From c196a5db821735b000a2e0ddc8f57623146a64d2 Mon Sep 17 00:00:00 2001 From: "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca> Date: Sun, 21 Feb 2021 15:51:32 -0500 Subject: update README --- README.rst | 36 +++++++++++++++++++++++++----------- 1 file changed, 25 insertions(+), 11 deletions(-) diff --git a/README.rst b/README.rst index d2d134f..adf5f69 100644 --- a/README.rst +++ b/README.rst @@ -2,17 +2,31 @@ tmpoverlay ========== tmpoverlay is a small, almost-POSIX shell script to create tmpfs-backed -overlayfs mounts. tmpoverlay automatically detects and uses index=on and -volatile, as well as redirect_dir and metacopy if only a single lowerdir is -used. See tmpoverlay --help for usage information. - -One important thing to note is that like any other Linux mount, an overlayfs -mount only affects new directory lookups. If a process has its current -directory or has files open inside the mount point, it continues to access the -original directory, not the overlaid one. Each process also has a cached root -directory pointer, which can only be modified by chroot (internally) or -pivot_root (globally). The pivot_root(2)_ and pivot_root(8)_ man pages should -be fully read and understood before using tmpoverlay to overmount ``/``. +overlayfs mounts. + +Features +-------- + +- minimal requirements (sh, mount, getopt, stat) + +Benefits over manually calling ``mkdir /tmp/x; mount ...`` + +- separate tmpfs allows size limit (``tmpoverlay -t size=SIZE``) +- upperdir and workdir automatically managed +- tmpfs cleanup after mount so that umount frees RAM +- synchronizes owner, permissions, and xattrs (including lowerdir ACL) +- autodetects optimization flags (redirect_dir, metacopy, index, volatile) + +Overmounting notes +------------------ + +Like any other Linux mount, an overlayfs mount only affects new directory +lookups. If a process has its current directory or has files open inside the +mount point, it continues to access the original directory, not the overlaid +one. Each process also has a cached root directory pointer, which can only be +modified by chroot (internally) or pivot_root (globally). The pivot_root(2)_ +and pivot_root(8)_ man pages should be fully read and understood before using +tmpoverlay to overmount ``/``. .. _pivot_root(2): https://man7.org/linux/man-pages/man2/pivot_root.2.html .. _pivot_root(8): https://man7.org/linux/man-pages/man8/pivot_root.8.html -- cgit v1.2.3-70-g09d2