diff options
Diffstat (limited to 'misc/chattr.1.in')
| -rw-r--r-- | misc/chattr.1.in | 59 |
1 files changed, 34 insertions, 25 deletions
diff --git a/misc/chattr.1.in b/misc/chattr.1.in index 92f6d703..2a3640c6 100644 --- a/misc/chattr.1.in +++ b/misc/chattr.1.in @@ -19,17 +19,18 @@ chattr \- change file attributes on a Linux file system .B chattr changes the file attributes on a Linux file system. .PP -The format of a symbolic mode is +-=[acdeijstuADST]. +The format of a symbolic mode is +-=[acdeijstuACDST]. .PP 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. .PP -The letters `acdeijstuADST' select the new attributes for the files: +The letters `acdeijstuACDST' select the new attributes for the files: append only (a), compressed (c), no dump (d), extent format (e), immutable (i), -data journalling (j), secure deletion (s), no tail-merging (t), -undeletable (u), no atime updates (A), synchronous directory updates (D), -synchronous updates (S), and top of directory hierarchy (T). +data journalling (j), secure deletion (s), no tail-merging (t), +undeletable (u), no atime updates (A), no copy on write (C), +synchronous directory updates (D), synchronous updates (S), +and top of directory hierarchy (T). .PP The following attributes are read-only, and may be listed by .BR lsattr (1) @@ -55,15 +56,24 @@ not modified. This avoids a certain amount of disk I/O for laptop systems. .PP A file with the `a' attribute set can only be open in append mode for writing. -Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE +Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute. .PP A file with the `c' attribute set is automatically compressed on the disk by the kernel. A read from this file returns uncompressed data. A write to -this file compresses data before storing them on the disk. Note: please +this file compresses data before storing them on the disk. Note: please make sure to read the bugs and limitations section at the end of this document. .PP +A file with the 'C' attribute set will not be subject to copy-on-write +updates. This flag is only supported on file systems which perform +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 has +data blocks, it is undefined when the blocks assigned to the file will +be fully stable. If the 'C' flag is set on a directory, it will have no +effect on the directory, but new files created in that directory will +the No_COW attribute.) +.PP 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. @@ -72,9 +82,9 @@ A file with the `d' attribute set is not candidate for backup when the .BR dump (8) program is run. .PP -The 'E' attribute is used by the experimental compression patches to +The 'E' attribute is used by the experimental compression patches to indicate that a compressed file has a compression error. It may not be -set or reset using +set or reset using .BR chattr (1), although it can be displayed by .BR lsattr (1). @@ -84,7 +94,7 @@ the blocks on disk. It may not be removed using .BR chattr (1). .PP 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 or reset using +is being indexed using hashed trees. It may not be set or reset using .BR chattr (1), although it can be displayed by .BR lsattr (1). @@ -102,11 +112,11 @@ to the file. Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute. .PP A file with the `j' attribute has all of its data written to the ext3 -journal before being written to the file itself, if the filesystem is -mounted with the "data=ordered" or "data=writeback" options. When the +or ext4 journal before being written to the file itself, if the filesystem +is mounted with the "data=ordered" or "data=writeback" options. When the filesystem is mounted with the "data=journal" option all file data -is already journalled and this attribute has no effect. -Only the superuser or a process possessing the CAP_SYS_RESOURCE +is already journalled and this attribute has no effect. Only +the superuser or a process possessing the CAP_SYS_RESOURCE capability can set or clear this attribute. .PP When a file with the `s' attribute set is deleted, its blocks are zeroed @@ -117,7 +127,7 @@ 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. .PP -A directory with the 'T' attribute will be deemed to be the top of +A directory with the 'T' attribute will be deemed to be the top of directory hierarchies for the purposes of the Orlov block allocator. This is a hint to the block allocator used by ext3 and ext4 that the subdirectories under this directory are not related, and thus should be @@ -129,7 +139,7 @@ group subdirectories closer together where possible. .PP A file with the 't' attribute will not have a partial block fragment at the end of the file merged with other files (for those filesystems which -support tail-merging). This is necessary for applications such as LILO +support tail-merging). This is necessary for applications such as LILO which read the filesystem directly, and which don't understand tail-merged files. Note: As of this writing, the ext2 or ext3 filesystems do not (yet, except in very experimental patches) support tail-merging. @@ -139,15 +149,15 @@ 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. .PP -The 'X' attribute is used by the experimental compression patches to +The 'X' attribute is used by the experimental compression patches to indicate that a raw contents of a compressed file can be accessed -directly. It currently may not be set or reset using +directly. It currently may not be set or reset using .BR chattr (1), although it can be displayed by .BR lsattr (1). .PP -The 'Z' attribute is used by the experimental compression patches to -indicate a compressed file is dirty. It may not be set or reset using +The 'Z' attribute is used by the experimental compression patches to +indicate a compressed file is dirty. It may not be set or reset using .BR chattr (1), although it can be displayed by .BR lsattr (1). @@ -157,12 +167,11 @@ although it can be displayed by was written by Remy Card <Remy.Card@linux.org>. It is currently being maintained by Theodore Ts'o <tytso@alum.mit.edu>. .SH BUGS AND LIMITATIONS -The `c', 's', and `u' attributes are not honored -by the ext2 and ext3 filesystems as implemented in the current mainline -Linux kernels. These attributes may be implemented -in future versions of the ext2 and ext3 filesystems. +The `c', 's', and `u' attributes are not honored +by the ext2, ext3, and ext4 filesystems as implemented in the current +mainline Linux kernels. .PP -The `j' option is only useful if the filesystem is mounted as ext3. +The `j' option is only useful if the filesystem is mounted as ext3 or ext4. .PP The `D' option is only useful on Linux kernel 2.5.19 and later. .SH AVAILABILITY |