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20150420-2 选题
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Managing file & directory attributes in linux using chattr & lsattr command
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================================================================================
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There are certain control attributes that may be set on a file or directory in order to allow data to be appended, to prevent it from being changed or deleted, etc. For example, you can enable attributes on a critical system file or directory so that no users, including root, can delete or change it, disallow a backup utility such as the dump command to back up a specific file or directory, and so on. These attributes can only be set on files and directories located in an ext2, ext3, or an ext4 file system
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There are two commands **lsattr** and **chattr** that are used for attribute management. The following is the list of commonly used attributes
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注：表格代码
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<table width="482" cellspacing="0" cellpadding="4" style="height: 651px">
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<colgroup>
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<col width="112">
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<col width="514"> </colgroup>
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<tbody>
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<tr valign="top">
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<td width="112">
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<p align="justify" class="western"><b>Attributes</b></p>
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</td>
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<td width="514">
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<p align="justify" class="western"><b>Description</b></p>
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</td>
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</tr>
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<tr valign="top">
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<td width="112">
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<p align="justify" class="western">a (append)</p>
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</td>
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<td width="514">
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<p align="justify" class="western">Append operation is allowed on the file</p>
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</td>
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</tr>
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<tr valign="top">
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<td width="112">
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<p align="justify" class="western">A</p>
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</td>
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<td width="514">
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<p align="justify" class="western">This attribute will not allow to update access time of a file</p>
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</td>
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</tr>
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<tr valign="top">
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<td width="112">
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<p align="justify" class="western">c (compressed)</p>
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</td>
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<td width="514">
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<p align="justify" class="western">When this attribute is enable then file is compressed on the disk automatically</p>
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</td>
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</tr>
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<tr valign="top">
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<td width="112">
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<p align="justify" class="western">d (dump)</p>
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</td>
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<td width="514">
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<p align="justify" class="western">File cannot be backed up using the dump command.</p>
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</td>
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</tr>
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<tr valign="top">
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<td width="112">
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<p align="justify" class="western">D</p>
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</td>
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<td width="514">
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<p align="justify" class="western">When D attribute is set on directory then changes are stored synchronously on the disk</p>
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</td>
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</tr>
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<tr valign="top">
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<td width="112">
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<p align="justify" class="western">e (extent format)</p>
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</td>
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<td width="514">
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<p align="justify" class="western">It shows that the file is using extents for mapping the blocks on disk</p>
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</td>
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</tr>
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<tr valign="top">
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<td width="112">
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<p align="justify" class="western">i (immutable)</p>
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</td>
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<td width="514">
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<p align="justify" class="western">When this attribute is enable on file then we cannot be altered, renamed and delete file.</p>
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</td>
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</tr>
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<tr valign="top">
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<td width="112">
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<p align="justify" class="western">j (journaling)</p>
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</td>
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<td width="514">
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<p align="justify" class="western">When this attribute is set then file’s data is stored in journal first then written to file.</p>
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</td>
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</tr>
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<tr valign="top">
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<td width="112">
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<p align="justify" class="western">S (synchronous)</p>
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</td>
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<td width="514">
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<p align="justify" class="western">When this attribute is set , then changes or modifications are stored synchronously on the disk</p>
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</td>
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</tr>
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</tbody>
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</table>
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Different Options that can be used in chattr Command :
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- **-R** change attributes of directory and its sub-directories recursively
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- **-V** Verbose output of chattr command along with version.
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- **-f** Suppress most error messages.
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**Operators** that are used in chattr command to set and unset attributes
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- The ‘+’ sign is used to set attribute on the files and directories,
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- The ‘-‘ sign is used to remove or unset the attribute
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- The ‘=’ sign causes them to be the only attributes that the files have.
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Basic Syntax of **chattr** and **lsattr** command :
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# chattr <options> <attributes> <file or Directory >
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# lsattr <File or Directory>
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### Example:1 Make a file immutable using ‘i’ attribute ###
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[root@linuxtechi ~]# chattr +i dummy_data
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[root@linuxtechi ~]# lsattr dummy_data
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----i----------- dummy_data
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Now try to remove and edit the File
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[root@linuxtechi ~]# rm -f dummy_data
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rm: cannot remove ‘dummy_data’: Operation not permitted
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[root@linuxtechi ~]# echo "test" >> dummy_data
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-bash: dummy_data: Permission denied
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### Example:2 Remove the immutable attribute ###
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[root@linuxtechi ~]# chattr -i dummy_data
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[root@linuxtechi ~]# lsattr dummy_data
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---------------- dummy_data
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### Example:3 To allow only append operations on the file ###
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[root@linuxtechi ~]# chattr +a dummy_data
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[root@linuxtechi ~]# lsattr dummy_data
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-----a---------- dummy_data
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Now try to append the contents of fstab file in dummy_data file
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[root@linuxtechi ~]# cat /etc/fstab >> dummy_data
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[root@linuxtechi ~]#
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### Example :4 Secure Directory and its sub-directories using -R option and ‘+i’ attribute. ###
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Let’s create a directory sysadmin and its subdirectories
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[root@linuxtechi ~]# mkdir sysadmin
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[root@linuxtechi ~]# mkdir sysadmin/admim_{1,2,3,4,5}
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[root@linuxtechi ~]# ls -l sysadmin/
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total 0
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drwxr-xr-x. 2 root root 6 Apr 19 09:50 admim_1
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drwxr-xr-x. 2 root root 6 Apr 19 09:50 admim_2
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drwxr-xr-x. 2 root root 6 Apr 19 09:50 admim_3
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drwxr-xr-x. 2 root root 6 Apr 19 09:50 admim_4
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drwxr-xr-x. 2 root root 6 Apr 19 09:50 admim_5
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Set immutable attribute Recursively on the directory sysadmin
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[root@linuxtechi ~]# chattr -R +i sysadmin
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[root@linuxtechi ~]# lsattr -R sysadmin/
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----i----------- sysadmin/admim_1
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sysadmin/admim_1:
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----i----------- sysadmin/admim_2
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sysadmin/admim_2:
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----i----------- sysadmin/admim_3
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sysadmin/admim_3:
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----i----------- sysadmin/admim_4
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sysadmin/admim_4:
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----i----------- sysadmin/admim_5
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sysadmin/admim_5:
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[root@linuxtechi ~]#
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Now try to delete directories using rm command
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[root@linuxtechi ~]# rm -rf sysadmin
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rm: cannot remove ‘sysadmin/admim_1’: Permission denied
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rm: cannot remove ‘sysadmin/admim_2’: Permission denied
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rm: cannot remove ‘sysadmin/admim_3’: Permission denied
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rm: cannot remove ‘sysadmin/admim_4’: Permission denied
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rm: cannot remove ‘sysadmin/admim_5’: Permission denied
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[root@linuxtechi ~]#
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To unset the the attributes recursively use the below command
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[root@linuxtechi ~]# chattr -R -i sysadmin
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--------------------------------------------------------------------------------
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via: http://www.linuxtechi.com/file-directory-attributes-in-linux-using-chattr-lsattr-command/
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作者：[Pradeep Kumar][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[a]:http://www.linuxtechi.com/author/pradeep/
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