.\"
.\" Copyright (c) 2003 Matthew Dillon, All Rights Reserved.
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.\" $DragonFly: src/usr.bin/checkpt/checkpt.1,v 1.5 2007/06/30 19:20:48 swildner Exp $
.\"
.Dd October 19, 2003
.Dt CHECKPT 1
.Os
.Sh NAME
.Nm checkpt
.Nd resume checkpointed program
.Sh SYNOPSIS
.Nm
.Fl r Ar file.ckpt
.Sh DESCRIPTION
The
.Nm
utility will resume the checkpointed program from the specified checkpoint
file.
Programs can be checkpointed using ^E.
.Pp
By default, only members of the wheel group can checkpoint a program.
The group can be changed with the sysctl
.Va kern.ckptgroup .
The checkpoint file template can be changed with the sysctl
.Va kern.ckptfile .
.Pp
The checkpointing utility is fairly primitive.
Only programs operating on normal files can be properly restored.
Programs which operate on devices, sockets, or pipes (including piped
commands) cannot be completely.
File descriptors 0, 1, and 2, are not saved and the restored program will
inherit the descriptors from
.Nm .
.Pp
Programs can actively support checkpointing by catching the
.Dv SIGCKPT
signal, cleaning up, and manually calling the
.Fn sys_checkpoint
system call.
The program can then choose whether to continue running or exit.
The resumed program will get a (typically) positive return value from
.Fn sys_checkpoint
which it can use to determine whether it just made the system call or whether
it is being resumed from the system call.
The program can then reconstruct non-checkpointed elements and resume.
.Sh SEE ALSO
.Xr stty 1 ,
.Xr sys_checkpoint 2
.Sh HISTORY
The
.Nm
command first appeared in
.Dx 1.0 .