The officially official Devuan Forum!

You are not logged in.

#1 2017-11-27 10:01:24

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

runit as a process supervisor

Having reading the message on DNG from Steve Litt about process supervisors :-

https://lists.dyne.org/lurker/message/2 … d3.en.html

I was inspired to investigate for myself. This is not a recipe on how to use runit as your init system, but some notes on using runit as a stage 2 process supervisor.

Of the supervisors mentioned by Steve, only runit was available in the jessie repository so that is what I had a look at.

The set up on ascii is slightly different from jessie. On jessie when installed it all ready for running as a process supervisor. On ascii there is a separate package to install to set up this supervisory role. It would appear that the ascii version is more ready to be run as a replacement init.

On jessie :-

apt-get install runit

on ascii

apt-get install runit runit-sysv

When running

ps uaxf

runsvdir can be seen with space "....." for displaying log messages,
although it is not actually supervising anything yet.

The ascii installation seems to be missing some of the documetation at :-

file:///usr/share/doc/runit/html/

in that the info on the separate programs is missing, although the index.html
page does give the link to the author's pages :-

http://smarden.org/runit/

Also on ascii the directory /etc/service is a link to /etc/runit/default.

Once runit is installed, then comes the job of setting up some daemons to be supervised. They are set up in sub-directories of /etc/sv and when everything is ready a link is set up in /etc/service to the sub-directory in /etc/sv. At this point runsvdir should notice and start running the daemon.

I wanted something simple to start with and went for the display manager. This is very simple, although there is some scope for fun as this can crash X while you are finishing the set-up, so it is good to know what you need to do to finish things. One difference from sysv init is that the daemon should not run in the background, but should remain connected to stdin/stdout. In this case, it means NOT using the "-d" switch to the display manager.

While on jessie I am using "slim" with lxde, on ascii I am using "lxdm" with lxde with some components of lxqt.

There needs to be a file called "run" to run the daemon. Is also possible to set up logging, using svlogd. This uses a sub-directory called log and its own "run" file. The supplied examples show logs being written under the log sub-directory, that is, within the /etc filesystem. I was not too happy with this and set up a separate directory in /var Presumably you could log in /var/log, but I avoided that in case there was any interaction with logrotate, as svlogd looks after its own logs.

These are the steps I took to set up lxdm under runit on ascii :-

mkdir -p /var/svlogd/lxdm
adduser --system log
chown -R log /var/svlogd

cd /etc/sv
mkdir -p lxdm/log

cd lxdm
cat << EOF > run
#!/bin/sh
exec 2>&1
exec /usr/sbin/lxdm
EOF

cd log
cat << EOF > run
#!/bin/sh
exec chpst -ulog svlogd -tt /var/svlogd/lxdm
EOF

cd ..
chmod a+x run log/run

cd /etc/service
update-rc.d lxdm disable
ln -s /etc/sv/lxdm .

This failed to stop X, but was all set up, so I rebooted and it all just worked.
Looking at the output from ps :-

ps uaxf

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
...
root      2398  0.0  0.0   4212  1076 ?        Ss   15:44   0:00 runsvdir -P /etc/service log: ....................................................................
root      2405  0.0  0.0   4060   672 ?        Ss   15:44   0:00  \_ runsv lxdm
log       2406  0.0  0.0   4204   684 ?        S    15:44   0:00      \_ svlogd -tt /var/svlogd/lxdm
root      2407  0.0  0.0  43976  3604 ?        S    15:44   0:00      \_ /usr/sbin/lxdm-binary
root      2412  0.7  0.8 389104 71868 tty7     Ssl+ 15:44   0:27          \_ /usr/lib/xorg/Xorg :0 vt07 -nolisten tcp -novtswitch -auth /var/run/lxdm/lxdm-:0.auth
root      2425  0.0  0.0  49976  3256 ?        S    15:44   0:00          \_ /usr/lib/lxdm/lxdm-session
xxxxxx    2506  0.0  0.1 352720 13280 ?        Ssl  15:44   0:00              \_ /usr/bin/lxsession -s LXDE -e LXDE
xxxxxx    2559  0.0  0.0  11076   332 ?        Ss   15:44   0:00                  \_ /usr/bin/ssh-agent /usr/bin/startlxde
xxxxxx    2568  0.0  0.2 196632 16580 ?        S    15:44   0:01                  \_ openbox --config-file /home/xxxxxx/.config/openbox/lxde-rc.xml
xxxxxx    2573  0.1  0.3 910200 25920 ?        Sl   15:44   0:04                  \_ lxpanel --profile LXDE
xxxxxx    2788  0.0  0.0  36816  4668 ?        S    15:45   0:00                  |   \_ urxvt
xxxxxx    2789  0.0  0.0  39236  2636 ?        S    15:45   0:00                  |   |   \_ urxvt
xxxxxx    2790  0.0  0.0  18396  3468 pts/0    Ss   15:45   0:00                  |   |   \_ bash
xxxxxx    3668  0.5  0.5 327340 47736 pts/0    Sl   16:38   0:03                  |   |       \_ emacs runit
xxxxxx    3820  0.0  0.0  17656  2068 pts/0    R+   16:48   0:00                  |   |       \_ ps uaxf
xxxxxx    2990  0.0  0.4 374260 39964 ?        Sl   15:59   0:01                  |   \_ claws-mail
xxxxxx    3306  3.8  3.1 857764 252200 ?       Sl   16:21   1:02                  |   \_ palemoon
xxxxxx    2574  0.0  0.5 602248 47304 ?        S    15:44   0:00                  \_ spacefm --desktop

