config: add silent mode

Accept -q as the short form of --quiet.
Suppress non-essential standard output if -q is given twice.
Treat log/silent in lvm.conf as equivalent to -qq.
Review all log_print messages and change some to
log_print_unless_silent.

When silent, the following commands still produce output:
dumpconfig, lvdisplay, lvmdiskscan, lvs, pvck, pvdisplay,
pvs, version, vgcfgrestore -l, vgdisplay, vgs.
[Needs checking.]

Non-essential messages are shifted from log level 4 to log level 5
for syslog and lvm2_log_fn purposes.

1 files changed, 6 insertions, 0 deletions

diff --git a/man/lvm.conf.5.in b/man/lvm.conf.5.in
index 47ee9f13..79044fcc 100644
--- a/man/lvm.conf.5.in
+++ b/man/lvm.conf.5.in
@@ -226,6 +226,12 @@ is invoked.  By default tools append messages to the log file.
 \fBverbose\fP \(em Default level (0-3) of messages sent to stdout or stderr.
 3 is the most verbose; 0 should produce the least output.
 .IP
+\fBsilent\fP \(em Set to 1 to suppress all non-essential tool output.
+When set, display and reporting tools will still write the requested
+device properties to standard output, but messages confirming that
+something was or wasn't changed will be reduced to the 'verbose' level
+and not appear unless -v is supplied.
+.IP
 \fBsyslog\fP \(em Set to 1 (the default) to send log messages through syslog.
 Turn off by setting to 0.  If you set to an integer greater than one,
 this is used - unvalidated - as the facility.  The default is LOG_USER.