diff options
| -rw-r--r-- | dev/todo/install-bb-without-bb.mdwn | 98 |
1 files changed, 38 insertions, 60 deletions
diff --git a/dev/todo/install-bb-without-bb.mdwn b/dev/todo/install-bb-without-bb.mdwn index 55ae48c..ca71b6b 100644 --- a/dev/todo/install-bb-without-bb.mdwn +++ b/dev/todo/install-bb-without-bb.mdwn @@ -2,11 +2,11 @@ **or, Adventures in Regressions and Crazy Ideas** -`opkg` and the Outsourced Inflation -=================================== +Two Problems +============ -The Problem ------------ +`opkg` and the Outsourced Inflation +----------------------------------- opkg-lede now [relies][opkg-lede-dd4c78a] on an external `gzip` executable. When upgrading a package, it tries to execute `gzip` to unpack maintainer @@ -17,26 +17,8 @@ package. When the package being upgraded is `busybox`, which provides `gzip`, [opkg-lede-dd4c78a]: https://git.openwrt.org/?p=project/opkg-lede.git;a=commitdiff;h=dd4c78aa88efd3b9cf516030937c684814df7962 [opkg_install_pkg]: https://git.openwrt.org/?p=project/opkg-lede.git;a=blob;f=libopkg/opkg_install.c;hb=d4ba162#l1520 -Possible Solutions ------------------- - -A wrapper script that calls `opkg-cl` (the actual binary executable) needs to -save a copy of `/bin/busybox` which `opkg-cl` can execute as `gzip`. - -**Solution 1:** `opkg-cl`'s [`gzip_exec()`][gzip_exec] is patched to execute -the absolute path of the `busybox` copy as `gzip`. - -**Solution 2:** The wrapper copies `/bin/busybox` to an empty directory and -either names the copy `gzip` or generates links to it. It then runs `opkg-cl` -with the (temporary) directory in `PATH`. - -[gzip_exec]: https://git.openwrt.org/?p=project/opkg-lede.git;a=blob;f=libbb/gzip.c;hb=d4ba162#l70 - The Amazing Alternatives of `busybox` -===================================== - -The Problem ------------ +------------------------------------- Instead of adding alternatives one at a time, [it would be nice][bb-ua] to manage all of `busybox`'s utility links using `update-alternatives`. @@ -50,40 +32,36 @@ can't be configured when first unpacked by `prokit`. [bb.pi]: http://git.proteanos.com/pkg/busybox.git/tree/busybox.pkg/postinst [u-a]: https://git.openwrt.org/?p=project/opkg-lede.git;a=blob;f=utils/update-alternatives.in;hb=d4ba162 -A Non-Solution --------------- - -`busybox`'s `postinst` script doesn't (need to) execute any commands that aren't -`ash` built-ins (`cat` is there but can be replaced with `read`), but it will -need to have its interpreter line changed from `#!/bin/sh` to -`#!/bin/busybox sh`. `update-alternatives` will need to be modified -(rewritten?) to execute `busybox` directly. - -However, there are at least two problems with this approach. - -When installing a system, `busybox` won't necessarily be the first package to be -configured. Other maintainer scripts may be executed before `busybox`'s -`postinst` is able to create the utility links they need. - -Additionally, foreign-architecture system installations aren't configured at -install time. Instead, they need to be able to at least boot far enough to run -`opkg install $(opkg list-installed | cut -d " " -f 1)`, which, again as above, -may run other maintainer scripts before `busybox`'s `postinst`. - -Another possible solution is to add special-case code to `prokit` to create -`busybox`'s links between unpacking and configuring, but that further opens the -can of worms that is compatibility between versions of `prokit` and the -distribution it installs. - -The End? --------- - -Perhaps this idea is too crazy? - -Crazier idea: could solution 2 of the first problem above actually solve this -problem? `busybox` would need to declare that it `Breaks` older versions of -`opkg-lede`, to ensure a sufficiently new `opkg-lede` is installed to handle -`busybox`'s alternatives madness. Also, the `opkg` wrapper itself would have to -be careful to execute utilities as `busybox $util` (including `#!/bin/busybox -sh`) at least until setting up the temporary directory and setting and exporting -`PATH`. +One Solution +============ + +The next version of `src:opkg-lede` (likely 0+git20190131.d4ba162-7) already +will have a [wrapper script called `opkg`][opkg] that executes `opkg-cl` (the +actual binary executable). The script can be extended to first save a copy of +`/bin/busybox` to an empty temporary directory, generate utility links to it in +the directory, and add the directory to `PATH`. Until all of this setup is +complete, the wrapper script must be careful to execute utilities as `busybox +$util` (a full path to `busybox` won't be necessary, as the usual `/bin/busybox` +will be available at that point). This includes the interpreter line, which +will need to be changed to `#!/bin/busybox sh`. `ash` built-in utilities can be +used as usual. + +The `busybox` package can't use `update-alternatives` to manage all of its +utility links until an `opkg-lede` with this wrapper script functionality is +uploaded. This is because, even if `busybox`'s `postinst` script is modified to +use the `busybox` executable directly, other packages' maintainer scripts may be +executed first, while `busybox` is unpacked but not yet configured (and +therefore utility links are not yet created). + +Once this new `opkg-lede` package is uploaded and `busybox` uses +`update-alternatives` for everything, `busybox` would need to declare that it +`Breaks` older versions of `opkg-lede`, to ensure that `opkg-lede` will preserve +a copy of the `busybox` executable and its utility links. + +The `opkg` script of the `opkg-lede` package will need to read `busybox`'s list +of alternatives links. This is currently located at +`/usr/share/busybox/alternatives`, though the file's format will change when +`busybox` uses `update-alternatives` for everything. A migration strategy for +`opkg-lede` will need to be designed. + +[opkg]: http://git.proteanos.com/pkg/opkg-lede.git/tree/opkg |