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I need to set default file creation permissions for everyone to 777 [rwx], however umask uses 666 for files:

  • If I need permissions to be 444, I would issue umask 222 [666 - 222 = 444], but the problem is I need to set them to 777

How do I achieve this?

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  • @harrymc: While the question is very similar (and I was about to suggest setfacl myself), OP is asking how to make files executable by default and that is not something that default ACLs would achieve, at least not in any way I tried -- the '+x' from default ACLs is always ignored when propagating them to files.
    – grawity_u1686
    Commented Feb 14, 2021 at 12:10
  • @user1686: Executable by default exists only on Windows. The most that is possible to do is in the link I gave as duplicate. This is an unsolvable post, probably an X-Y problem, so any answer will do.
    – harrymc
    Commented Feb 14, 2021 at 13:29
  • A convoluted solution may be to use a cron job to monitor a directory every 1 min for new files, then use find to list files only, piping to xargs to change permissions [find . -type f -name '*' | xargs chmod 777]. As @harrymc mentioned, Windows is the only OS that requires execute permissions to open files, so if this is for a Windows share, use Samba and specify in the smb.conf create mask = 0777
    – JW0914
    Commented Feb 14, 2021 at 14:31
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    @JW0914: Windows doesn't require +x to open files, it requires +x to execute files -- in other words, +x on a file has the same meaning on both Windows and Linux.
    – grawity_u1686
    Commented Feb 14, 2021 at 15:29
  • @user1686 Ah, I mistyped and meant to say modify not open. Execute permission doesn't mean the same thing in Windows and Linux - to modify a file in Windows that resides in Linux w/ UGO permissions, execute is a required permission, whereas in Unix-based OSes, write is all that's required. This can be seen in Advanced Security dialogue for a file in Windows, as once Traverse folder / execute file is removed, so is Modify, and is why at least 700 is required when modifying files in a Linux Samba share from Windows (at least in Samba v3, as OpenWrt's v4 port isn't stable quite yet)
    – JW0914
    Commented Feb 14, 2021 at 15:54

1 Answer 1

Reset to default
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You really can't - there is no "default file permission" on POSIX systems.

File permissions are set when the file is created with either the open()/openat() or creat() function.

Per the open() specifications (note the bolded part, added to emphasize where file permission bits come from):

O_CREAT

If the file exists, this flag has no effect except as noted under O_EXCL below. Otherwise, if O_DIRECTORY is not set the file shall be created as a regular file; the user ID of the file shall be set to the effective user ID of the process; the group ID of the file shall be set to the group ID of the file's parent directory or to the effective group ID of the process; and the access permission bits (see <sys/stat.h>) of the file mode shall be set to the value of the argument following the oflag argument taken as type mode_t modified as follows: a bitwise AND is performed on the file-mode bits and the corresponding bits in the complement of the process' file mode creation mask. ...

The application creating the file picks the file's initial permissions, but with the bits that are non-zero in the process umask setting set to zero.

There is no "default" permission setting.

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  • This depends on the context - for example, Samba can be configured to apply default permissions on created files and/or directories in a share within the smb.conf
    – JW0914
    Commented Feb 14, 2021 at 13:56
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    @JW0914 That just means Samba is setting permissions how it wants to, and likely explicitly calling [f]chmod() after file creation to ensure permissions are set per the Samba application's settings. The operating system is not not providing those default settings.
    – Andrew Henle
    Commented Feb 14, 2021 at 14:01
  • Would a convoluted solution then be to use a cron job to monitor a directory every 1 min for new files, then use find to list files only, piping to xargs to change permissions? [find . -type f -name '*' | xargs chmod 777]
    – JW0914
    Commented Feb 14, 2021 at 14:16

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