Add execute-pre option

Allows to execute a command before the guest server starts.
Useful on distros like NixOS where we need additional mounts.

Signed-off-by: Nikodem Rabuliński <[email protected]>

Author: nrabulinski

README.md

@@ -13,7 +13,7 @@
 ``` sh
 Usage: muvm [-c=CPU_LIST]... [-e=ENV]... [--mem=MEM] [--vram=VRAM] [--passt-socket=PATH] [-f=
 FEX_IMAGE]... [-m] [-i] [-t] [--privileged] [-p=<[[IP:][HOST_PORT]:]GUEST_PORT[/PROTOCOL]>]... [
---emu=EMU] COMMAND [COMMAND_ARGS]...
+--emu=EMU] [-x=COMMAND]... COMMAND [COMMAND_ARGS]...
 
 Available positional items:
     COMMAND                  the command you want to execute in the vm
@@ -56,6 +56,8 @@ Available options:
                                       Valid options are "box" and "fex". If this argument is not
                                       present, muvm will try to use FEX, falling back to Box if it
                                       can't be found.
+    -x, --execute-pre=COMMAND  Command to run inside the VM before guest server starts.
+                                     Can be used for e.g. setting up additional mounts. Can be specified many times
     -h, --help               Prints help information
 ```
 

crates/muvm/src/bin/muvm.rs

@@ -389,6 +389,7 @@ fn main() -> Result<ExitCode> {
         host_display: display,
         merged_rootfs: options.merged_rootfs,
         emulator: options.emulator,
+        init_commands: options.init_commands,
     };
     let mut muvm_config_file = NamedTempFile::new()
         .context("Failed to create a temporary file to store the muvm guest config")?;

crates/muvm/src/cli_options.rs

@@ -21,6 +21,7 @@ pub struct Options {
     pub privileged: bool,
     pub publish_ports: Vec<String>,
     pub emulator: Option<Emulator>,
+    pub init_commands: Vec<PathBuf>,
     pub command: PathBuf,
     pub command_args: Vec<String>,
 }
@@ -132,6 +133,14 @@ pub fn options() -> OptionParser<Options> {
         )
         .argument::<String>("[[IP:][HOST_PORT]:]GUEST_PORT[/PROTOCOL]")
         .many();
+    let init_commands = long("execute-pre")
+        .short('x')
+        .help(
+            "Command to run inside the VM before guest server starts.
+            Can be used for e.g. setting up additional mounts. Can be specified many times",
+        )
+        .argument("COMMAND")
+        .many();
     let command = positional("COMMAND").help("the command you want to execute in the vm");
     let command_args = any::<String, _, _>("COMMAND_ARGS", |arg| {
         (!["--help", "-h"].contains(&&*arg)).then_some(arg)
@@ -152,6 +161,7 @@ pub fn options() -> OptionParser<Options> {
         privileged,
         publish_ports,
         emulator,
+        init_commands,
         // positionals
         command,
         command_args,

crates/muvm/src/guest/bin/muvm-guest.rs

@@ -2,10 +2,10 @@ use std::fs::File;
 use std::io::Read;
 use std::os::fd::AsFd;
 use std::panic::catch_unwind;
-use std::process::Command;
+use std::process::{Command, Stdio};
 use std::{cmp, env, fs, thread};
 
-use anyhow::{Context, Result};
+use anyhow::{anyhow, Context, Result};
 use muvm::guest::box64::setup_box;
 use muvm::guest::bridge::pipewire::start_pwbridge;
 use muvm::guest::bridge::x11::start_x11bridge;
@@ -94,6 +94,18 @@ fn main() -> Result<()> {
         }
     }
 
+    for init_command in options.init_commands {
+        let code = Command::new(&init_command)
+            .stdin(Stdio::null())
+            .stdout(Stdio::piped())
+            .stderr(Stdio::piped())
+            .spawn()?
+            .wait()?;
+        if !code.success() {
+            return Err(anyhow!("Executing `{}` failed", init_command.display()));
+        }
+    }
+
     configure_network()?;
 
     let run_path = match setup_user(Uid::from(options.uid), Gid::from(options.gid)) {

crates/muvm/src/utils/launch.rs

@@ -43,6 +43,7 @@ pub struct GuestConfiguration {
     pub host_display: Option<String>,
     pub merged_rootfs: bool,
     pub emulator: Option<Emulator>,
+    pub init_commands: Vec<PathBuf>,
 }
 
 pub const PULSE_SOCKET: u32 = 3333;