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21 Cards in this Set

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mkdir

Makes a new directory with the indicated name. Makes one directory level at a time by default.

mkdir -p

Makes a base directory and creates all sub-directories in the command. Makes it possible to create a full directory path with many levels, all from scratch.

rmdir

Removes a directory that you have access to. Only removes empty directories.




Removing directories that have content can be accomplished with the rm -r command.

rmdir -p

Removes all indicated directories in the path that exist.

chgrp

Changes the group ownership of a file or directory if you have rights to manipulate that objects ownership.




The group that you are changing to must be one that you are already a member of.

sh

Shell interpreter that will run any applications. The environment is independent of the currently logged in user shell, environment is unique, but the environment pulls parameters from the owner of the application.

chmod +s

Will change the file/application to run with the same permissions of the user that owns the file.

setuid

Run the file with the same permissions as the user that owns the file.

setgid

Run the file with the same permissions as the group that owns the file.

chmod +t

Protects files or directories from being deleted by those users/groups that do not own the files. Also known as the sticky bit permission.




Can override the normal file/directory permissions on a file.

newgrp {group name}

Will change the default group that files/folders are created under to the indicated group.

octal values

octal values are a combination of permissions for execute (x: represented by the number 1), write (w: represented by the number 2), and read (r: represented by the number 4).




So for example rwx is 7 (1+2+4=7).

umask

Will display the permissions that files and folders are created under.




Default file permissions are 666.




Default folder permissions are 777.




This command subtracts the given value numbers from the defaults.

umask octal value 0

Indicates read, write, exectute (rwx) permissions (7-0=7)

umask octal value 1

Indicates read, write (rw) permissions (7-1=6)

umask octal value 2

Indicates read, execute (rx) permissions (7-2=5)

umask octal value 3

Indicates read (r) permissions (7-3=4)

umask octal value 4

Indicates write,execute (w,x) permissions (7-4=3)

umask octal value 5

Indicates write (w) permissions (7-5=2)

umask octal value 6

Indicates execute (x) permissions (7-6=1)

umask octal value 7

Indicates no permissions (7-7=0)