Andrew Tridgell
c03c33ecef
macOS's fchmodat(..., AT_SYMLINK_NOFOLLOW) returns EPERM and applies NOTHING when the requested setgid bit is ungrantable, so "rsync -a --chmod=D2750,F0640" exits 23 and leaves the destination at 0755/0700 where 3.4.4 leaves 0750. fchmod() on an already-open descriptor does the right thing: it succeeds, drops the setgid bit it cannot grant, and applies the ordinary bits. That fd path existed but was fenced behind "#if defined __linux__". Guard it on O_NOFOLLOW so every platform that can open a leaf without following a symlink uses it, and leave the fchmodat/fchmodat2 fallbacks under __linux__. Measured on macOS with an ungrantable group: fchmodat(2750, NOFOLLOW) EPERM, 0700 -> 0700 (dir and FIFO alike) fchmod(fd, 2750) ok, 0700 -> 0750 fchmodat(0750, NOFOLLOW) ok, 0700 -> 0750 A FIFO observed by the lstat takes the pathname call instead, then one retry without S_ISGID. Opening a FIFO -- even O_NONBLOCK -- makes this process a reader for as long as the descriptor lives, which wakes a writer blocked in open(O_WRONLY) and can cost it a SIGPIPE or the bytes it writes before we close; the third line above is why that is avoidable. This does not make the function FIFO-open-free: the type comes from the lstat, so a leaf swapped to a FIFO after it is still opened, and set_file_attrs() opens FIFOs elsewhere for ACL/xattr work. Closing that needs the open constrained to the observed type, which is tracked separately. The retry is a pathname call and does not pin the inode, so a leaf swapped for another object of the same name is chmod'd instead; AT_SYMLINK_NOFOLLOW still keeps it off a symlink's target, and the held parent fd still confines the ancestors, so the out-of-tree boundary is unaffected. Only S_ISGID is retried -- clearing S_ISUID too could discard a bit that was grantable when only setgid caused the failure. Linux keeps the fd-first order it has always had. The raced-to-a-symlink refusal after openat() also accepts EMLINK and EFTYPE. ELOOP is not universal for O_NOFOLLOW on a symlink -- FreeBSD documents EMLINK and NetBSD EFTYPE -- so those two silently skipped the refusal and fell through to the (still symlink-safe) pathname call. Verified on real macOS: the regression test FAILS on93a67aa9with rc=23 and modes 0755/0700, and PASSES here with 0750/0750. (cherry picked from commit5f0f8f298e)
WHAT IS RSYNC?
Rsync is a fast and extraordinarily versatile file copying tool for both remote and local files.
Rsync uses a delta-transfer algorithm which provides a very fast method for bringing remote files into sync. It does this by sending just the differences in the files across the link, without requiring that both sets of files are present at one of the ends of the link beforehand. At first glance this may seem impossible because the calculation of diffs between two files normally requires local access to both files.
A technical report describing the rsync algorithm is included with this package.
USAGE
Basically you use rsync just like scp, but rsync has many additional options. To get a complete list of supported options type:
rsync --help
See the manpage for more detailed information.
BUILDING AND INSTALLING
If you need to build rsync yourself, check out the INSTALL page for information on what libraries and packages you can use to get the maximum features in your build.
SETUP
Rsync normally uses ssh or rsh for communication with remote systems. It does not need to be setuid and requires no special privileges for installation. You must, however, have a working ssh or rsh system. Using ssh is recommended for its security features.
Alternatively, rsync can run in `daemon' mode, listening on a socket. This is generally used for public file distribution, although authentication and access control are available.
To install rsync, first run the "configure" script. This will create a Makefile and config.h appropriate for your system. Then type "make".
Note that on some systems you will have to force configure not to use gcc because gcc may not support some features (such as 64 bit file offsets) that your system may support. Set the environment variable CC to the name of your native compiler before running configure in this case.
Once built put a copy of rsync in your search path on the local and remote systems (or use "make install"). That's it!
RSYNC DAEMONS
Rsync can also talk to "rsync daemons" which can provide anonymous or authenticated rsync. See the rsyncd.conf(5) manpage for details on how to setup an rsync daemon. See the rsync(1) manpage for info on how to connect to an rsync daemon.
WEB SITE
For more information, visit the main rsync web site.
You'll find a FAQ list, downloads, resources, HTML versions of the manpages, etc.
MAILING LISTS
There is a mailing list for the discussion of rsync and its applications that is open to anyone to join. New releases are announced on this list, and there is also an announcement-only mailing list for those that want official announcements. See the mailing-list page for full details.
BUG REPORTS
The bug-tracking web page has full details on bug reporting.
That page contains links to the current bug list, and information on how to do a good job when reporting a bug. You might also like to try searching the Internet for the error message you've received, or looking in the mailing list archives.
To send a bug report, follow the instructions on the bug-tracking page of the web site.
Alternately, email your bug report to rsync@lists.samba.org.
GIT REPOSITORY
If you want to get the very latest version of rsync direct from the source code repository, then you will need to use git. The git repo is hosted on GitHub and on Samba's site.
See the download page for full details on all the ways to grab the source.
COPYRIGHT
Rsync was originally written by Andrew Tridgell. It has been improved by many developers from around the world.
Special thanks go to Wayne Davison, who maintained rsync from 2004 to 2024.
Rsync may be used, modified and redistributed only under the terms of the GNU General Public License, found in the file COPYING in this distribution, or at the Free Software Foundation.