Disable generator when inst.zram is in /proc/cmdline

Closes #42.

man/zram-generator.md

@@ -20,6 +20,9 @@ The generator will be invoked by systemd early at boot. The generator will then:
 
 The generator does nothing if run inside a container (as determined by *systemd-detect-virt(8) --container*).
 
+For compatibility with Anaconda (the OS installer used by Fedora, RHEL, CentOS and other Linux distributions),
+the generator will also do nothing when `inst.zram` is present on the kernel command line.
+
 Setting the `ZRAM_GENERATOR_ROOT` environment variable makes the generator run in test mode, in which case containerisation is ignored and step `3` is skipped.<br />
 For the ramifications of `ZRAM_GENERATOR_ROOT` on config handling, see zram-generator.conf(5).
 

src/config.rs

@@ -252,6 +252,27 @@ fn get_total_memory_kb(root: &Path) -> Result<u64> {
     _get_total_memory_kb(&path)
 }
 
+fn _kernel_has_option(path: &Path, word: &str) -> Result<bool> {
+    let text = fs::read_to_string(path)?;
+
+    // The last argument wins, so check all words in turn.
+    let mut val = false;
+    for w in text.split_whitespace() {
+        if w == word || w == word.to_owned() + "=1" || w == word.to_owned() + "=on" {
+            val = true;
+        } else if w == word.to_owned() + "=0" || w == word.to_owned() + "=off" {
+            val = false;
+        }
+    }
+
+    return Ok(val);
+}
+
+pub fn kernel_has_option(root: &Path, word: &str) -> Result<bool> {
+    let path = root.join("proc/cmdline");
+    _kernel_has_option(&path, word)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -290,4 +311,35 @@ MemTotal::        8013220 kB
         file.flush().unwrap();
         _get_total_memory_kb(file.path()).unwrap();
     }
+
+    #[test]
+    fn test_kernel_has_option() {
+        let mut file = tempfile::NamedTempFile::new().unwrap();
+
+        file.write(
+            b"\
+foo=1 foo=0 foo=on foo=off foo
+",
+        )
+        .unwrap();
+        file.flush().unwrap();
+        let foo = _kernel_has_option(file.path(), "foo").unwrap();
+        assert_eq!(foo, true);
+    }
+
+    #[test]
+    fn test_kernel_has_no_option() {
+        let mut file = tempfile::NamedTempFile::new().unwrap();
+
+        file.write(
+            b"\
+foo=1
+foo=0
+",
+        )
+        .unwrap();
+        file.flush().unwrap();
+        let foo = _kernel_has_option(file.path(), "foo").unwrap();
+        assert_eq!(foo, false);
+    }
 }

src/main.rs

@@ -7,6 +7,7 @@ mod setup;
 
 use anyhow::Result;
 use clap::{crate_description, crate_name, crate_version, App, Arg};
+use log::{info, warn};
 use std::borrow::Cow;
 use std::env;
 use std::path::{Path, PathBuf};
@@ -67,6 +68,15 @@ fn main() -> Result<()> {
 
     match get_opts() {
         Opts::GenerateUnits(target) => {
+            match config::kernel_has_option(root, "inst.zram") {
+                Ok(true) => {
+                    info!("Disabled by inst.zram option in /proc/cmdline, exiting.");
+                    return Ok(());
+                }
+                Ok(false) => {}
+                Err(_) => warn!("Failed to parse /proc/cmdline, ignoring.")
+            }
+
             let devices = config::read_all_devices(&root)?;
             let output_directory = PathBuf::from(target);
             generator::run_generator(&devices, &output_directory, have_env_var)