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<h2 id="in-linux-systems-chattr-and-lsattr">In Linux systems (chattr and lsattr)</h2> <h3>File system support</h3> <p>The command line tools chattr (to manipulate attributes) and lsattr (to list attributes) were originally specific to the Second Extended Filesystem family (<a href="/facts/Ext2/ftyVw4Kv">ext2</a>, <a href="/facts/Ext3/VSEhX1WQ">ext3</a>, <a href="/facts/Ext4/zFbQRpsh">ext4</a>), and are available as part of the <a href="/facts/E2fsprogs/nlytEvMn">e2fsprogs</a> package. </p><p>However, the functionality has since been extended, fully or partially, to many other systems, including <a href="/facts/XFS/2I4Wn5wG">XFS</a>, <a href="/facts/ReiserFS/aGg9PTtk">ReiserFS</a>, <a href="/facts/JFS_(file_system)/bmJLqaP8">JFS</a> and <a href="/facts/OCFS2/Hh7UcTvl">OCFS2</a>. The btrfs file system includes the attribute functionality, including the C flag, which turns off the built-in copy-on-write (CoW) feature of btrfs due to slower performance associated with CoW. </p> <h3>chattr description</h3> <p>The form of the chattr command is: </p> chattr [-RVf] [-+=AacDdijsTtSu] [-v version] files... <ul><li>-R recursively changes attributes of directories and their contents</li> <li>-V is to be verbose and print the program version</li> <li>-f suppresses most error messages</li></ul> <h3>lsattr description</h3> <p>The form of the lsattr command (gnu 1.41.3): </p> lsattr [ -RVadv ] [ files... ] <ul><li>-R recursively lists attributes of directories and their contents</li> <li>-V displays the program version</li> <li>-a lists all files in directories, including <a href="/facts/Hidden_file_and_hidden_directory/5hXmMbGP">dotfiles</a></li> <li>-d lists directories like other files, rather than listing their contents</li></ul> <h3>Attributes</h3> <p>Some attributes include: </p> File attributes on a Linux file system according to the chattr(1) Linux man page<table><tbody><tr><th>Attribute</th><th>lsattr flag</th><th>chattr option</th><th>Semantics and rationale</th></tr><tr><th>No atime updates</th><td>A</td><td>+A to set-A to clear</td><td><ul><li>When a file with the A attribute set is accessed, its <a href="/facts/Stat_(Unix)/5DeWQJFS">atime record</a> is not modified.</li><li>This avoids a certain amount of disk I/O operations.</li></ul></td></tr><tr><th>Append only</th><td>a</td><td>+a to set-a to clear<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a></td><td><ul><li>A file with the a attribute set can only be open in append mode for writing.</li></ul></td></tr><tr><th>Compressed</th><td>c</td><td>+c to set-c to clear<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a></td><td><ul><li>A file with the c attribute set is automatically compressed on the disk by the kernel.</li><li>A read from this file returns uncompressed data.</li><li>A write to this file compresses data before storing them on the disk.</li></ul></td></tr><tr><th>No Copy-on-Write (CoW)</th><td>C</td><td>+C to set-C to clear<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a></td><td><ul><li>A file with the C attribute will not be subject to Copy-on-Write updates.</li><li>Updates to these files may not be subject to atomic snapshots, and may lack some reliability information on some filesystems and kernels.</li></ul></td></tr><tr><th>Synchronous directory updates</th><td>D</td><td>+D to set-D to clear</td><td><ul><li>When a directory with the D attribute set is modified, the changes are written synchronously on the disk</li><li>This is equivalent to the dirsync <a href="/facts/Mount_(Unix)/VlDPf1Hm">mount option</a>, applied to a subset of the files.</li></ul></td></tr><tr><th>No dump</th><td>d</td><td>+d to set-d to clear</td><td><ul><li>A file with the d attribute set is not candidate for backup when the <a href="/facts/Dump_(Unix)/0GhPTYJj">dump program</a> is run.</li></ul></td></tr><tr><th>Compression error</th><td>E</td><td><i>(unavailable)</i></td><td><ul><li>The E attribute is used by the experimental compression patches to indicate that a compressed file has a compression error.</li></ul></td></tr><tr><th>Extent format</th><td>e</td><td><i>(unavailable)</i></td><td><ul><li>The e attribute indicates that the file is using <a href="/facts/Extent_(file_systems)/lpCqWR4r">extents</a> for mapping the blocks on disk.</li></ul></td></tr><tr><th>Huge file</th><td>h</td><td><i>(unavailable)</i></td><td><ul><li>The h attribute indicates the file is storing its blocks in units of the filesystem blocksize instead of in units of sectors.