You must also specify a server and a base DN (distinguished name) with -ldapserver= and -ldapbasedn=. To use this option, you must install the nss-pam-ldapd package. enableldap - Turns on LDAP support in /etc/nf, allowing your system to retrieve information about users (for example, their UIDs, home directories, and shells) from an LDAP directory. useshadow or -enableshadow - Use shadow passwords. nisserver= - Server to use for NIS services (broadcasts by default). nisdomain= - NIS domain name to use for NIS services. A domain should almost always be set by hand with the -nisdomain= option. By default, -enablenis uses whatever domain it finds on the network. The only information they can gain from the file is its name and attributes.-enablenis - Turns on NIS support. Together, both features prevent other users from altering or replacing any file you have in a public directory. The sticky bit, together with the default umask of 077, solves a big problem for less secure systems. Unlike with file sticky bits, the sticky bit on directories remains there until the directory owner or superuser explicitly removes the directory or changes the permissions. All PUBLIC directories should be configured with sticky bit. Only the file owner and the superuser can remove files from that directory. The Sticky bit ( t) will prevent users from altering or replacing any other user's files. To enable Posix ACLs, install the acl packageĭocumentation can then be found in the man pages for acl, setfacl, getfacl Sticky Bit Posix ACLs are a way of achieving a finer granularity of permissions than is possible with the standard Unix file permissions. $ sudo chown tux:mygroup file1.txt ACLs - Access control lists Changing Ownership and Group membershipĪ file's owner can be changed using the chown command.Ī file's group can be changed using the chgrp or chown command.Ĭhown can also change the owner and group in a single command: $ sudo find /path/to/Dir -type d -print0 | xargs -0 sudo chmod 755Īgain if using sudo be careful, in particular watch for extra spaces in your command/path. $ sudo find /path/to/Dir -type f -print0 | xargs -0 sudo chmod 644 To assign reasonably secure permissions to files and folders/directories, it's common to give files a permission of 644, and directories a 755 permission, using the find command and a pipe we can target just files or just folders as in the following examples. $ sudo chmod o+x /usr/local/bin/somefile Recursive Permission ChangesĬhmod -R will change all the permissions of each file and folder under a specified directory at once. Note that changing permissions incorrectly can quickly make your system unusable! Please be careful when using sudo! To change or edit files that are owned by root, sudo chmod must be used. Changing these permissions can create security problems. Some files are configured to have very restrictive permissions to prevent unauthorized access. Using letters is easier to understand for most people. There are two ways to modify permissions, with numbers or with letters. The command to modify permissions is chmod. In the example above the Group permission is r- so members of the group will have Read permission but not Write or Execute permission to file1.txt User These rights are shown three times, first for the Owner, then the Group and lastly Others (world) The letters rwx stand for Read/ Write/E xecute permission. rwxr-rw- 1 user user 0 Jan 19 12:59 file1.txt The ouptut of ls -l will show the current permissions for files and folders: Linux/unix system permissions allow or prevent other users from viewing, modifying or executing any particular file.
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