SNAP(4) SNAP(4)
NAME
snap, snapfs - create and mount process snapshots
SYNOPSIS
snap [ -o file ] pid...
snapfs [ -a ] [ -m mtpt ] file...
DESCRIPTION
Snap and snapfs allow one to save and restore (static) pro-
cess images, usually for debugging on a different machine or
at a different time.
Snap writes a snapshot (see snap(6)) of the named processes
to file (default standard output). Both memory and text
images are saved.
Snapfs is a file server that recreates the /proc directories
for the processes in the snapshot. By default, it mounts
the new directories into /proc before the current entries.
The -m option can be used to specify an alternate mount-
point, while -a will cause it to mount the new directories
after the current entries.
EXAMPLE
Suppose page has hung viewing Postscript on your terminal,
but the author is gone for the rest of the month and you
want to make sure the process is still around for debugging
on his return. You can save the errant processes with
snap -o page.snap `{psu | awk '$NF ~ /page|gs/ {print $2}'}
When the author returns, he can add the process images to
his name space by running
snapfs page.snap
and then use a conventional debugger to debug them.
SOURCE
/sys/src/cmd/snap
SEE ALSO
acid(1), db(1), proc(3), snap(6)
BUGS
The snapshots take up about as much disk space as the pro-
cesses they contain did memory. Compressing them when not
in use is recommended, as is storing them on a rewritable
disk.
Page 1 Plan 9 (printed 12/22/24)
SNAP(4) SNAP(4)
Pid as a non-numeric string is unimplemented; it has to be a
number.
Page 2 Plan 9 (printed 12/22/24)