</li><li>It means that the file is, or at one time was, larger than 2TB.</li></ul></td></tr><tr><th>Indexed directory</th><td>I</td><td><i>(unavailable)</i></td><td><ul><li>The I attribute is used by the <a href="/facts/HTree/GErqFAGE">htree program</a> code to indicate that a directory is being indexed using hashed trees.</li></ul></td></tr><tr><th>Immutable</th><td>i</td><td>+i to set-i to clear<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a></td><td><ul><li>A file with the i attribute cannot be modified.</li><li>It cannot be deleted or renamed, no link can be created to this file and no data can be written to the file.</li><li>When set, prevents, <i>even the superuser</i>, from erasing or changing the contents of the file.</li></ul></td></tr><tr><th>Data journaling</th><td>j</td><td>+j to set-j to clear<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a></td><td><ul><li>A file with the j attribute has all of its data written to the <a href="/facts/Ext3/VSEhX1WQ">ext3</a> journal before being written to the file itself, if the filesystem is mounted with the "data=ordered" or "data=writeback" options.</li><li>When the filesystem is mounted with the "data=journal" option all file data is already <a href="/facts/Journaling_file_system/UCAaSBrD">journaled</a>, so this attribute has no effect.</li></ul></td></tr><tr><th>Secure deletion</th><td>s</td><td>+s to set-s to clear<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a><a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a></td><td><ul><li>When a file with the s attribute set is deleted, <a href="/facts/Data_remanence/xW7XvQsn">its blocks are zeroed</a> and written back to the disk.</li></ul></td></tr><tr><th>Synchronous updates</th><td>S</td><td>+S to set-S to clear</td><td><ul><li>When a file with the S attribute set is modified, the changes are written synchronously on the disk; this is equivalent to the 'sync' mount option applied to a subset of the files.</li><li>This is equivalent to the sync <a href="/facts/Mount_(Unix)/VlDPf1Hm">mount option</a>, applied to a subset of the files.</li></ul></td></tr><tr><th>Top of directory hierarchy</th><td>T</td><td>+T to set-T to clear</td><td><ul><li>A directory with the T attribute will be deemed to be the top of directory hierarchies for the purposes of the <a href="/facts/Orlov_block_allocator/z8fY3kkc">Orlov block allocator</a>.</li><li>This is a hint to the block allocator used by <a href="/facts/Ext3/VSEhX1WQ">ext3</a> and <a href="/facts/Ext4/zFbQRpsh">ext4</a> that the subdirectories under this directory are not related, and thus should be spread apart for allocation purposes.</li><li>For example: it is a very good idea to set the T attribute on the /home directory, so that /home/john and /home/mary are placed into separate block groups.</li><li>For directories where this attribute is not set, the Orlov block allocator will try to group subdirectories closer together where possible.</li></ul></td></tr><tr><th>No tail-merging</th><td>t</td><td>+t to set-t to clear</td><td><ul><li>For those filesystems that support <a href="/facts/Block_suballocation/t2l4N01d">tail-merging</a>, a file with the t attribute will not have a partial block fragment at the end of the file merged with other files.</li><li>This is necessary for applications such as <a href="/facts/LILO_(boot_loader)/CSlDBvwD">LILO</a>, which reads the filesystem directly and doesn't understand tail-merged files.</li></ul></td></tr><tr><th>Undeletable</th><td>u</td><td>+u to set-u to clear<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a></td><td><ul><li>When a file with the u attribute set is deleted, its contents are saved.</li><li>This allows the user to ask for its <a href="/facts/Undeletion/RJHzHYdn">undeletion</a>.</li></ul></td></tr><tr><th>Compression raw access</th><td>X</td><td><i>(unavailable)</i></td><td><ul><li>The X attribute is used by the experimental compression patches to indicate that a raw contents of a compressed file can be accessed directly.</li></ul></td></tr><tr><th>Compressed dirty file</th><td>Z</td><td><i>(unavailable)</i></td><td><ul><li>The Z attribute is used by the experimental compression patches to indicate a compressed file is "dirty".</li></ul></td></tr><tr><th>Version / generation number</th><td>-v</td><td>-v <i>version</i></td><td><ul><li>File's version/generation number.