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My Cygwin installation is behaving strangely: chmod does not work.

[09:45 Administrator@DellIns14 ~] > ls -ls /usr/bin/chmod
64K -rwxr-xr-x 1 Administrator None 38K Feb  6  2012 /usr/bin/chmod

[09:47 Administrator@DellIns14 ~] > rm /tmp/
rm: remove regular empty file `/tmp/'? y
[09:48 Administrator@DellIns14 ~] > touch /tmp/
[09:48 Administrator@DellIns14 ~] > ls -ls /tmp/
0 -rw-r--r-- 1 Administrator None 0 Jul  8 09:48 /tmp/
[09:48 Administrator@DellIns14 ~] > chmod -v +x /tmp/
mode of `/tmp/' changed from 0644 (rw-r--r--) to 0755 (rwxr-xr-x)
[09:48 Administrator@DellIns14 ~] > ls -ls /tmp/
0 -rw-r--r-- 1 Administrator None 0 Jul  8 09:48 /tmp/
[09:48 Administrator@DellIns14 ~] >

Note that the directory is writable, as the file is created.

When I look at this directory from a windows perspective, it is reported as read-only (even after I change it to read-write, it reverts to read-only).
Screen-captures are at cygwin's /tmp is read-only in windows, and cannot be changed to read-write

Can you suggest how to debug/solve?

Windows 7, Cygwin 1.7.29(0.272/5/3) i686

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I found This Answer helpful.

Besides normal POSIX permissions that contoll owner, group, other access, the file permission in Cygwin may also be affected by Windows ACL.

In your case, please try

ls -l /tmp/
getfacl /tmp/
setfacl -b /tmp/
ls -l /tmp/
chmod -v +x /tmp/
ls -l /tmp/
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If you found additional permission by getfacl, you make need to check/reset /tmp too. – Danny Zeng Feb 16 '15 at 4:03
Thanks @Danny Zeng: I'll keep the [gs]etfacl commands in mind. As for the original problem - seems that in the meantime, it vanished, and now chmod works as expected on my cygwin. Quite a few things were changed on my system in the interim, so I cannot hazard a guess what was the change that solved the problem. – boardrider Feb 17 '15 at 22:03

Kudos to this answer contents pasted below

You are probably using NTFS or FAT32 on Windows, and those filesystems do not support the executable permission. Instead, cygwin looks at the file name and contents to determine whether it's executable:

Files are considered to be executable if the filename ends with .bat, .com or .exe, or if its content starts with #!.

So you should make sure that the bash file starts with a shebang. Then, you should be able to just execute the file, disregarding the permission output of ls.

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Thanks, I'll try that. – boardrider Mar 30 at 8:01

I was unable to chmod until I found that /etc/fstab contained:

none /cygdrive cygdrive binary,noacl,posix=0,user 0 0

but needed to be:

none /cygdrive cygdrive binary,posix=0,user 0 0

After closing all open Cygwin processes and restarting, all worked.

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Thanks @rshdev, but on my machine, the noacl is already absent, viz: $ tail -1 /etc/fstab none /cygdrive cygdrive binary,posix=0,user 0 0 – boardrider 2 days ago

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