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Diffstat (limited to 'doc/guix.texi')
| -rw-r--r-- | doc/guix.texi | 39 |
1 files changed, 30 insertions, 9 deletions
diff --git a/doc/guix.texi b/doc/guix.texi index a720f3f3bb..8d51bdf7f4 100644 --- a/doc/guix.texi +++ b/doc/guix.texi @@ -4760,14 +4760,24 @@ symlinks, as well as empty mount points for virtual file systems like procfs. @end table +@cindex relocatable binaries @item --relocatable @itemx -R Produce @dfn{relocatable binaries}---i.e., binaries that can be placed -anywhere in the file system hierarchy and run from there. For example, -if you create a pack containing Bash with: +anywhere in the file system hierarchy and run from there. + +When this option is passed once, the resulting binaries require support for +@dfn{user namespaces} in the kernel Linux; when passed +@emph{twice}@footnote{Here's a trick to memorize it: @code{-RR}, which adds +PRoot support, can be thought of as the abbreviation of ``Really +Relocatable''. Neat, isn't it?}, relocatable binaries fall to back to PRoot +if user namespaces are unavailable, and essentially work anywhere---see below +for the implications. + +For example, if you create a pack containing Bash with: @example -guix pack -R -S /mybin=bin bash +guix pack -RR -S /mybin=bin bash @end example @noindent @@ -4786,12 +4796,23 @@ In that shell, if you type @code{ls /gnu/store}, you'll notice that altogether! That is probably the simplest way to deploy Guix-built software on a non-Guix machine. -There's a gotcha though: this technique relies on the @dfn{user -namespace} feature of the kernel Linux, which allows unprivileged users -to mount or change root. Old versions of Linux did not support it, and -some GNU/Linux distributions turn it off; on these systems, programs -from the pack @emph{will fail to run}, unless they are unpacked in the -root file system. +@quotation Note +By default, relocatable binaries rely on the @dfn{user namespace} feature of +the kernel Linux, which allows unprivileged users to mount or change root. +Old versions of Linux did not support it, and some GNU/Linux distributions +turn it off. + +To produce relocatable binaries that work even in the absence of user +namespaces, pass @option{--relocatable} or @option{-R} @emph{twice}. In that +case, binaries will try user namespace support and fall back to PRoot if user +namespaces are not supported. + +The @uref{https://proot-me.github.io/, PRoot} program provides the necessary +support for file system virtualization. It achieves that by using the +@code{ptrace} system call on the running program. This approach has the +advantage to work without requiring special kernel support, but it incurs +run-time overhead every time a system call is made. +@end quotation @item --expression=@var{expr} @itemx -e @var{expr} |