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mLine 1:
Line 1: − + − At first let's dump/restore a trivial process without external dependences.+ − * For that we can create a shell script, which will report date and time every second. For removing dependences on a current terminal it will be executed in a new session and output will be redirected in a file.+ + + + + + Line 9:
Line 14: − + + + + + + + − * Get pid of the test process:+ + + + − * Dump the test process. + − $ ~/crtools/crtools dump -t 2221 -vvv -o dump.log && echo OK + + + − * The state of the processes are saved in a few files:+ + + + + + + Line 31:
Line 53: − * Restore the test process.+ − $ ~/crtools/crtools restore -d -t 2221 -vvv -o restore.log && echo OK + + + + + − + − + + + + + + + + Line 42:
Line 75: − + − $ ~/crtools/crtools dump -t 2621 + + + + − crtools asks to set the option --shell-job, because we try to dump only a part of session and a slave point of a tty pair. It's a common rule to ask a user, if only a part of something is dumped.+ − $ ~/crtools/crtools dump -vvvv -o dump.log -t 2621 --shell-job && echo Ok + − Ok + − $ ~/crtools/crtools restore -vvvv -o restore.log -t 2621 --shell-job + + + + + + + +
→Dump: Add a single line tip
= Dumping a simplest process in a new session without controll terminal =
This HOWTO describes how to dump a trivial program.
== Simplest case ==
=== Prepare ===
Let's create a shell script which loops and reports time every second:
$ cat > test.sh <<-EOF
$ cat > test.sh <<-EOF
#!/bin/sh
#!/bin/sh
done
done
EOF
EOF
$ chmod +x test.sh
$ chmod +x test.sh
=== Run (isolated) ===
Now, if you try to simply run and try to dump such a program, criu will fail. The reason is a program you launch from the shell shares some common resources with the shell, notably its session and terminal. Criu has a built-in check that makes sure there are no such resources.
To remove the dependency on a current terminal, let's executed our script in a new session and redirect its output to a file:
$ setsid ./test.sh < /dev/null &> test.log &
$ setsid ./test.sh < /dev/null &> test.log &
[2] 2220
[2] 2220
[2]+ Done setsid ./test.sh < /dev/null &>test.log
[2]+ Done setsid ./test.sh < /dev/null &>test.log
=== Dump ===
Get the PID of the test process:
$ ps -C test.sh
$ ps -C test.sh
PID TTY TIME CMD
PID TTY TIME CMD
2221 ? 00:00:00 test.sh
2221 ? 00:00:00 test.sh
Dump it:
# criu dump -t 2221 -vvv -o dump.log && echo OK
OK
OK
'''Tip:''' Alternatively, you can combine both steps into a single command: <code># criu dump -t $(pgrep test.sh) -v4 -o dump.log</code>
=== Check dump files ===
The state of the process(es) is saved to a few files:
$ ls
$ ls
core-2221.img eventpoll-tfd.img filelocks-2221.img inotify.img netlinksk.img pipes.img sigacts-2424.img test.log
core-2221.img eventpoll-tfd.img filelocks-2221.img inotify.img netlinksk.img pipes.img sigacts-2424.img test.log
eventfd.img fifo-data.img ids-2424.img mm-2221.img pages-2.img rlimit-2424.img signal-s-2424.img vmas-2221.img
eventfd.img fifo-data.img ids-2424.img mm-2221.img pages-2.img rlimit-2424.img signal-s-2424.img vmas-2221.img
eventpoll.img fifo.img inetsk.img mm-2424.img pipes-data.img sigacts-2221.img sk-queues.img vmas-2424.img
eventpoll.img fifo.img inetsk.img mm-2424.img pipes-data.img sigacts-2221.img sk-queues.img vmas-2424.img
=== Restore ===
Restore the test process:
# criu restore -d -vvv -o restore.log && echo OK
OK
OK
= Dumping one shell job =
== A shell job ==
Now let's try to dump a program, which is using a terminal. For that we need to execute our test script or another program (e.g. "top") from a terminal without redirections. It will report date and time every second. crtools supports only [http://en.wikipedia.org/wiki/Pseudo_terminal Unix98 PTYs].
Now let's see how to dump the same program when it is just started from the shell without any additional setsid and stdio redirection.
For that we need to execute our test script or another program (e.g. "top") from a terminal without any redirection.
Note criu only supports [http://en.wikipedia.org/wiki/Pseudo_terminal Unix98 PTYs].
=== Run ===
$ ./test.sh
$ ./test.sh
$ ps -C test.sh
$ ps -C test.sh
2621 pts/1 00:00:00 test.sh
2621 pts/1 00:00:00 test.sh
Currently crtools doesn't support a stopped task, so "crtools dump" must be executed from another terminal.
=== Dump ===
Currently criu doesn't support a stopped task, so "criu dump" must be executed from another terminal.
# criu dump -t 2621
(00.012929) Error (tty.c:1022): tty: Found dangling tty with sid 940 pgid 2621 (pts) on peer fd 0. Consider using --shell-job option.
(00.012929) Error (tty.c:1022): tty: Found dangling tty with sid 940 pgid 2621 (pts) on peer fd 0. Consider using --shell-job option.
(00.013111) Error (cr-dump.c:1636): Dumping FAILED.
(00.013111) Error (cr-dump.c:1636): Dumping FAILED.
See, criu asks to set the <code>--shell-job</code>, because we try to dump only a part of a session and a slave end of a tty pair. It is a common rule to ask a user, if only a part of something is dumped.
# criu dump -vvvv -o dump.log -t 2621 --shell-job && echo OK
OK
=== Restore ===
# criu restore -vvvv -o restore.log --shell-job
Fri Apr 12 12:41:09 MSK 2013
Fri Apr 12 12:41:09 MSK 2013
Fri Apr 12 12:41:10 MSK 2013
Fri Apr 12 12:41:10 MSK 2013
[[Category:HOWTO]]