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Предыдущая версия справа и слева Предыдущая версия
Следующая версия 		Предыдущая версия
linux:selinux [2011/10/10 14:00]
linko22@gmail.com 		linux:selinux [2011/10/10 14:18] (текущий)
linko22@gmail.com [Re-Enabling SELinux]
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 ===== Overview ===== ===== Overview =====
  
-SELinux has two major components on your system. There's the kernel mechanism which is enforcing a bunch of access rules which apply to processes and files. And secondly, there's file labels : every file on your system has extra labels attached to it which tie-in with those access rules. Run ls -Z and you'll see what I mean.+SELinux has two major components on your system. There's the kernel mechanism which is enforcing a bunch of access rules which apply to processes and files. And secondly, there's file labels : **every** file on your system has extra labels attached to it which tie-in with those access rules. Run  
 +<code bash>ls -Z</code> 
 + and you'll see what I mean.
 ===== Should you really disable SELinux? ===== ===== Should you really disable SELinux? =====
  
 Be aware that by disabling SELinux you will be removing a security mechanism on your system. Think about this carefully, and if your system is on the Internet and accessed by the public, then think about it some more. Joshua Brindle (an SELinux developer) has comments on disabling SELinux here, which states clearly that applications should be fixed to work with SELinux, rather than disabling the OS security mechanism.  Be aware that by disabling SELinux you will be removing a security mechanism on your system. Think about this carefully, and if your system is on the Internet and accessed by the public, then think about it some more. Joshua Brindle (an SELinux developer) has comments on disabling SELinux here, which states clearly that applications should be fixed to work with SELinux, rather than disabling the OS security mechanism. 
 You need to decide if you want to disable SELinux temporarily to test the problem, or permanently switch it off. It may also be a better option to make changes to the policy to permit the operations that are being blocked - but this requires knowledge of writing policies and may be a steep learning curve for some people. For the operating system as a whole, there is two kinds of disabling: You need to decide if you want to disable SELinux temporarily to test the problem, or permanently switch it off. It may also be a better option to make changes to the policy to permit the operations that are being blocked - but this requires knowledge of writing policies and may be a steep learning curve for some people. For the operating system as a whole, there is two kinds of disabling:
-Permissive - switch the SELinux kernel into a mode where every operation is allowed. Operations that would be denied are allowed and a message is logged identifying that it would be denied. The mechanism that defines labels for files which are being created/changed is still active. +  * Permissive - switch the SELinux kernel into a mode where every operation is allowed. Operations that would be denied are allowed and a message is logged identifying that it would be denied. The mechanism that defines labels for files which are being created/changed is still active. 
-Disabled - SELinux is completely switched off in the kernel. This allows all operations to be permitted, and also disables the process which decides what to label files & processes with.+  *Disabled - SELinux is completely switched off in the kernel. This allows all operations to be permitted, and also disables the process which decides what to label files & processes with.
 Disabling SELinux could lead to problems if you want to re-enable it again later. When the system runs with file labelling disable it will create files with no label - which could cause problems if the system is booted into Enforcement mode. A full re-labelling of the file system will be necessary. Disabling SELinux could lead to problems if you want to re-enable it again later. When the system runs with file labelling disable it will create files with no label - which could cause problems if the system is booted into Enforcement mode. A full re-labelling of the file system will be necessary.
 ===== Temporarily switch off enforcement ===== ===== Temporarily switch off enforcement =====
  
 You can switch the system into permissive mode with the following command: You can switch the system into permissive mode with the following command:
-echo 0 >/selinux/enforce+ 
 +<code bash>echo 0 >/selinux/enforce</code> 
 You'll need to be logged in as root, and in the sysadm_r role: You'll need to be logged in as root, and in the sysadm_r role:
-newrole -r sysadm_r+ 
 +<code bash>newrole -r sysadm_r</code> 
 To switch back into enforcing mode: To switch back into enforcing mode:
-echo 1 >/selinux/enforce+ 
 +<code bash>echo 1 >/selinux/enforce</code>
 In Fedora Core and RedHat Enterprise Linux you can use the setenforce command with a 0 or 1 option to set permissive or enforcing mode, its just a slightly easier command than the above. In Fedora Core and RedHat Enterprise Linux you can use the setenforce command with a 0 or 1 option to set permissive or enforcing mode, its just a slightly easier command than the above.
 +
 To check what mode the system is in, To check what mode the system is in,
  
-cat /selinux/enforce+<code bash>cat /selinux/enforce</code> 
 which will print a "0" or "1" for permissive or enforcing - probably printed at the beginning of the line of the command prompt.  which will print a "0" or "1" for permissive or enforcing - probably printed at the beginning of the line of the command prompt. 
 ===== Permanently Permissive ===== ===== Permanently Permissive =====
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 In Fedora Core and RedHat Enterprise, edit /etc/selinux/config and you will see some lines like this: In Fedora Core and RedHat Enterprise, edit /etc/selinux/config and you will see some lines like this:
  
