more common than the latter (which exists only on Linux and
FreeBSD). We don't really care about dropping the saved IDs since
there apparently is no way to quiry them in any case, so it can't
influence the build (unlike the effective IDs which are checked by
Perl for instance).
set the real uid and gid to the effective uid and gid, the Nix
binaries can be installed as owned by the Nix user and group instead
of root, so no root involvement of any kind is necessary.
Linux and FreeBSD have these functions.
users.
If the configure flag `--enable-setuid' is used, the Nix programs
nix-env, nix-store, etc. are installed with the setuid bit turned on
so that they are executed as the user and group specified by
`--with-nix-user=USER' and `--with-nix-group=GROUP', respectively
(with defaults `nix' and `nix').
The setuid programs drop all special privileges if they are executed
by a user who is not a member of the Nix group.
The setuid feature is a quick hack to enable sharing of a Nix
installation between users who trust each other. It is not
generally secure, since any user in the Nix group can modify (by
building an appropriate derivation) any object in the store, and for
instance inject trojans into binaries used by other users.
The setuid programs are owned by root, not the Nix user. This is
because on Unix normal users cannot change the real uid, only the
effective uid. Many programs don't work properly when the real uid
differs from the effective uid. For instance, Perl will turn on
taint mode. However, the setuid programs drop all root privileges
immediately, changing all uids and gids to the Nix user and group.
Nix expressions.
To subscribe to a channel (needs to be done only once):
nix-channel --add \
http://catamaran.labs.cs.uu.nl/dist/nix/channels/nixpkgs-unstable
This just adds the given URL to ~/.nix-channels (which can also be
edited manually).
To update from all channels:
nix-channel --update
This fetches the latest expressions and pulls cache manifests. The
default Nix expression (~/.nix-defexpr) is made to point to the
conjunction of the expressions downloaded from all channels.
So to update all installed derivations in the current user
environment:
nix-channel --update
nix-env --upgrade '*'
If you are really courageous, you can put this in a cronjob or
something.
You can subscribe to multiple channels. It is not entirely clear
what happens when there are name clashes between derivations from
different channels. From nix-env/main.cc it appears that the one
with the lowest (highest?) hash will be used, which is pretty
meaningless.
build logs. The program `log2xml' converts a Nix build log (read
from standard input) into XML file that can then be converted to
XHTML by the `log2html.xsl' stylesheet. The CSS stylesheet
`logfile.css' is necessary to make it look good.
This is primarily useful if the log file has a *tree structure*,
i.e., that sub-tasks such as the various phases of a build (unpack,
configure, make, etc.) or recursive invocations of Make are
represented as such. While a log file is in principle an
unstructured plain text file, builders can communicate this tree
structure to `log2xml' by using escape sequences:
- "\e[p" starts a new nesting level; the first line following the
escape code is the header;
- "\e[q" ends the current nesting level.
The generic builder in nixpkgs (not yet committed) uses this. It
shouldn't be to hard to patch GNU Make to speak this protocol.
Further improvements to the generated HTML pages are to allow
collapsing/expanding of subtrees, and to abbreviate store paths (but
to show the full path by hovering the mouse over it).
* Do not create stuff in localstatedir when doing `make install'
(since we may not have write access). In general, installation of
constant code/data should be separate from the initialisation of
mutable state.
* Fixed a segfault caused by the buffering of stderr.
* Fix now allows the specification of the full output path. This
should be used with great care, since it by-passes the normal hash
generation.
* Incremented the version number to 0.4 (prerelease).
