Re: Help with chpst -e

[Andras Korn <korn-supervise@elan.rulez.org>]

On Mon, Apr 14, 2008 at 10:00:15PM +0100, Robin Bowes wrote:

>
> This script:
>
> 1. Uses chpst -e to set some vars from ./env (if ./env exists)
> 2. Uses the name of the service dir as the log user and log dir, if
>    the are not set in ./env
> 3. Creates the log dir, if it does not exist, and sets permissions

Here is what I use as a generic log/run script, fwiw:

---8<---
#!/bin/sh
SVNAME=$(basename $(dirname $(readlink -f .)))
LOGDIR=/var/log/sv/$SVNAME
LOGUSER=log
SIZE=50000
NUM=15
POSTPROC="gzip -9"
SVLOGDOPTS="-t"

[ -r /etc/default/svlogd ] && . /etc/default/svlogd
[ -r "/etc/default/$SVNAME" ] && . "/etc/default/$SVNAME"

mkdir -p $LOGDIR

chown $LOGUSER $LOGDIR $LOGDIR/lock $LOGDIR/state $LOGDIR/current 2>/dev/null
chmod 1700 $LOGDIR

cd $LOGDIR || exit 1
if [ ! -f config ]; then
	cat <<EOF >config
s$SIZE
n$NUM
!tryto -pP $POSTPROC
EOF
fi

exec chpst -u$LOGUSER svlogd $SVLOGDOPTS $LOGDIR
--->8---

This is more "Debianish" in that it gets the configuration from
/etc/default/svlogd, possibly overridden by /etc/default/name-of-service.
These files can override the svlogd config as well (e.g. set a different
postprocessor or retention policy).

I keep /var/log/sv on a separate volume from /var/log because not everything
logs via svlogd and /var/log might be filled.

I went easy on the quoting because I know I don't use LOGDIRs with spaces in
them.

Log directories are sticky and 'config' is owned by root; thus, in the
unlikely event that svlogd were to be compromised, it still couldn't
overwrite its own configuration. Yay!

As for your script, some comments:

> #!/bin/sh
>
> # if we haven't already done so, check for ./env dir
> # if it exists, set some env vars
> if [ "$1" != "have-env" ]; then
>   if [ -d ./env ]; then
>     exec chpst -e ./env "$0" have-env
>   fi
> fi
>
> LOG_PARENT=/var/log
>
> # Get the service name
> logdir=`pwd`
> svcdir=${logdir%/log}
> SERVICE_NAME=${svcdir##*/}

Isn't this a bashism?

> # Set LOGUSER and LOGDIR to default values if not set in ./env
> : ${LOGUSER:=${LOG_PARENT}/${SERVICE_NAME}}
> : ${LOGDIR:=${LOG_PARENT}/${SERVICE_NAME}}

You could use LOGDIR=${LOGDIR:-$LOG_PARENT/$SERVICE_NAME} for no real
benefit. Setting LOGUSER to the name of a directory is probably a
copy-paste mistake, I guess? :)

> # Make sure the log dir exists
> if [ ! -e "${LOGDIR}" ]; then
>   mkdir -p "${LOGDIR}"
> fi

This fails if LOGDIR exists but is not a directory. (Of course, that
shouldn't happen.)

> # Set ownership & permissions on the log dir
> chown -R ${LOGUSER} "${LOGDIR}"

This gives ownership of the config file, if it exists, to svlogd. I don't
think that's good. 

Andras

-- 
                 Andras Korn <korn at chardonnay.math.bme.hu>
                 <http://chardonnay.math.bme.hu/~korn/>	QOTD:
         "Meow" ...splat... "Aarf" ...splat... (raining cats and dogs)