adding HOME into envs when init containers (#681)

* WIP: adding HOME into envs when init containers

Signed-off-by: Hugo Wang <w@mitnk.com>

build.sh

@@ -16,9 +16,9 @@ fi
 # not a part of youki workspace. For the reasoning behind this,
 # please check the docs and readme
 
-cargo build --verbose $TGT $1
+cargo build $TGT $1 $2
 cd ./runtimetest
-cargo build --verbose $TGT $1
+cargo build $TGT $1 $2
 cd ..
 
 cp target/$TARGET/$VERSION/youki .

crates/libcontainer/src/process/container_init_process.rs

@@ -412,8 +412,16 @@ pub fn container_init_process(
         unistd::chdir(proc.cwd()).with_context(|| format!("failed to chdir {:?}", proc.cwd()))?;
     }
 
+    // add HOME into envs if not exists
+    let home_in_envs = envs.iter().any(|x| x.starts_with("HOME="));
+    if !home_in_envs {
+        if let Some(dir_home) = utils::get_user_home(proc.user().uid()) {
+            envs.push(format!("HOME={}", dir_home.to_string_lossy()));
+        }
+    }
+
     // Reset the process env based on oci spec.
-    env::vars().for_each(|(key, _value)| std::env::remove_var(key));
+    env::vars().for_each(|(key, _value)| env::remove_var(key));
     utils::parse_env(&envs)
         .iter()
         .for_each(|(key, value)| env::set_var(key, value));

crates/libcontainer/src/utils.rs

@@ -5,6 +5,7 @@ use anyhow::{bail, Result};
 use nix::sys::stat::Mode;
 use nix::sys::statfs;
 use nix::unistd;
+use nix::unistd::{Uid, User};
 use std::collections::HashMap;
 use std::ffi::CString;
 use std::fs::{self, DirBuilder, File};
@@ -56,6 +57,22 @@ pub fn parse_env(envs: &[String]) -> HashMap<String, String> {
         .collect()
 }
 
+/// Get a nix::unistd::User via UID. Potential errors will be ignored.
+pub fn get_unix_user(uid: Uid) -> Option<User> {
+    match User::from_uid(uid) {
+        Ok(x) => x,
+        Err(_) => None,
+    }
+}
+
+/// Get home path of a User via UID.
+pub fn get_user_home(uid: u32) -> Option<PathBuf> {
+    match get_unix_user(Uid::from_raw(uid)) {
+        Some(user) => Some(user.dir),
+        None => None,
+    }
+}
+
 pub fn do_exec(path: impl AsRef<Path>, args: &[String]) -> Result<()> {
     let p = CString::new(path.as_ref().as_os_str().as_bytes())
         .with_context(|| format!("failed to convert path {:?} to cstring", path.as_ref()))?;
@@ -318,6 +335,26 @@ pub(crate) mod test_utils {
 mod tests {
     use super::*;
 
+    #[test]
+    pub fn test_get_unix_user() {
+        let user = get_unix_user(Uid::from_raw(0));
+        assert_eq!(user.unwrap().name, "root");
+
+        // for a non-exist UID
+        let user = get_unix_user(Uid::from_raw(1000000000));
+        assert!(user.is_none());
+    }
+
+    #[test]
+    pub fn test_get_user_home() {
+        let dir = get_user_home(0);
+        assert_eq!(dir.unwrap().to_str().unwrap(), "/root");
+
+        // for a non-exist UID
+        let dir = get_user_home(1000000000);
+        assert!(dir.is_none());
+    }
+
     #[test]
     fn test_get_cgroup_path() {
         let cid = "sample_container_id";

docs/src/user/basic_usage.md

@@ -56,6 +56,26 @@ Then to start the original/normal Docker daemon, you can run
 sudo systemctl start docker
 ```
 
+#### Let docker permanently know youki as a runtime
+
+With newer versions of docker, you can update file `/etc/docker/daemon.json` to
+let docker know youki
+([source](https://docs.docker.com/engine/reference/commandline/dockerd/#on-linux)).
+A sample content of it:
+```
+{
+  "default-runtime": "runc",
+  "runtimes": {
+    "youki": {
+      "path": "/path/to/youki/youki"
+    }
+  }
+}
+```
+
+After this (need to restart docker at the first time), you can use youki
+with docker: `docker run --runtime youki ...`.
+
 #### Using Youki Standalone
 
 Youki can also be used directly, without a higher-level runtime such as Docker to create, start, stop and delete the container, but the process can be tedious. Here we will show how you can do that, to run a simple container with desired program running in it.