EXTATTRCTL(8) System Manager's Manual EXTATTRCTL(8)
NAME
extattrctlmanage UFS1 extended attributes
SYNOPSIS
extattrctl
start path
extattrctl
stop path
extattrctl
initattr [-f] [-p path] attrsize attrfile
extattrctl
showattr attrfile
extattrctl
enable path attrnamespace attrname attrfile
extattrctl
disable path attrnamespace attrname
DESCRIPTION
The extattrctl utility is the management utility for extended attributes over the UFS1 file system. It allows the starting and stopping of extended attributes on a file system, as well as initialization of attribute backing files, and enabling and disabling of specific extended attributes on a file system.
 
The first argument on the command line indicates the operation to be performed. Operation must be one of the following:
start path
Start extended attribute support on the file system named using path. The file system must be a UFS1 file system, and the UFS_EXTATTR kernel option must have been enabled.
stop path
Stop extended attribute support on the file system named using path. Extended attribute support must previously have been started.
initattr [-f] [-p path] attrsize attrfile
Create and initialize a file to use as an attribute backing file. You must specify a maximum per-inode size for the attribute in bytes in attrsize, as well as the file where the attribute will be stored, using attrfile.
 
The -f argument may be used to indicate that it is alright to overwrite an existing attribute backing file; otherwise, if the target file exists, an error will be returned.
 
The -p path argument may be used to preallocate space for all attributes rather than relying on sparse files to conserve space. This has the advantage of guaranteeing that space will be available for attributes when they are written, preventing low disk space conditions from denying attribute service.
 
This file should not exist before running initattr.
showattr attrfile
Show the attribute header values in the attribute file named by attrfile.
enable path attrnamespace attrname attrfile
Enable an attribute named attrname in the namespace attrnamespace on the file system identified using path, and backed by initialized attribute file attrfile. Available namespaces are “user” and “system”. The backing file must have been initialized using initattr before its first use. Attributes must have been started on the file system prior to the enabling of any attributes.
disable path attrnamespace attrname
Disable the attributed named attrname in namespace attrnamespace on the file system identified by path. Available namespaces are “user” and “system”. The file system must have attributes started on it, and the attribute most have been enabled using enable.
 
The kernel also includes support for automatic starting of extended attributes on a file system at mount time once configured with extattrctl. If the kernel is built with the UFS_EXTATTR_AUTOSTART option, UFS will search for a .attribute sub-directory of the file system root during the mount operation. If found, extended attribute support will be started for the file system. UFS will then search for system and user sub-directories of the .attribute directory for any potential backing files and enable an extended attribute for each valid backing file with the backing file name as the attribute name.
EXAMPLES
extattrctl start /
 
Start extended attributes on the root file system.
 
extattrctl initattr 17 /.attribute/system/md5
 
Create an attribute backing file in /.attribute/system/md5, and set the maximum size of each attribute to 17 bytes, with a sparse file used for storing the attributes.
 
extattrctl enable / system md5 /.attribute/system/md5
 
Enable an attribute named md5 on the root file system, backed from the file /.attribute/system/md5.
 
extattrctl disable / md5
 
Disable the attribute named md5 on the root file system.
 
extattrctl stop /
 
Stop extended attributes on the root file system.
SEE ALSO
HISTORY
Extended attribute support was developed as part of the TrustedBSD Project, and introduced in FreeBSD 5.0 and NetBSD 4.0. It was developed to support security extensions requiring additional labels to be associated with each file or directory.
AUTHORS
Robert N M Watson
BUGS
extattrctl works only on UFS1 file systems. The kernel support for extended attribute backing files and this control program should be generalized for any file system that lacks native extended attribute support.