On Tue, Apr 29, 2025 at 02:57:13PM +0200, Ján Tomko wrote: > On a Tuesday in 2025, Daniel P. Berrangé via Devel wrote: > > Over the years we've made various changes to stop hardcoding paths at > > build time, but the work is incomplete. > > > > This bit us significantly in Fedora 42 where they have merged the 'sbin' > > and 'bin' dirs together. In the build environment we have a clean > > install where '/sbin' and '/usr/sbin' are simply symlinks to '/usr/bin'. > > > > Our meson.build logic preferentially looks in '/sbin' and '/usr/sbin' > > to find programs, and thus it finds *all* binaries in '/sbin' and then > > hardcodes this path. This happens even for binaries that have always > > been in '/usr/bin' and NEVER '/sbin' or '/usr/sbin' > > > > On fresh Fedora installs this is fine as the symlinks match the build > > environment. > > > > On upgraded Fedora installs, however, '/sbin' and '/usr/sbin' remain > > separate directories and inside they symlink individual binaries, > > if-and-only-if the binary was in '/sbin' in Fedora 41. > > > > Thus many of the binaries we found in /sbin don't actually exist and > > libvirt thus breaks. > > > > There is really no reason why we should be harcoding any paths at > > build time. virCommand happily uses virFindFileInPath for any paths > > which are not already absolute. $PATH includes '/sbin' and '/usr/sbin' > > when we're running privileged, and when unprivileged we shouldn't need > > to run binaries from there. > > > > Does anyone happen to remember the original reason? > > The only thing I can think of is saving the lookup time, but that has to > be negligible compared to the cost of fork and the command actually > doing something
I've not checked, but I expect that a very very very long time ago virCommand would not lookup binaries in $PATH, and then we just cargo-culted the configure.ac checks, later meson.build checks, without thinking about it more. Yes, we've got the cost of a few stat() calls, but as you say, it isn't worth worrying about that in the context of a heavy fork+exec. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
