v6.0.0rc2 is found even while the release-notes page still lags. Version ordering supports beta, unnumbered RC, numbered RC, and stable builds—for example, v6.0.0b4 < v6.0.0rc < v6.0.0rc1 < v6.0.0rc2 < v6.0.0. If upstream ships something newer than both sources, pin VERSION explicitly (and add it to SNELL_V6_KNOWN_VERSIONS).

Server modes

Snell v6.0.0b3+ adds a server mode (set with MODE). The server and client modes must match.

Mode	Encryption	Obfuscation	Notes
default	✅ AES	✅	Recommended
unshaped	✅ AES	❌	~10% higher throughput
unsafe-raw	❌	❌	Plaintext — see warning below

Warning

unsafe-raw forwards traffic in plaintext. Only use it inside a trusted private network or another secure tunnel.

On first install with v6.0.0b3+, the script asks for the mode interactively (defaults to default). When migrating an older config to v6.0.0b3+, it backs up the config and writes mode = default explicitly. To change the mode on an installed server, use CONFIG_OVERWRITE=1 MODE=....

mode requires a Snell-v6-capable Surge client. For the minimum client build per Snell version, see the official Snell release notes.

Config file reference

Config path: /opt/snell/conf/snell-server-v6.conf

Default for v6.0.0b3+:

[snell-server]
listen = 0.0.0.0:7177
psk = randomly generated 32-character hex string
mode = default
dns-ip-preference = default

• v6.0.0b3+ adds mode; older v6 betas (v6.0.0b2 and earlier) have no mode key.
• Unknown or manually added lines, such as shadow-tls, are preserved during script-managed rewrites.

Matching Surge node:

Snell-V6 = snell, your-server-ip-or-domain, 7177, psk=the-psk-from-config, version=6

Examples

# Install a specific release candidate
sudo env VERSION=v6.0.0rc ./snell-v6.sh

# Numbered release candidates are supported too
sudo env VERSION=v6.0.0rc2 ./snell-v6.sh

# Install for a specific CPU
sudo env VERSION=v6.0.0rc ARCH=aarch64 ./snell-v6.sh

# Custom port and PSK on first install
sudo env PORT=7177 PSK='replace-with-your-own-psk' ./snell-v6.sh

# Enable IPv4 + IPv6 dual-stack listen (rewrites an existing config)
sudo env CONFIG_OVERWRITE=1 LISTEN='0.0.0.0:7177,[::]:7177' ./snell-v6.sh

# Prefer IPv4 for DNS results
sudo env DNS_IP_PREFERENCE=prefer-ipv4 ./snell-v6.sh

# Change mode on an installed server
sudo env CONFIG_OVERWRITE=1 MODE=unshaped ./snell-v6.sh

# Unattended install (no prompt)
sudo env ASSUME_YES=1 VERSION=v6.0.0rc ./snell-v6.sh

# Intentional downgrade
sudo env VERSION=v6.0.0b2 ALLOW_DOWNGRADE=1 ./snell-v6.sh

Note

Downgrading from v6.0.0b3+ to a version without mode support needs CONFIG_OVERWRITE=1 too, so the unsupported mode line can be removed safely: sudo env VERSION=v6.0.0b2 ALLOW_DOWNGRADE=1 CONFIG_OVERWRITE=1 ./snell-v6.sh

Running from a cloned repo? Use chmod +x ./snell-v6.sh then sudo ./snell-v6.sh.

Installed paths

	Path
Binary symlink	/opt/snell/bin/snell-server-v6
Versioned binaries	/opt/snell/releases/snell-server-v6.*
Config	/opt/snell/conf/snell-server-v6.conf
Service	/etc/systemd/system/snell-v6.service

Rollback

Repoint the symlink to an older binary and restart:

sudo ln -sfn /opt/snell/releases/snell-server-v6.0.0b2 /opt/snell/bin/snell-server-v6
sudo systemctl restart snell-v6

Uninstall

# Full uninstall
curl -fsSL https://raw.githubusercontent.com/jizhi0v0/snell-v6-installer/main/snell-v6-uninstall.sh | sudo bash

# Remove the service but keep /opt/snell
curl -fsSL https://raw.githubusercontent.com/jizhi0v0/snell-v6-installer/main/snell-v6-uninstall.sh | sudo env PRESERVE_CONFIG=1 bash

Safety guarantees

The script is conservative by design:

• Configs are preserved by default; it may normalize ownership/mode to root:snell 640 so the service can read it.
• Backups before rewrites — CONFIG_OVERWRITE=1 and service-file replacement create timestamped backups first. If the service can't restart with a rewritten config, the previous config is restored.
• Validated writes — listen ports must be 1–65535; already-listening ports are rejected before any download or service change; IPv6 listen values are rejected when IPv6 looks disabled on the host.
• Binary rollback — if the service fails to restart on a new binary, the symlink is rolled back to the previous version.
• ufw is only touched when already installed; the script never enables it.

Tests

./tests/snell-v6-regression.sh

Covers version ordering, downgrade refusal, port validation, listen parsing, IPv6 rejection, occupied-port detection, mode validation, v6.0.0b2↔v6.0.0b3 migration, config preservation, failed-config restore, and binary rollback.

Upstream references

• Snell v6 blog post
• Official Snell release notes