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−First of all, if you try to simply launch such program and dump it crtools will fail. This is because the program you launch from shell shared session and terminal with the shell itself, but crtools should make sure, that no resources are used by external processes. So this simple test would be a little bit trickier, that just it.+
+
+== Dumping a simplest process in a new session without control terminal ==
−* For that we can create a shell script, which will report date and time every second. For removing dependencies on a current terminal it will be executed in a new session and output will be redirected in a file.
* 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:+
+
+
* Restore the test process.+
− $ ~/crtools/crtools restore -d -t 2221 -vvv -o restore.log && echo OK+
+
+
+
+
+For that we need to execute our test script or another program (e.g. "top") from a terminal without redirections. crtools supports only [http://en.wikipedia.org/wiki/Pseudo_terminal Unix98 PTYs].
$ ~/crtools/crtools dump -t 2621+
+
− $ ~/crtools/crtools dump -vvvv -o dump.log -t 2621 --shell-job && echo Ok+ Ok+
+
+
This HOWTO describes how to dump a very simple shell scripts that just loops and shows that it's alive.
+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
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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, crtools will fail. The reason is a program you launch from the shell shares some common resources with the shell, notably its session and terminal. Crtools 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:
+ # crtools dump -t 2221 -vvv -o dump.log && echo OK
OK
OK
−=== 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
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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:
+ # crtools restore -d -t 2221 -vvv -o restore.log && echo OK
OK
OK
−== Dumping one shell job ==
+== A shell job ==
−Now let's see how to dump the same program when it is just launched from shell without additional setsid-s and stdio-s redirection.
+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 crtools only supports [http://en.wikipedia.org/wiki/Pseudo_terminal Unix98 PTYs].
+=== Run ===
− $ ./test.sh
$ ./test.sh
$ ps -C test.sh
$ ps -C test.sh
PID TTY TIME CMD
PID TTY TIME CMD
2621 pts/1 00:00:00 test.sh
2621 pts/1 00:00:00 test.sh
+
+=== Dump ===
Currently crtools doesn't support a stopped task, so "crtools dump" must be executed from another terminal.
Currently crtools doesn't support a stopped task, so "crtools dump" must be executed from another terminal.
− # crtools 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.
−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.
+See, crtools 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.
− # crtools dump -vvvv -o dump.log -t 2621 --shell-job && echo OK
+ OK
+=== Restore ===
+ $ ~/crtools/crtools restore -vvvv -o restore.log -t 2621 --shell-job
$ ~/crtools/crtools restore -vvvv -o restore.log -t 2621 --shell-job
Fri Apr 12 12:41:09 MSK 2013
Fri Apr 12 12:41:09 MSK 2013