CR in namespace - Revision history

Radostin: /* Limitations */ Shell jobs are supported by the 'criu-ns' script

2019-09-30T09:04:32Z

Limitations: Shell jobs are supported by the 'criu-ns' script

Xemul at 14:32, 17 September 2016

2016-09-17T14:32:14Z

Kir: moar

2016-09-08T23:21:29Z

moar

Kir: rewording

2016-09-08T22:38:06Z

rewording

Xemul at 18:02, 24 August 2016

2016-08-24T18:02:05Z

Xemul at 18:00, 24 August 2016

2016-08-24T18:00:45Z

Xemul: /* Known issues */

2016-08-24T18:00:28Z

Known issues

Xemul: Created page with "This page describes the criu-ns script that has appeared in criu-dev branch after 2.5 and is aimed at 2.6. == Problem == When restoring a process tree without namespaces (i...."

2016-08-24T17:58:37Z

Created page with "This page describes the criu-ns script that has appeared in criu-dev branch after 2.5 and is aimed at 2.6. == Problem == When restoring a process tree without namespaces (i...."

New page

This page describes the criu-ns script that has appeared in criu-dev branch after 2.5 and is aimed at 2.6.

== Problem ==

When restoring a process tree without namespaces (i.e. -- into the namespaces in which criu lives) one may frequently hit a "pid mismatch" problem. It is when a process we'd like to restore has a PID which is already owned by some other process living in this pid-namespace. There's no way one can restore a process tree in ''this'' namespace, so the only solution is to unshare the new pid namespace and restore the tree into it.

When doing so we have two problems

# In the new pid namespace someone has to become the "init" process
# In the new pid namespace we'd need to have new /proc mount which implies unsharing the mount namespace as well

And even if one solves the above problems, there will appear the third one -- when trying to dump the restore process tree ''again'' criu will likely refuse to dump the mount namespace, as it will be a complete clone of the original one and thus would likely contain many many unsupported mounts such as real devices, securityfs, trace/debug-fs etc. The latter can still be solved by nsenter-ing the process' pid and mount namespaces and doing the dump.

== Solution ==

All of the above -- the need to unshare stuff, getting pseudo-init, re-mounting /proc on dump and setns-ing on restore -- is solved by the scripts/criu-ns script. Just replace running one instead of regular criu run would do all of this, there's no need in doing anything with the CLI options, the API is fully compatible.

== Known issues ==

# The [[shell jobs]] are not supported
# The [[swrk mode]] is not supported
# Only the dump and restore is supported, so no [[Incremental dumps]] possible yet

@@ Line 22: / Line 22: @@
 == Limitations ==
 # The [[RPC#Swrk mode|swrk mode]] is not supported
 # Only the dump and restore are supported ([[incremental dumps]] are not possible)

@@ Line 3: / Line 3: @@
 == Problem ==
-When restoring a process tree without namespaces (i.e. into namespaces in which criu lives) one may frequently hit a "pid mismatch" problem. It happens when a process CRIU tries to restore has a PID which is already owned by some other process living in this pid namespace. There's no way one can restore a process tree in ''this'' namespace, so the only solution is to unshare the new pid namespace and restore the tree into it.
+When restoring a process tree without [[namespaces]] (i.e. into namespaces in which criu lives) one may frequently hit a "pid mismatch" problem. It happens when a process CRIU tries to restore has a PID which is already owned by some other process living in this pid namespace. There's no way one can restore a process tree in ''this'' namespace, so the only solution is to unshare the new pid namespace and restore the tree into it.
 When doing so we have two problems:

@@ Line 14: / Line 14: @@
 == Solution ==
-All of the above -- the need to unshare stuff, getting pseudo-init, re-mounting /proc on dump and setns-ing on restore -- is solved by the <code>scripts/criu-ns</code> script. Use it the same way you use regular criu binary, all command line options are the same.
+All of the above -- the need to unshare stuff, getting pseudo-init, re-mounting /proc on dump and setns-ing on restore -- is solved by the <code>scripts/criu-ns</code> script. It's a wrapper, use it the same way you use regular criu binary, all command line options are the same.
 == Limitations ==

