composefs/state: Name state directory default

Instead of `/sysroot/state/os/fedora` use `/sysroot/state/os/default` as
the default state directory.

Signed-off-by: Johan-Liebert1 <pragyanpoudyal41999@gmail.com>

Author: Johan-Liebert1

crates/lib/src/composefs_consts.rs

@@ -10,6 +10,8 @@ pub(crate) const COMPOSEFS_STAGED_DEPLOYMENT_FNAME: &str = "staged-deployment";
 pub(crate) const STATE_DIR_ABS: &str = "/sysroot/state/deploy";
 /// Relative path to composefs-native state directory. Relative to /sysroot
 pub(crate) const STATE_DIR_RELATIVE: &str = "state/deploy";
+/// Relative path to the shared 'var' directory. Relative to /sysroot
+pub(crate) const SHARED_VAR_PATH: &str = "state/os/default/var";
 
 /// Section in .origin file to store boot related metadata
 pub(crate) const ORIGIN_KEY_BOOT: &str = "boot";

crates/lib/src/install.rs

@@ -78,7 +78,8 @@ use crate::boundimage::{BoundImage, ResolvedBoundImage};
 use crate::composefs_consts::{
     BOOT_LOADER_ENTRIES, COMPOSEFS_CMDLINE, COMPOSEFS_STAGED_DEPLOYMENT_FNAME,
     COMPOSEFS_TRANSIENT_STATE_DIR, ORIGIN_KEY_BOOT, ORIGIN_KEY_BOOT_DIGEST, ORIGIN_KEY_BOOT_TYPE,
-    STAGED_BOOT_LOADER_ENTRIES, STATE_DIR_ABS, STATE_DIR_RELATIVE, USER_CFG, USER_CFG_STAGED,
+    SHARED_VAR_PATH, STAGED_BOOT_LOADER_ENTRIES, STATE_DIR_ABS, STATE_DIR_RELATIVE, USER_CFG,
+    USER_CFG_STAGED,
 };
 use crate::containerenv::ContainerExecutionInfo;
 use crate::deploy::{
@@ -92,7 +93,7 @@ use crate::progress_jsonl::ProgressWriter;
 use crate::spec::ImageReference;
 use crate::store::Storage;
 use crate::task::Task;
-use crate::utils::sigpolicy_from_opt;
+use crate::utils::{path_relative_to, sigpolicy_from_opt};
 use bootc_mount::{inspect_filesystem, Filesystem};
 
 /// The toplevel boot directory
@@ -2198,11 +2199,15 @@ pub(crate) fn write_composefs_state(
     create_dir_all(state_path.join("etc/upper"))?;
     create_dir_all(state_path.join("etc/work"))?;
 
-    let actual_var_path = root_path.join(format!("state/os/fedora/var"));
+    let actual_var_path = root_path.join(SHARED_VAR_PATH);
     create_dir_all(&actual_var_path)?;
 
-    symlink(Path::new("../../os/fedora/var"), state_path.join("var"))
-        .context("Failed to create symlink for /var")?;
+    symlink(
+        path_relative_to(state_path.as_std_path(), actual_var_path.as_std_path())
+            .context("Getting var symlink path")?,
+        state_path.join("var"),
+    )
+    .context("Failed to create symlink for /var")?;
 
     let ImageReference {
         image: image_name,

crates/lib/src/utils.rs

@@ -1,8 +1,9 @@
-use std::future::Future;
 use std::io::Write;
 use std::os::fd::BorrowedFd;
+use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::time::Duration;
+use std::{future::Future, path::Component};
 
 use anyhow::{Context, Result};
 use bootc_utils::CommandRunExt;
@@ -186,6 +187,28 @@ pub(crate) fn digested_pullspec(image: &str, digest: &str) -> String {
     format!("{image}@{digest}")
 }
 
+/// Computes a relative path from `from` to `to`.
+///
+/// Both `from` and `to` must be absolute paths.
+pub(crate) fn path_relative_to(from: &Path, to: &Path) -> Result<PathBuf> {
+    if !from.is_absolute() || !to.is_absolute() {
+        anyhow::bail!("Paths must be absolute");
+    }
+
+    let from = from.components().collect::<Vec<_>>();
+    let to = to.components().collect::<Vec<_>>();
+
+    let common = from.iter().zip(&to).take_while(|(a, b)| a == b).count();
+
+    let up = std::iter::repeat(Component::ParentDir).take(from.len() - common);
+
+    let mut final_path = PathBuf::new();
+    final_path.extend(up);
+    final_path.extend(&to[common..]);
+
+    return Ok(final_path);
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -223,4 +246,21 @@ mod tests {
             SignatureSource::ContainerPolicyAllowInsecure
         );
     }
+
+    #[test]
+    fn test_relative_path() {
+        let from = Path::new("/sysroot/state/deploy/image_id");
+        let to = Path::new("/sysroot/state/os/default/var");
+
+        assert_eq!(
+            path_relative_to(from, to).unwrap(),
+            PathBuf::from("../../os/default/var")
+        );
+        assert_eq!(
+            path_relative_to(&Path::new("state/deploy"), to)
+                .unwrap_err()
+                .to_string(),
+            "Paths must be absolute"
+        );
+    }
 }