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.TH SNAP 4
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.SH NAME
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snap, snapfs \- create and mount process snapshots
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.SH SYNOPSIS
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.B snap
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[
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.B -o
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.I file
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]
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.I pid...
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.PP
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.B snapfs
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[
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.B -a
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]
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[
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.B -m
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.I mtpt
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]
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[
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.B -s
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.I service
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]
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.I file...
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.SH DESCRIPTION
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.I Snap
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and
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.I snapfs
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allow one to save and restore (static) process images,
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usually for debugging
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on a different machine or at a different time.
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.PP
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.I Snap
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writes a snapshot
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(see
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.IR snap (6))
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of the named processes to
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.I file
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(default standard output).
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If
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.I pid
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is a text string
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rather than a process id,
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.I snap
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will save all processes with
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that name that
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are owned by the current user.
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Both memory and text images are saved.
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.PP
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.I Snapfs
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is a file server that
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recreates the
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.B /proc
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directories for the processes in the snapshot.
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By default, it mounts the new directories
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into
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.B /proc
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before the current entries.
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The
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.B -m
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option can be used to specify
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an alternate mountpoint,
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while
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.B -a
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will cause it to mount the new directories
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after the current entries.
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The
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.B -s
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option causes it to serve requests via
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.BI /srv/ service.
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.SH EXAMPLE
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Suppose
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.I page
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has hung viewing Postscript on your terminal, but the author is gone for the rest of
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the month and you want to make sure the process
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is still around for debugging on his return.
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You can save the errant processes with
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.IP
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.EX
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snap -o page.snap `{psu | awk '$NF ~ /page|gs/ {print $2}'}
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.EE
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.PP
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When the author returns, he can add the process images to his name space
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by running
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.IP
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.EX
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snapfs page.snap
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.EE
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.PP
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and then use a conventional
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debugger to debug them.
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.SH SOURCE
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.B /sys/src/cmd/snap
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.SH SEE ALSO
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.IR acid (1),
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.IR db (1),
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.IR proc (3),
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.IR snap (6)
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.SH BUGS
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The snapshots take up about as much disk space
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as the processes they contain did memory.
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Compressing them when not in use is recommended,
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as is storing them on a rewritable disk.
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.PP
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.I Pid
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as a non-numeric string is unimplemented; it has to be a number.