Use ls -l to see the permissions of files (list-long). They will appear like this, note that I have added spaces between permissions to make it easier to read: Show Where: r = read, w = write, x = execute - rwx rw- r-- 1 newuser newuser typeownergroupothers The two names at the end are the username and group respectively. chmod Change file access permissions for a file(s). There are two methods to change permissions using chmod; letters or numbers. Letters Method: use a + or - (plus or minus sign) to add or remove permissions for a file respectively. Use an equals sign =, to specify new permissions and remove the old ones for the particular type of user(s). You can use chmod letter where the letters are: a (all (everyone)), u (user), g (group) and o (other). Examples: chmod u+rw somefile This would give the user read and write permission. chmod o-rwx somefile This will remove read/write/execute permissions from other users (doesn't include users within your group). chmod a+r somefile This will give everyone read permission for the file. chmod a=rx somefile This would give everyone execute and read permission to the file, if anyone had write permission it would be removed. Numbers Method: you can also use numbers (instead of letters) to change file permissions. Where: r (read) = 4 w (write) = 2 x (execute) = 1 Numbers can be added together so you can specify read/write/execute permissions; read+write = 6, read+execute = 5, read+write+execute = 7 Examples: chmod 777 somefile This would give everyone read/write/execute permission on “this_file”. The first number is user, second is group and third is everyone else (other). chmod 521 somefile This would give the user read and execute permission, and the group write permission (but not read permission!) and everyone else execute permission. (Note that it's just an example, settings like that don't really make sense...). chownChanges the ownership rights of a file (hence the name 'chown' - change owner). This program can only be used by root. Use the -R option to change things recursively, in other words, all matching files including those in subdirectories. Command syntax: chown owner:group the_file_namesticky bit Only the person who created the file within a directory may delete it, even if other people have write permission. You can turn it on by typing: chmod 1700 somedirectory (where 1 = sticky bit) or (where t represents the sticky bit) chmod +t somedirectory To turn it off you would need to type: chmod 0700 somefile (where the zero would mean no sticky bit) or (where t represents the sticky bit) chmod -t somefile Note that the permissions aren't relevant in the numbers example, only the first number (1 = on, 0 = off). An example of a sticky directory is usually /tmp suidAllow SUID/SGID (switch user ID/switch group ID) access. You would normally use chmod to turn this on or off for a particular file, suid is generally considered a security hazard so be careful when using this. Example: chmod u+s file_name This will give everyone permission to execute the file with the permissions of the user who set the +s switch.
chattr Change file system attributes (works on ext2fs and possibly others...). Use the -R option to change files recursively, chattr has a large number of attributes which can be set on a file, read the manual page for further information. Example: chattr +i /sbin/lilo.conf[1] This sets the 'immutable' flag on a file. Use a '+' to add attributes and a '-' to take them away. The +i will prevent any changes (accidental or otherwise) to the “lilo.conf” file. If you wish to modify the lilo.conf file you will need to unset the immutable flag: chattr -i. Note some flags can only be used by root; -i, -a and probably many others. Note there are many different attributes that chattr can change, here are a few more which may be useful:
(list attributes). This will list if whether a file has any special attributes (as set by chattr). Use the -R option to list recursively and try using the -d option to list directories like other files rather than listing their contents. Command syntax: lsattr This will list files in the current directory, you may also like to specify a directory or a file: lsattr /directory/or/file Which command is used to assign read/write permission to owner?The format of the chmod command is chmod [permission] [filename]. The permission can be specified in either the symbolic or absolute mode. In the symbolic mode you must specify three things. One, who to change the permission for; owner (u), group (g) and/or world (o).
What is the command to set the execute permissions to all the files?To modify the permission flags on existing files and directories, use the chmod command ("change mode"). It can be used for individual files or it can be run recursively with the -R option to change permissions for all of the subdirectories and files within a directory.
Which command is used to apply permission to a file?The chmod command enables you to change the permissions on a file. You must be superuser or the owner of a file or directory to change its permissions.
What is the use of chmod 777?The command chmod -R 777 / makes every single file on the system under / (root) have rwxrwxrwx permissions. This is equivalent to allowing ALL users read/write/execute permissions.
|