feat: Add unset_mode function

Used to reset the boot loader back to the previous boot loader conf

Cargo.toml

@@ -62,13 +62,14 @@ os-release = "0.1.0"
 partition-identity = "0.2.2"
 proc-mounts = "0.1.2"
 rayon = "1.0.2"
-sys-mount = "1.1.0"
+sys-mount = "1"
 tempdir = "0.3.7"
 bitflags = "1.0.4"
 err-derive = "0.1.5"
 apt-cli-wrappers = { git = "https://github.com/pop-os/apt-cli-wrappers" }
 systemd-boot-conf = "0.1.0"
 derive_more = "0.99.2"
+anyhow = "1"
 
 [dependencies.failure]
 version = "0.1.2"

ffi/distinst.vapi

@@ -1075,6 +1075,13 @@ namespace Distinst {
 
     public delegate UserAccountCreate UserAccountCallback ();
 
+    /**
+     * Attempts to unset the active mode
+     *
+     * Returns `false` on an error. See distinst logs for details on the cause of the error.
+     */
+    bool unset_mode ();
+
     int log (Distinst.LogCallback callback);
 
     [Compact]

ffi/src/lib.rs

@@ -97,6 +97,17 @@ pub unsafe extern "C" fn distinst_validate_hostname(hostname: *const libc::c_cha
 #[no_mangle]
 pub extern "C" fn distinst_minimum_disk_size(size: u64) -> u64 { distinst::minimum_disk_size(size) }
 
+#[no_mangle]
+pub extern "C" fn distinst_unset_mode() -> bool {
+    match distinst::unset_mode() {
+        Ok(()) => true,
+        Err(why) => {
+            error!("unset_mode: {:?}", why);
+            false
+        }
+    }
+}
+
 /// Log level
 #[repr(C)]
 #[derive(Copy, Clone, Debug)]

src/lib.rs

@@ -19,6 +19,7 @@ pub extern crate partition_identity;
 pub extern crate proc_mounts;
 pub extern crate sys_mount;
 
+extern crate anyhow;
 extern crate apt_cli_wrappers;
 #[macro_use]
 extern crate bitflags;
@@ -68,13 +69,18 @@ pub mod dbus_interfaces {
     pub use logind_dbus::*;
 }
 
-use external::dmlist;
 use std::{
     io::{self, Read},
     path::{Path, PathBuf},
     sync::atomic::AtomicBool,
 };
 
+use anyhow::Context;
+use external::dmlist;
+use partition_identity::PartitionID;
+use sys_mount::*;
+use systemd_boot_conf::SystemdBootConf;
+
 pub use self::{installer::*, logging::log};
 
 /// When set to true, this will stop the installation process.
@@ -123,3 +129,50 @@ pub fn minimum_disk_size(default: u64) -> u64 {
 
     casper_size + DEFAULT_ESP_SECTORS + DEFAULT_RECOVER_SECTORS + DEFAULT_SWAP_SECTORS
 }
+
+pub fn unset_mode() -> anyhow::Result<()> {
+    let mut conf = RecoveryEnv::new().context("failed to read recovery.conf")?;
+
+    if conf.get("MODE") == Some("refresh") {
+        let efi_id = conf.get("EFI_UUID").context("EFI_UUID is not set")?;
+        let prev_boot = conf.get("PREV_BOOT").context("PREV_BOOT is not set")?;
+
+        let target_dir = Path::new("target");
+
+        let _mount = mount_efi(efi_id, target_dir)?;
+
+        let mut boot_loader =
+            SystemdBootConf::new(target_dir).context("failed to open boot loader conf")?;
+
+        boot_loader.loader_conf.default = Some(prev_boot.into());
+        boot_loader.overwrite_loader_conf().context("failed to overwrite boot loader conf")?;
+
+        crate::external::remount_rw("/cdrom")
+            .context("failed to remount /cdrom with write permissions")?;
+        conf.remove("MODE");
+        conf.remove("PREV_BOOT");
+        conf.write().context("failed to write updated boot loader conf")?;
+    }
+
+    Ok(())
+}
+
+fn mount_efi(efi_id: &str, target_dir: &Path) -> anyhow::Result<UnmountDrop<Mount>> {
+    let efi_pid = if efi_id.starts_with("PARTUUID=") {
+        PartitionID::new_partuuid(efi_id[9..].to_owned())
+    } else {
+        PartitionID::new_uuid(efi_id.to_owned())
+    };
+
+    let efi_path =
+        efi_pid.get_device_path().context("failed to get device path from EFI partition")?;
+
+    if !target_dir.exists() {
+        std::fs::create_dir(target_dir)
+            .context("failed to create target directory for EFI mount")?;
+    }
+
+    Mount::new(&efi_path, target_dir, "vfat", MountFlags::empty(), None)
+        .context("failed to mount EFI partition")
+        .map(|mount| mount.into_unmount_drop(UnmountFlags::DETACH))
+}