 +<code bash>
 # This file controls the state of SELinux on the system. # This file controls the state of SELinux on the system.
 # SELINUX= can take one of these three values: # SELINUX= can take one of these three values:
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 # strict - Full SELinux protection. # strict - Full SELinux protection.
 SELINUXTYPE=targeted SELINUXTYPE=targeted
-... just change SELINUX=enforcing to SELINUX=permissive, and you're done. Reboot if you want to prove it. +</code> 
-For the other Linuxes which don't have the /etc/selinux/config file, you just need to edit the kernel boot line, usually in /boot/grub/grub.conf if you're using the GRUB boot loader. On the kernel line, add enforcing=0 at the end. For example, +... just change **SELINUX=enforcing** to **SELINUX=permissive**, and you're done. Reboot if you want to prove it. 
 +For the other Linuxes which don't have the **/etc/selinux/config** file, you just need to edit the kernel boot line, usually in **/boot/grub/grub.conf** if you're using the GRUB boot loader. On the kernel line, add **enforcing=0** at the end. For example,
  
 +<code bash>
 title SE-Linux Test System title SE-Linux Test System
  root (hd0,0)  root (hd0,0)
  kernel /boot/vmlinuz-2.4.20-selinux-2003040709 ro root=/dev/hda1 nousb enforcing=0  kernel /boot/vmlinuz-2.4.20-selinux-2003040709 ro root=/dev/hda1 nousb enforcing=0
  #initrd /boot/initrd-2.4.20-selinux-2003040709.img  #initrd /boot/initrd-2.4.20-selinux-2003040709.img
 +</code>
 ===== Fully Disabling SELinux ===== ===== Fully Disabling SELinux =====
  
 Fully disabling SELinux goes one step further than just switching into permissive mode. Disabling will completely disable all SELinux functions including file and process labelling. Fully disabling SELinux goes one step further than just switching into permissive mode. Disabling will completely disable all SELinux functions including file and process labelling.
-In Fedora Core and RedHat Enterprise, edit /etc/selinux/config and change the SELINUX line to SELINUX=disabled: +In Fedora Core and RedHat Enterprise, edit **/etc/selinux/config** and change the SELINUX line to **SELINUX=disabled**:
  
 +<code bash>
 # This file controls the state of SELinux on the system. # This file controls the state of SELinux on the system.
 # SELINUX= can take one of these three values: # SELINUX= can take one of these three values:
Строка 67: Строка 78:
 # strict - Full SELinux protection. # strict - Full SELinux protection.
 SELINUXTYPE=targeted SELINUXTYPE=targeted
 +</code>
 ... and then reboot the system. ... and then reboot the system.
-For the other Linuxes which don't have the /etc/selinux/config file, you just need to edit the kernel boot line, usually in /boot/grub/grub.conf, if you're using the GRUB boot loader. On the kernel line, add selinux=0 at the end. For example, +For the other Linuxes which don't have the **/etc/selinux/config** file, you just need to edit the kernel boot line, usually in **/boot/grub/grub.conf**, if you're using the GRUB boot loader. On the kernel line, add **selinux=0** at the end. For example,
  
 +<code bash>
 title SE-Linux Test System title SE-Linux Test System
         root (hd0,0)         root (hd0,0)
         kernel /boot/vmlinuz-2.4.20-selinux-2003040709 ro root=/dev/hda1 nousb selinux=0         kernel /boot/vmlinuz-2.4.20-selinux-2003040709 ro root=/dev/hda1 nousb selinux=0
         #initrd /boot/initrd-2.4.20-selinux-2003040709.img         #initrd /boot/initrd-2.4.20-selinux-2003040709.img
 +</code>
 You will have to reboot to disable SELinux, you just can't do it while the system is running.  You will have to reboot to disable SELinux, you just can't do it while the system is running. 
 ===== Re-Enabling SELinux ===== ===== Re-Enabling SELinux =====
  
 If you've disabled SELinux as in the section above, and you want to enable it again then you've got a bit of work to do. The problem will be that files created or changed when SELinux was disabled won't have the correct file labels on them - if you just reboot in enforcing mode then a lot of stuff won't work properly. If you've disabled SELinux as in the section above, and you want to enable it again then you've got a bit of work to do. The problem will be that files created or changed when SELinux was disabled won't have the correct file labels on them - if you just reboot in enforcing mode then a lot of stuff won't work properly.
-What you need to do is to enable SELinux by editing /etc/selinux/config (for Fedora/RedHat) or by adding selinux=1 to the kernel boot line, then boot into permissive mode, then relabel everything, and then reboot into (or simply switch to) enforcing mode.+What you need to do is to enable SELinux by editing **/etc/selinux/config** (for Fedora/RedHat) or by adding **selinux=1** to the kernel boot line, then boot into **permissive** mode, then relabel everything, and then reboot into (or simply switch to) enforcing mode.
  
 After booting into permissive mode, run After booting into permissive mode, run
-fixfiles relabel+<code bash>fixfiles relabel</code>
 Alternatively, in Fedora and RedHat Enterprise Linux you can run Alternatively, in Fedora and RedHat Enterprise Linux you can run
-touch /.autorelabel+<code bash>touch /.autorelabel</code>
 and reboot or put and reboot or put
-autorelabel+<code bash>autorelabel</code>
 on the boot command line - in both cases the file system gets a full relabel early in the boot process. Note that this can take quite some time for systems with a large number of files. on the boot command line - in both cases the file system gets a full relabel early in the boot process. Note that this can take quite some time for systems with a large number of files.
  
 After relabelling the filesystem, you can switch to enforcing mode (see above) and your system should be fully enforcing again.  After relabelling the filesystem, you can switch to enforcing mode (see above) and your system should be fully enforcing again. 
linux/selinux.1318240838.txt.gz · Последнее изменение: 2011/10/10 14:00 — linko22@gmail.com

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