@@ Line 3: / Line 3: @@
 == Problem ==
-When restoring a process tree without namespaces (i.e. -- into the namespaces in which criu lives) one may frequently hit a "pid mismatch" problem. It is when a process we'd like to restore has a PID which is already owned by some other process living in this pid-namespace. There's no way one can restore a process tree in ''this'' namespace, so the only solution is to unshare the new pid namespace and restore the tree into it.
+When restoring a process tree without namespaces (i.e. into namespaces in which criu lives) one may frequently hit a "pid mismatch" problem. It happens when a process CRIU tries to restore has a PID which is already owned by some other process living in this pid namespace. There's no way one can restore a process tree in ''this'' namespace, so the only solution is to unshare the new pid namespace and restore the tree into it.
-When doing so we have two problems
+When doing so we have two problems:
-# In the new pid namespace someone has to become the "init" process
+# In the new pid namespace, someone has to become the "init" process
-# In the new pid namespace we'd need to have new /proc mount which implies unsharing the mount namespace as well
+# In the new pid namespace, we'd need to have new /proc mount which implies unsharing the mount namespace as well
-And even if one solves the above problems, there will appear the third one -- when trying to dump the restore process tree ''again'' criu will likely refuse to dump the mount namespace, as it will be a complete clone of the original one and thus would likely contain many many unsupported mounts such as real devices, securityfs, trace/debug-fs etc. The latter can still be solved by nsenter-ing the process' pid and mount namespaces and doing the dump.
+Even if one solves the above problems, there will appear the third one -- when trying to dump the restore process tree ''again'' criu will likely refuse to dump the mount namespace, as it will be a complete clone of the original one and thus would likely contain many many unsupported mounts such as real devices, securityfs, trace/debug-fs etc. The latter can still be solved by nsenter-ing the process' pid and mount namespaces and doing the dump.
 == Solution ==
-All of the above -- the need to unshare stuff, getting pseudo-init, re-mounting /proc on dump and setns-ing on restore -- is solved by the scripts/criu-ns script. Just replace running one instead of regular criu run would do all of this, there's no need in doing anything with the CLI options, the API is fully compatible.
+All of the above -- the need to unshare stuff, getting pseudo-init, re-mounting /proc on dump and setns-ing on restore -- is solved by the <code>scripts/criu-ns</code> script. Use it the same way you use regular criu binary, all command line options are the same.
-== Known issues ==
+== Limitations ==
-# The [[Advanced usage#shell jobs C.2R|shell jobs]] are not supported
+# [[Advanced usage#shell jobs C.2R|Shell jobs]] are not supported
 # The [[RPC#Swrk mode|swrk mode]] is not supported
-# Only the dump and restore is supported, so no [[Incremental dumps]] possible yet
+# Only the dump and restore are supported ([[incremental dumps]] are not possible)
 [[Category:API]]
 [[Category:HOWTO]]

← Older revision		Revision as of 18:02, 24 August 2016
Line 21:		Line 21:
	# The [[RPC#Swrk mode\|swrk mode]] is not supported		# The [[RPC#Swrk mode\|swrk mode]] is not supported
	# Only the dump and restore is supported, so no [[Incremental dumps]] possible yet		# Only the dump and restore is supported, so no [[Incremental dumps]] possible yet
		+
		+	[[Category:API]]
		+	[[Category:HOWTO]]

← Older revision		Revision as of 18:00, 24 August 2016
Line 1:		Line 1:
−	This page describes the criu-ns script that has appeared in criu-dev branch after 2.5 and is aimed at 2.6.	+	This page describes the <code>criu-ns</code> script that has appeared in criu-dev branch after 2.5 and is aimed at 2.6.

	== Problem ==		== Problem ==