This patch allows to build distinct binaries for specific btrfs subcommands, e.g. "btrfs-subvolume-show" which would be identical to "btrfs subvolume show".
Motivation: While btrfs-progs offer the all-inclusive "btrfs" command, it gets pretty cumbersome to restrict privileges to the subcommands [1]. Common approaches are to either setuid root for "/sbin/btrfs" (which is not recommended at all), or to write sudo rules for each subcommand. Separating the subcommands into distinct binaries makes it easy to set elevated privileges using capabilities(7) or setuid. A typical use case where this is needed is when it comes to automated scripts, e.g. btrbk [2] [3] creating snapshots and send/receive them via ssh. Description: Patch 1 adds a template as well as a generator shell script for the splitted subcommands. Patch 2 adds the generated subcommand source files. Patch 3-5 adds a "install-splitcmd-setcap" make target, with different approaches (either hardcoded in Makefile, or more generically by including "Makefile.install_setcap" generated by "splitcmd-gen.sh"). Open Questions: 1. "make install-splitcmd-setcap" installs the binaries with hardcoded group "btrfs". This needs to be configurable (how?). Another approach would be to not set the group at all, and leave this to the user or distro packaging script. 2. Instead of the "install-splitcmd-setcap" make target, we could introduce a "configure --enable-splitted-subcommands" option, which would simply add all splitcmd binaries to the "all" and "install" targets without special treatment, and leave the setcap stuff to the user or distro packaging script (at least in gentoo, this needs to be specified using the "fcaps" eclass anyways [5]). References: [1] https://www.spinics.net/lists/linux-btrfs/msg75736.html [2] https://github.com/digint/btrbk [3] https://github.com/digint/btrfs-progs-btrbk [4] https://github.com/digint/btrfs-progs/tree/splitcmd-setcap [5] https://dev.tty0.ch/portage/digint-overlay.git (sys-fs/btrfs-progs-btrbk) Axel Burri (6): btrfs-progs: splitcmd-gen.sh: create btrfs-<subcommand> binaries for selected subcommands btrfs-progs: add btrfs-<subcommand> source files generated by splitcmd-gen.sh btrfs-progs: Makefile: add "install-splitcmd-setcap" target, installs splitcmd binaries with appropriate capabilities btrfs-progs: Makefile: include Makefile.install_setcap generated by splitcmd-gen.sh btrfs-progs: Makefile: move progs_splitcmd variable to Makefile.install_setcap btrfs-progs: add splitcmd binaries to gitignore .gitignore | 9 +++++ Makefile | 20 +++++++++++ Makefile.inc.in | 1 + Makefile.install_setcap | 12 +++++++ btrfs-filesystem-usage.c | 23 +++++++++++++ btrfs-qgroup-destroy.c | 23 +++++++++++++ btrfs-receive.c | 23 +++++++++++++ btrfs-send.c | 23 +++++++++++++ btrfs-subvolume-delete.c | 23 +++++++++++++ btrfs-subvolume-list.c | 23 +++++++++++++ btrfs-subvolume-show.c | 23 +++++++++++++ btrfs-subvolume-snapshot.c | 23 +++++++++++++ configure.ac | 1 + splitcmd-gen.sh | 86 ++++++++++++++++++++++++++++++++++++++++++++++ splitcmd.c.in | 17 +++++++++ 15 files changed, 330 insertions(+) create mode 100644 Makefile.install_setcap create mode 100644 btrfs-filesystem-usage.c create mode 100644 btrfs-qgroup-destroy.c create mode 100644 btrfs-receive.c create mode 100644 btrfs-send.c create mode 100644 btrfs-subvolume-delete.c create mode 100644 btrfs-subvolume-list.c create mode 100644 btrfs-subvolume-show.c create mode 100644 btrfs-subvolume-snapshot.c create mode 100755 splitcmd-gen.sh create mode 100644 splitcmd.c.in -- 2.16.4