</li></ul></td></tr></tbody></table> <h4>Notes</h4> <h2 id="in-bsd-like-systems-chflags">In BSD-like systems (chflags)</h2> <h3>File system support</h3> <p>The chflags command is not specific to particular file systems. <a href="/facts/Unix_File_System/wDMLrTPe">UFS</a> on BSD systems, and <a href="/facts/APFS/y16sIvSM">APFS</a>, <a href="/facts/HFS%2B/sWk14kM5">HFS+</a>, <a href="/facts/Server_Message_Block/pWM35pl8">SMB</a>, <a href="/facts/Apple_Filing_Protocol/LVdUujjq">AFP</a>, and <a href="/facts/File_Allocation_Table/uFvpmWxa">FAT</a> on macOS support at least some flags. </p> <h3>chflags description</h3> <p>The form of the chflags command is: </p> chflags [-R [-H | -L | -P]] flags file ... <ul><li>-H If the -R option is specified, symbolic links on the command line are followed. (Symbolic links encountered in the tree traversal are not followed.)</li> <li>-L If the -R option is specified, all symbolic links are followed.</li> <li>-P If the -R option is specified, no symbolic links are followed. This is the default.</li> <li>-R Change the file flags for the file hierarchies rooted in the files instead of just the files themselves.</li></ul> <h3>Displaying</h3> <p>BSD-like systems, in general, have no default user-level command specifically meant to display the flags of a file. The <a href="/facts/Ls/5GsH3v2a">ls command</a> will do with either the -lo, or the -lO, depending on the system, flags passed. </p> <h3>Attributes</h3> <p>All traditional attributes can be set or cleared by the super-user; some can also be set or cleared by the owner of the file. Some attributes include: </p> File attributes<table><tbody><tr><th>Attribute</th><th>ls flag</th><th>chflags flag</th><th>Owner-settable</th><th>OS support</th><th>Semantics and rationale</th></tr><tr><th>Archived</th><td>arch</td><td>arch, archived</td><td>No</td><td>All</td><td>File is archived</td></tr><tr><th>Opaque</th><td>opaque</td><td>opaque</td><td>Yes</td><td>All</td><td>Directory is opaque when viewed through a union mount</td></tr><tr><th>No dump</th><td>nodump</td><td>nodump</td><td>Yes</td><td>All</td><td>File cannot be dumped</td></tr><tr><th>System append-only</th><td>sappnd</td><td>sappnd, sappend</td><td>No</td><td>All</td><td>Existing data in the file can't be overwritten and the file cannot be truncated</td></tr><tr><th>User append-only</th><td>uappnd</td><td>uappnd, uappend</td><td>Yes</td><td>All</td><td>Existing data in the file can't be overwritten and the file cannot be truncated</td></tr><tr><th>System immutable</th><td>schg</td><td>schg, schange, simmutable</td><td>No</td><td>All</td><td>File cannot be changed, renamed, moved, or removed</td></tr><tr><th>User immutable</th><td>uchg</td><td>uchg, uchange, uimmutable</td><td>Yes</td><td>All</td><td>File cannot be changed, renamed, moved, or removed</td></tr><tr><th>System no-unlink</th><td>sunlnk</td><td>sunlnk, sunlink</td><td>No</td><td>FreeBSD, DragonFly BSD, macOS</td><td>File cannot be removed, renamed or mounted on; on macOS this flag needs to be set or cleared from <a href="/facts/Single_user_mode/GFYQSDke">single user mode</a></td></tr><tr><th>User no-unlink</th><td>uunlnk</td><td>uunlnk, uunlink</td><td>Yes</td><td>FreeBSD, DragonFly BSD</td><td>File cannot be removed, renamed or mounted on</td></tr><tr><th>Hidden</th><td>hidden</td><td>hidden</td><td>Yes</td><td>macOS</td><td>File is hidden by default in the GUI (but not in ls)</td></tr><tr><th>Hidden</th><td>hidden</td><td>hidden, uhidden</td><td>Yes</td><td>FreeBSD</td><td>File might be hidden by default in some GUI desktops (but not in ls)</td></tr><tr><th>Tracked</th><td>tracked</td><td>tracked</td><td>Yes</td><td>macOS</td><td>File modifications and deletions are tracked</td></tr><tr><th>Restricted</th><td>restricted</td><td>restricted</td><td>No</td><td>macOS</td><td>File is protected by <a href="/facts/System_Integrity_Protection/hpVHcqRh">System Integrity Protection</a>; accompanied by the <a href="/facts/Extended_file_attributes/1wmerAyK">extended attribute</a> com.apple.rootless; flag needs to be set or cleared from Recovery Mode</td></tr><tr><th>Compressed</th><td>compressed</td><td></td><td>No</td><td>macOS</td><td>File is <a href="/facts/HFS_Plus/sWk14kM5">HFS</a>-compressed (read-only flag); not available on <a href="/facts/APFS/y16sIvSM">APFS</a>-formatted volumes</td></tr><tr><th>Data Vault</th><td></td><td></td><td>No</td><td>macOS</td><td>Hidden privacy flag since <a href="/facts/MacOS_Mojave/QCehr08a">macOS Mojave</a> set by the core system to prohibit any access without special entitlements</td></tr><tr><th>Offline</th><td>offline</td><td>offline, uoffline</td><td>Yes</td><td>FreeBSD</td><td>File is offline</td></tr><tr><th>Snapshot</th><td>snapshot</td><td></td><td>No</td><td>FreeBSD, NetBSD</td><td>File