On Linux virtual machines, VMware supports
only crash-consistent backups, however application-consistent backups are
possible through the use of customer pre-freeze and post-thaw scripts.
Two methods are attempted sequentially when a
quiesced snapshot is requested of a Linux virtual machine:
Procedure
-
Using the
ioctl(2) mechanisms
FIFREEZE and
FITHAW built into the Linux
kernel.
This option is available in only with kernel
versions newer than 2.6.32 on Linux virtual machines running VMware Tools 5.x
or higher (vSphere 5.0 and later).
-
Using the
sync(2) system call.
The first method allows you define custom
scripts that get called by VMware Tools before and after quiesce. Here are two
commands that can be called from pre-freeze and post-freeze scripts:
# -f means freeze
fsfreeze -f /
# -u means unfreeze
fsfreeze -u /
The mount point used in the scripts (root in
the examples above) must be mounted with the
noatime option, meaning do
not update
inode access times on the
file system, for freeze and unfreeze to work.