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Add a systemd generator to fixup Anaconda's /etc/fstab
This is a giant and hacky workaround for ostreedev/ostree#3193 The better real fix is probably in either systemd or anaconda (more realistically both) but let's paper over things here for now. Having code to run as a generator will likely be useful in the future anyways. Signed-off-by: Colin Walters <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,114 @@ | ||
| use std::io::BufRead; | ||
|
|
||
| use anyhow::{Context, Result}; | ||
| use cap_std::fs::Dir; | ||
| use cap_std_ext::{cap_std, dirext::CapStdExtDirExt}; | ||
| use fn_error_context::context; | ||
| use rustix::{fd::AsFd, fs::StatVfsMountFlags}; | ||
|
|
||
| const FSTAB_ANACONDA_STAMP: &str = "Created by anaconda"; | ||
|
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| /// Called when the root is read-only composefs to reconcile /etc/fstab | ||
| #[context("bootc generator")] | ||
| pub(crate) fn fstab_generator_impl(root: &Dir, unit_dir: &Dir) -> Result<()> { | ||
| // Do nothing if not ostree-booted | ||
| if !root.try_exists("run/ostree-booted")? { | ||
| return Ok(()); | ||
| } | ||
|
|
||
| if let Some(fd) = root | ||
| .open_optional("etc/fstab") | ||
| .context("Opening /etc/fstab")? | ||
| .map(std::io::BufReader::new) | ||
| { | ||
| let mut from_anaconda = false; | ||
| // Only read 10 lines just because it should be near the start | ||
| for line in fd.lines().take(10) { | ||
| let line = line.context("Reading /etc/fstab")?; | ||
| if line.contains(FSTAB_ANACONDA_STAMP) { | ||
| from_anaconda = true; | ||
| break; | ||
| } | ||
| } | ||
| tracing::debug!("/etc/fstab from anaconda: {from_anaconda}"); | ||
| if from_anaconda { | ||
| generate_fstab_editor(unit_dir)?; | ||
| } | ||
| } | ||
| Ok(()) | ||
| } | ||
|
|
||
| /// Main entrypoint for the generator | ||
| pub(crate) fn generator(root: &Dir, unit_dir: &Dir) -> Result<()> { | ||
| // Right now we only do something if the root is a read-only overlayfs (a composefs really) | ||
| let st = rustix::fs::fstatfs(root.as_fd())?; | ||
| if st.f_type != libc::OVERLAYFS_SUPER_MAGIC { | ||
| tracing::trace!("Root is not overlayfs"); | ||
| return Ok(()); | ||
| } | ||
| let st = rustix::fs::fstatvfs(root.as_fd())?; | ||
| if !st.f_flag.contains(StatVfsMountFlags::RDONLY) { | ||
| tracing::trace!("Root is writable"); | ||
| return Ok(()); | ||
| } | ||
| fstab_generator_impl(root, unit_dir) | ||
| } | ||
|
|
||
| /// Parse /etc/fstab and check if the root mount is out of sync with the composefs | ||
| /// state, and if so, fix it. | ||
| fn generate_fstab_editor(unit_dir: &Dir) -> Result<()> { | ||
| let unit = "bootc-fstab-edit.service"; | ||
| unit_dir.atomic_write( | ||
| unit, | ||
| "[Unit]\n\ | ||
| Before=local-fs-pre.target\n\ | ||
| [Service]\n\ | ||
| ExecStart=bootc internals fixup-etc-fstab | ||
| ", | ||
| )?; | ||
| let target = "local-fs-pre.target.wants"; | ||
| unit_dir.create_dir_all(target)?; | ||
| unit_dir.symlink(&format!("../{unit}"), &format!("{target}/{unit}"))?; | ||
| Ok(()) | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| fn fixture() -> Result<cap_std_ext::cap_tempfile::TempDir> { | ||
| let tempdir = cap_std_ext::cap_tempfile::tempdir(cap_std::ambient_authority())?; | ||
| tempdir.create_dir("etc")?; | ||
| tempdir.create_dir("run")?; | ||
| tempdir.create_dir_all("run/systemd/system")?; | ||
| Ok(tempdir) | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_generator_no_fstab() -> Result<()> { | ||
| let tempdir = fixture()?; | ||
| let unit_dir = &tempdir.open_dir("run/systemd/system")?; | ||
| fstab_generator_impl(&tempdir, &unit_dir).unwrap(); | ||
|
|
||
| assert_eq!(unit_dir.entries()?.count(), 0); | ||
| Ok(()) | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_generator_fstab() -> Result<()> { | ||
| let tempdir = fixture()?; | ||
| let unit_dir = &tempdir.open_dir("run/systemd/system")?; | ||
| // Should still be a no-op | ||
| tempdir.atomic_write("etc/fstab", "# Some dummy fstab")?; | ||
| fstab_generator_impl(&tempdir, &unit_dir).unwrap(); | ||
| assert_eq!(unit_dir.entries()?.count(), 0); | ||
|
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| // Also a no-op, not booted via ostree | ||
| tempdir.atomic_write("etc/fstab", &format!("# {FSTAB_ANACONDA_STAMP}"))?; | ||
| fstab_generator_impl(&tempdir, &unit_dir).unwrap(); | ||
| assert_eq!(unit_dir.entries()?.count(), 0); | ||
|
|
||
| // Now it should generate | ||
| tempdir.atomic_write("run/ostree-booted", "ostree booted")?; | ||
| fstab_generator_impl(&tempdir, &unit_dir).unwrap(); | ||
| assert_eq!(unit_dir.entries()?.count(), 1); | ||
|
|
||
| Ok(()) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1 @@ | ||
| pub(crate) mod generator; |