faster than the old mode when fsyncs are enabled, because it only
performs an fsync() when doing a checkpoint, rather than at every
commit. Some timings for doing a "nix-instantiate /etc/nixos/nixos
-A system" after modifying the stdenv setup script:
42.5s - SQLite 3.6.23 with truncate mode and fsync
3.4s - SQLite 3.6.23 with truncate mode and no fsync
32.1s - SQLite 3.7.0 with truncate mode and fsync
16.8s - SQLite 3.7.0 with WAL mode and fsync, auto-checkpoint
every 1000 pages
8.3s - SQLite 3.7.0 with WAL mode and fsync, auto-checkpoint
every 8192 pages
1.7s - SQLite 3.7.0 with WAL mode and no fsync
The default is now to use WAL mode with fsyncs. Because WAL doesn't
work on remote filesystems such as NFS (as it uses shared memory),
truncate mode can be re-enabled by setting the "use-sqlite-wal"
option to false.
Defining -D_FILE_OFFSET_BITS=64 works on most platforms, but not on all (i.e.
Solaris). Also, the Autoconf macro offers the user a switch to disable the
functionality in case of problems.
would just silently store only (fileSize % 2^32) bytes.
* Use posix_fallocate if available when unpacking archives.
* Provide a better error message when trying to unpack something that
isn't a NAR archive.
bind-mounts we do are only visible to the builder process and its
children. So accidentally doing "rm -rf" on the chroot directory
won't wipe out /nix/store and other bind-mounted directories
anymore. Also, the bind-mounts in the private namespace disappear
automatically when the builder exits.
get the basename of the channel URL (e.g., nixpkgs-unstable). The
top-level Nix expression of the channel is now an attribute set, the
attributes of which are the individual channels (e.g.,
{nixpkgs_unstable = ...; strategoxt_unstable = ...}). This makes
attribute paths ("nix-env -qaA" and "nix-env -iA") more sensible,
e.g., "nix-env -iA nixpkgs_unstable.subversion".
that have to be done as root: running builders under different uids,
changing ownership of build results, and deleting paths in the store
with the wrong ownership).
* Some refactoring: put the NAR archive integer/string serialisation
code in a separate file so it can be reused by the worker protocol
implementation.
Rather, setuid support is now always compiled in (at least on
platforms that have the setresuid system call, e.g., Linux and
FreeBSD), but it must enabled by chowning/chmodding the Nix
binaries.
externals directory. This is in particular useful because though
most systems have bzip2/bunzip2, they don't always have libbz2,
which we need for bsdiff/bspatch.
implementations of MD5, SHA-1 and SHA-256. The main benefit is that
we get assembler-optimised implementations of MD5 and SHA-1 (though
not SHA-256 (at least on x86), unfortunately). OpenSSL's SHA-1
implementation on Intel is twice as fast as ours.
http://www.daemonology.net/bsdiff/bsdiff-4.2.tar.gz) into the source
tree. The license is a bit peculiar, but it does allow verbatim
copying, which is what we do here (i.e., so don't make any changes
to the sources).
Previously there was the problem that all files read by nix-env
etc. should be reachable and readable by the Nix user. So for
instance building a Nix expression in your home directory meant that
the home directory should have at least g+x or o+x permission so
that the Nix user could reach the Nix expression. Now we just
switch back to the original user just prior to reading sources and
the like. The places where this happens are somewhat arbitrary,
however. Any scope that has a live SwitchToOriginalUser object in
it is executed as the original user.
* Back out r1385. setreuid() sets the saved uid to the new
real/effective uid, which prevents us from switching back to the
original uid. setresuid() doesn't have this problem (although the
manpage has a bug: specifying -1 for the saved uid doesn't leave it
unchanged; an explicit value must be specified).
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.
