Chattr

chattr is a Linux command that allows a user to set certain attributes on a file. Mostly chattr is used to make files "immutable" so that password files and certain system files cannot be erased during software upgrades.man|1|chflags|OpenBSD] It is analogous to the attrib command on DOS, OS/2 and Microsoft Windows operating systems, and "chflags" on modern BSD systems (including Mac OS X). Other Unix systems have no analogous commands; Solaris supports extended file attributes, but there are no user level commands for setting or changing them, and the chatr command in HP-UX, and chattr in AIX have unrelated functions.

yntax

The form of the chattr command is:

chattr [-RV] [-+=AacDdijsSu] [-v version] files

where

* -R is to recurse all subdirectories
* +i is to set the immutable bit to prevent even root from erasing or changing the contents a file.

Note: The superuser can't erase or write on the file, but he or she can set or unset the i attribute.

Attributes

Some attributes include:

* don't update atime (A)
* synchronous updates (S)
* synchronous directory updates (D)
* append only (a)
* compressed (c)
* no dump (d)
* immutable (i)
* data journalling (j)
* secure deletion (s)
* top of directory hierarchy (T)
* no tail-merging (t)
* undeletable (u)

See also

* lsattr – view file attributes
* chown – change file/directory ownership
* chmod – change file access control attributes
* cacls – Microsoft Windows NT file system ACL control utility

Notes

References

*man|1|chflags|OpenBSD
*man|1|chflags|FreeBSD