Linux "chattr" Command Line Options and Examples
change file attributes on a Linux file system
chattr changes the file attributes on a Linux file system. The format of a symbolic mode is +-=[aAcCdDeijPsStTu]. The operator '+' causes the selected attributes to be added to the existing attributes of the files; '-' causes them to be removed; and '=' causes them to be the only attributes that the files have.
chattr [ -RVf ] [ -v version ] [ -p project ] [ mode ] files...
Command Line Options:
Recursively change attributes of directories and their contents.
chattr -R ...
Be verbose with chattr's output and print the program version.
chattr -V ...
Suppress most error messages.
chattr -f ...
Set the file's version/generation number.
chattr -v ...
Set the file's project number.ATTRIBUTESA file with the 'a' attribute set can only be open in append mode for writing. Only the superuser or a process possessing theCAP_LINUX_IMMUTABLE capability can set or clear this attribute.When a file with the 'A' attribute set is accessed, its atime record is not modified. This avoids a certain amount of disk I/O forlaptop systems.A file with the 'c' attribute set is automatically compressed on the disk by the kernel. A read from this file returns uncompresseddata. A write to this file compresses data before storing them on the disk. Note: please make sure to read the bugs and limitationssection at the end of this document.A file with the 'C' attribute set will not be subject to copy-on-write updates. This flag is only supported on file systems whichperform copy-on-write. (Note: For btrfs, the 'C' flag should be set on new or empty files. If it is set on a file which already hasdata blocks, it is undefined when the blocks assigned to the file will be fully stable. If the 'C' flag is set on a directory, itwill have no effect on the directory, but new files created in that directory will have the No_COW attribute set.)A file with the 'd' attribute set is not candidate for backup when the dump(8) program is run.When a directory with the 'D' attribute set is modified, the changes are written synchronously on the disk; this is equivalent to the'dirsync' mount option applied to a subset of the files.The 'e' attribute indicates that the file is using extents for mapping the blocks on disk. It may not be removed using chattr(1).The 'E' attribute is used by the experimental encryption patches to indicate that the file has been encrypted. It may not be set orreset using chattr(1), although it can be displayed by lsattr(1).A file with the 'i' attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file, most of thefile's metadata can not be modified, and no data can be written to the file. Only the superuser or a process possessing theCAP_LINUX_IMMUTABLE capability can set or clear this attribute.The 'I' attribute is used by the htree code to indicate that a directory is being indexed using hashed trees. It may not be set orreset using chattr(1), although it can be displayed by lsattr(1).A file with the 'j' attribute has all of its data written to the ext3 or ext4 journal before being written to the file itself, if thefile system is mounted with the "data=ordered" or "data=writeback" options and the file system has a journal. When the filesystem ismounted with the "data=journal" option all file data is already journalled and this attribute has no effect. Only the superuser or aprocess possessing the CAP_SYS_RESOURCE capability can set or clear this attribute.A file with the 'N' attribute set indicates that the file has data stored inline, within the inode itself. It may not be set or resetusing chattr(1), although it can be displayed by lsattr(1).A directory with the 'P' attribute set will enforce a hierarchical structure for project id's. This means that files and directorycreated in the directory will inherit the project id of the directory, rename operations are constrained so when a file or directoryis moved into another directory, that the project id's much match. In addition, a hard link to file can only be created when theproject id for the file and the destination directory match.When a file with the 's' attribute set is deleted, its blocks are zeroed and written back to the disk. Note: please make sure toread the bugs and limitations section at the end of this document.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.A file with the 't' attribute will not have a partial block fragment at the end of the file merged with other files (for thosefilesystems which support tail-merging). This is necessary for applications such as LILO which read the filesystem directly, andwhich don't understand tail-merged files. Note: As of this writing, the ext2 or ext3 filesystems do not (yet, except in very experi‐mental patches) support tail-merging.A directory with the 'T' attribute will be deemed to be the top of directory hierarchies for the purposes of the Orlov block alloca‐tor. This is a hint to the block allocator used by ext3 and ext4 that the subdirectories under this directory are not related, andthus should be spread apart for allocation purposes. For example it is a very good idea to set the 'T' attribute on the /homedirectory, so that /home/john and /home/mary are placed into separate block groups. For directories where this attribute is not set,the Orlov block allocator will try to group subdirectories closer together where possible.When a file with the 'u' attribute set is deleted, its contents are saved. This allows the user to ask for its undeletion. Note:please make sure to read the bugs and limitations section at the end of this document.AUTHORchattr was written by Remy Card <Remy.Card@linux.org>. It is currently being maintained by Theodore Ts'o <firstname.lastname@example.org>.BUGS AND LIMITATIONSThe 'c', 's', and 'u' attributes are not honored by the ext2, ext3, and ext4 filesystems as implemented in the current mainlineLinux kernels.The 'j' option is only useful for ext3 and ext4 file systems.The 'D' option is only useful on Linux kernel 2.5.19 and later.AVAILABILITYchattr is part of the e2fsprogs package and is available from http://e2fsprogs.sourceforge.net.
chattr -p ...