How to Configure ACL in Linux FileSystem

<div dir="ltr" style="text-align: left;" trbidi="on"> <h2 class="title single-title title20" style="background-color: white; border: 0px; font-family: 'Roboto Slab'; font-size: 28px; line-height: 38px; margin: 0px 0px 5px; opacity: 1; outline: 0px; padding: 0px; transition: opacity 0.24s ease-in-out; vertical-align: baseline; visibility: visible;"> <span style="color: #990000;"><u><i>Configure ACL in Linux FileSystem</i></u></span></h2> <div> <div style="background-color: white; border: 0px; font-size: 16px; line-height: 28px; margin-bottom: 20px; outline: 0px; padding: 0px; vertical-align: baseline;"> <span style="font-family: "georgia" , "times new roman" , serif;"><span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-size: inherit; font-weight: 700; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Ext3</span> and <span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-size: inherit; font-weight: 700; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Ext4</span> filesystem includes support of ACLs on files and directories. ACL provides more control permissions on file than standard three access categories (owner, group and other ). Using ACL you can provide permission to specific user or group to file.<br /></span></div> <div style="background-color: white; border: 0px; font-size: 16px; line-height: 28px; margin-bottom: 20px; outline: 0px; padding: 0px; vertical-align: baseline;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8PIUgbEhY7YRkoZkY_ycfUsaC1iFBDlfTI2RPseUTTGJFwqo_RxDQOGRx-81DG42DgZeHzXtC9PcieWNIbyVz53baCPbuyUP0WPC7WZ7rrW5NlG23aHC8o474ZV_Qau4j-mRYNWvZyhBg/s1600/acls_map_ext_www.hackthesec.co.in.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="108" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8PIUgbEhY7YRkoZkY_ycfUsaC1iFBDlfTI2RPseUTTGJFwqo_RxDQOGRx-81DG42DgZeHzXtC9PcieWNIbyVz53baCPbuyUP0WPC7WZ7rrW5NlG23aHC8o474ZV_Qau4j-mRYNWvZyhBg/s320/acls_map_ext_www.hackthesec.co.in.png" width="320" /></a><span style="font-family: "georgia" , "times new roman" , serif;">Before working on <b>ACL </b>make sure that <b>ACL </b>is enabled on <b>mounted </b>file system. You can enable it during mounting filesystem with ACL option.</span></div> <div style="background-color: white; border: 0px; font-size: 16px; line-height: 28px; margin-bottom: 20px; outline: 0px; padding: 0px; vertical-align: baseline;"> <span style="font-family: "georgia" , "times new roman" , serif;">Use following command Check if ACL is enabled on filesystem or not.</span></div> <pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;"># </span><span style="color: lime;">mount</span><span style="color: white;"> /dev/mapper/VolGroup00-LogVol00 on / type ext3 (</span><span style="color: lime;">rw,noatime,<span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-weight: 700; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">acl</span></span><span style="color: white;">)</span></span><span style="color: white; font-size: 0.9em;"> </span></pre> <div style="background-color: white; border: 0px; font-size: 16px; line-height: 28px; margin-bottom: 20px; outline: 0px; padding: 0px; vertical-align: baseline;"> <span style="font-family: "georgia" , "times new roman" , serif;">Enable ACL by remounting file system using following command.</span></div> <pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="color: lime; font-family: "courier new" , "courier" , monospace; font-size: large;"># mount -o remount,acl / </span></pre> <div style="background-color: white; border: 0px; font-size: 16px; line-height: 28px; margin-bottom: 20px; outline: 0px; padding: 0px; vertical-align: baseline;"> <span style="font-family: "georgia" , "times new roman" , serif;">To enable ACL default on system bootup update following entry in <span style="color: #990000;">/etc/fstab</span> file.