How to change all files permissions to 644 and directories to 755

Overview

There are two common task in Linux environments when handling files and folders permissions, you often will want to:

• give directories read and write privileges (drwxr-xr-x)
• give files read privileges (-rw-r–r–)

This can be done safely with find and chmod commands, taking some precautions.

$ chmod --help
Usage: chmod [OPTION]... MODE[,MODE]... FILE...
  or:  chmod [OPTION]... OCTAL-MODE FILE...
  or:  chmod [OPTION]... --reference=RFILE FILE...
Change the mode of each FILE to MODE.
With --reference, change the mode of each FILE to that of RFILE.

  -c, --changes          like verbose but report only when a change is made
  -f, --silent, --quiet  suppress most error messages
  -v, --verbose          output a diagnostic for every file processed
      --no-preserve-root  do not treat '/' specially (the default)
      --preserve-root    fail to operate recursively on '/'
      --reference=RFILE  use RFILE's mode instead of MODE values
  -R, --recursive        change files and directories recursively
      --help     display this help and exit
      --version  output version information and exit

Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.

Change directory permissions

$ find /path -type d -exec chmod 755 {} +

Change files permissions

$ find /path -type f -exec chmod 644 {} +

Run chmod efficiently

To avoid spawning one chmod process per file, we can pipe find output to xargs. This can be helpful if there are many files to process.

$ find /path -type d -print0 | xargs -0 chmod 755
$ find /path -type f -print0 | xargs -0 chmod 644

-print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs.

$ xargs --help
Usage: xargs [OPTION]... COMMAND [INITIAL-ARGS]...
Run COMMAND with arguments INITIAL-ARGS and more arguments read from input.

Mandatory and optional arguments to long options are also
mandatory or optional for the corresponding short option.
  -0, --null                   items are separated by a null, not whitespace;
                                 disables quote and backslash processing and
                                 logical EOF processing
..(truncated)

References

• Superuser answer to How to chmod all directories except files (recursively)? by nik
• StackOverflow: Using semicolon (;) vs plus (+) with exec in find