is a snapshot file (read-only flag)</td></tr><tr><th>Sparse</th><td>sparse</td><td>sparse, usparse</td><td>Yes</td><td>FreeBSD</td><td>Writes of all zeroes may be written as "holes"</td></tr><tr><th>Must be archived</th><td>uarch</td><td>uarch, uarchive</td><td>Yes</td><td>FreeBSD</td><td>File must be archived</td></tr></tbody></table> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/ATTRIB/t81evL39">ATTRIB</a> – analogous command in MS-DOS, OS/2 and Microsoft Windows</li> <li><a href="/facts/Chown/JPm7Xv6u">chown</a> – change file/directory ownership in a Unix system</li> <li><a href="/facts/Chmod/aGRdWvvk">chmod</a> – change file access control attributes in a Unix system</li> <li><a href="/facts/Cacls/6x6KPPum">cacls</a> – change file access control lists in Microsoft Windows NT</li></ul> <h2 id="notes">Notes</h2> <ul><li><a href="https://linux.die.net/man/1/chattr">chattr(1)</a> – <a href="/facts/Linux/9FvCKSTq">Linux</a> User Commands <a href="/facts/Man_page/S2yYjy0J">Manual</a></li> <li><a href="https://linux.die.net/man/1/lsattr">lsattr(1)</a> – <a href="/facts/Linux/9FvCKSTq">Linux</a> User Commands <a href="/facts/Man_page/S2yYjy0J">Manual</a></li> <li><a href="https://man.openbsd.org/chflags.1">chflags(1)</a> – <a href="/facts/OpenBSD/xmPS9tek">OpenBSD</a> General Commands <a href="/facts/Man_page/S2yYjy0J">Manual</a></li> <li><a href="https://www.freebsd.org/cgi/man.cgi?query=chflags&sektion=1">chflags(1)</a> – <a href="/facts/FreeBSD/RKsFTm7F">FreeBSD</a> General Commands <a href="/facts/Man_page/S2yYjy0J">Manual</a></li> <li><a href="https://man.netbsd.org/chflags.1">chflags(1)</a> – <a href="/facts/NetBSD/PTm5HWls">NetBSD</a> General Commands <a href="/facts/Man_page/S2yYjy0J">Manual</a></li> <li><a href="https://keith.github.io/xcode-man-pages/chflags.1.html">chflags(1)</a> – <a href="/facts/Darwin_(operating_system)/DogI3ptd">Darwin</a> and <a href="/facts/MacOS/Y93vVpTm">macOS</a> General Commands <a href="/facts/Man_page/S2yYjy0J">Manual</a> (outdated; see <a href="https://www.unix.com/man-page/osx/1/chflags/">newer version</a>)</li> <li><a href="https://github.com/apple/darwin-xnu/blob/master/bsd/sys/stat.h#L466-L519">stat.h</a> (flags section in the BSD system source code of the macOS <a href="/facts/XNU/dUCpExf0">XNU</a> kernel)</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>chmod(1) – illumos and OpenSolaris User Commands Reference Manual from latest Sun based OpenSolaris <a href="http://schillix.org/opensolarisman/man1/chmod.1.html" target="_blank">http://schillix.org/opensolarisman/man1/chmod.1.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>ls(1) – illumos and OpenSolaris User Commands Reference Manual from latest Sun based OpenSolaris <a href="http://schillix.org/opensolarisman/man1/ls.1.html" target="_blank">http://schillix.org/opensolarisman/man1/ls.1.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>chflags(1) – OpenBSD General Commands Manual <a href="https://man.openbsd.org/chflags.1" target="_blank">https://man.openbsd.org/chflags.1</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear these attributes. <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>These attributes are not honored by the ext2 and ext3 filesystems as implemented in the current mainline Linux kernels. <a href="/wiki/Ext2" target="_blank">/wiki/Ext2</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>These attributes only make sense for Copy-on-Write file-systems such as btrfs. <a href="/wiki/Btrfs" target="_blank">/wiki/Btrfs</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear these attributes. <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Only the superuser or a process possessing the CAP_SYS_RESOURCE capability can set or clear this attribute. <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>These attributes are not honored by the ext2 and ext3 filesystems as implemented in the current mainline Linux kernels. <a href="/wiki/Ext2" target="_blank">/wiki/Ext2</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>This attribute is not honored by the ext4 filesystem as implemented in the current mainline Linux kernels as reported in Bug #17872. <a href="/wiki/Ext4" target="_blank">/wiki/Ext4</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>These attributes are not honored by the ext2 and ext3 filesystems as implemented in the current mainline Linux kernels. <a href="/wiki/Ext2" target="_blank">/wiki/Ext2</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> </ol>