</span></div> <pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;">/dev/VolGroup00/LogVol00 / ext3 defaults,</span><span style="color: lime;"><orange>acl</orange> </span><span style="color: white;">1 1 </span></span></pre> <h4 class="heading1" style="background-color: white; border: 0px; font-family: 'Roboto Slab'; font-size: 24px; font-weight: bolder; line-height: 34px; margin: 45px 0px 12px; opacity: 1; outline: 0px; padding: 0px; transition: opacity 0.24s ease-in-out; vertical-align: baseline; visibility: visible;"> <span style="color: #0b5394;">Configure ACL on File</span></h4> <div style="background-color: white; border: 0px; font-size: 16px; line-height: 28px; margin-bottom: 20px; outline: 0px; padding: 0px; vertical-align: baseline;"> <span style="font-family: "georgia" , "times new roman" , serif;">If we want that user Bob to have all permissions on a file. Use following command.</span></div> <pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;"># setfacl -m u:Bob:rwx </span><span style="color: lime;">hackthesec.txt</span><span style="color: white;"> </span></span></pre> <div style="background-color: white; border: 0px; font-size: 16px; line-height: 28px; margin-bottom: 20px; outline: 0px; padding: 0px; vertical-align: baseline;"> <span style="font-family: "georgia" , "times new roman" , serif;">Details of parameters:</span></div> <pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: lime;">setfacel</span><span style="color: white;">: is a command itself -m : is used to modify ACL. u : it denotes to assign permission to a user bob : a system user </span><span style="color: lime;">rwx : file permissions. </span><span style="color: white;">hackthesec.txt: file on which bob will get access.</span></span><span style="color: white; font-size: 0.9em;"> </span></pre> <h4 class="heading1" style="background-color: white; border: 0px; font-family: 'Roboto Slab'; font-size: 24px; font-weight: bolder; line-height: 34px; margin: 45px 0px 12px; opacity: 1; outline: 0px; padding: 0px; transition: opacity 0.24s ease-in-out; vertical-align: baseline; visibility: visible;"> <span style="color: #0b5394;">Check ACL on File</span></h4> <div style="background-color: white; border: 0px; font-size: 16px; line-height: 28px; margin-bottom: 20px; outline: 0px; padding: 0px; vertical-align: baseline;"> <span style="font-family: "georgia" , "times new roman" , serif;">Use following command to check ACL configured on a file.</span></div> <pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;"># </span><span style="color: lime;">getfacl</span><span style="color: white;"> hackthesec.txt </span></span></pre> <div style="background-color: white; border: 0px; font-size: 16px; line-height: 28px; margin-bottom: 20px; outline: 0px; padding: 0px; vertical-align: baseline;"> <span style="font-family: "georgia" , "times new roman" , serif;">Output:</span></div> <pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;"># file: hackthesec.txt # owner: root # group: root user::rw- </span><span style="color: lime;"><span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-weight: 700; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">user:Bob:rwx</span> </span><span style="color: white;">group::r-- mask::rwx other::r--</span></span><span style="color: white; font-size: 0.9em;"> </span></pre> <h4 class="heading1" style="background-color: white; border: 0px; font-family: 'Roboto Slab'; font-size: 24px; font-weight: bolder; line-height: 34px; margin: 45px 0px 12px; opacity: 1; outline: 0px; padding: 0px; transition: opacity 0.24s ease-in-out; vertical-align: baseline; visibility: visible;"> <span style="color: #0b5394;">Remove ACL from File</span></h4> <div style="background-color: white; border: 0px; font-size: 16px; line-height: 28px; margin-bottom: 20px; outline: 0px; padding: 0px; vertical-align: baseline;"> <span style="font-family: "georgia" , "times new roman" , serif;">If we don’t need the ACL in file, we can simply remove using following command.</span></div> <pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;"># </span><span style="color: lime;">setfacl -x u:Bob</span><span style="color: white;"> hackthesec.txt HackTheSec <a href="https://www.twitter.com/hackthesecurity" target="_blank">HackTheSec-Twitter</a> <a href="http://www.hackthesec.co.in/">www.hackthesec.co.in</a></span></span></pre> </div> </div>

How to Configure ACL in Linux FileSystem

Configure ACL in Linux FileSystem Ext3 and Ext4 filesystem includes support of ACLs on files and directories. ACL provides more control permissions on file than standard three access categories (owne…

Read more »