The log file, /var/svlogd/lxdm/current, is empty, unlike my slim set-up under jessie, where the log file has output from Xorg as it starts up.

The set-up for slim on jessie is the same, simply replacing the word "lxdm" with "slim" everywhere.

Offline

#2 2017-11-27 11:02:40

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

Postfix

Running the display manager under runit was very straightforward. I also tried something more complex. As a domestic user I use an mail provider, GMX in my case. However, some system messages are generated locally for delivery to root. Although I recall that exim had been installed, I had earlier experience with postfix, so I had installed that instead and configured it for my requirements and it was working well. This was obviously a prime target for trying out under runit!

Looking at /etc/init.d/postfix I found nearly 1000 lines of impenetrable script. Whereas, I thought that the actual command to start postfix was :-

postfix start

and the actual daemon which is left running is "/usr/lib/postfix/master -w".

There is an example "run" file in the documentation and I tried it


#!/bin/sh
exec 1>&2
 
daemon_directory=/usr/lib/postfix \
command_directory=/usr/sbin \
config_directory=/etc/postfix \
queue_directory=/var/spool/postfix \
mail_owner=postfix \
setgid_group=postdrop \
  /etc/postfix/postfix-script check || exit 1

exec /usr/lib/postfix/master

This did not work well. It appeared to be checking every single file on the system and spotting that most were not owned by postfix! It also failed to run the daemon.

After some fiddling around I decided to try and keep it simple. Since "postfix start" does actually work, why not use it? Well it finishes and returns, which is not how runit works. I therefore set up a simple kludge, /etc/sv/postfix/run :-

#!/bin/sh
exec 1>&2

/usr/sbin/postfix start
while /usr/sbin/postfix status
do sleep 300
done

This does actually work! It also puts out a timestamp every 5 minutes in the log file.

I was not sure how things would work at shutdown, so I also set up a "finish" file. This is described as being executed if "run" stops.
/etc/sv/postfix/finish

#!/bin/sh
echo "calling /etc/sv/postfix/finish"
/usr/sbin/postfix stop

My hope is that if things are not shutdown properly, then this would tidy it all up! What I see in /var/log/mail.info is that the "master" daemon reports

postfix/master[2916]: terminating on signal 15
postfix/postfix-script[4443]: fatal: the Postfix mail system is not running

I think that the second line is saying that it can't stop as it isn't running.
Postfix does its own logging via syslog.

This simple set up seems to work ok, although not really in the spirit of runit!

Geoff

Offline

#3 2017-11-27 20:10:57

fungus
Member
From: Any witch way
Registered: 2017-07-12
Posts: 497  
Website

Re: runit as a process supervisor

This is too good of a contribution to get passed by:
https://sysdfree.wordpress.com/162

If you have any objections or want to make additions or edit please let me know.

Offline

#4 2017-11-27 20:37:25

shevy
Member
Registered: 2017-08-16
Posts: 8  

Re: runit as a process supervisor

Perhaps it could be polished up a little and then put onto a wiki if others want to follow up?

Admittedly I do not even know half of what has been written here so far. :-)

Offline

#5 2017-11-28 09:27:14

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

fungus wrote:

If you have any objections or want to make additions or edit please let me know.

I am delighted that you find it useful. You are most welcome to use it.

Geoff

Offline

#6 2017-12-04 15:04:17

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

Postfix and shutdown

There is some further documentation on runit at Gentoo :-

https://wiki.gentoo.org/wiki/Runit

including some example run scripts to be found at :-

https://gitlab.com/flussence/runit-scripts

thus they offer a postfix run file :-

https://gitlab.com/flussence/runit-scri … ostfix/run

I added in -d and corrected the paths. This does seem to work, although I notice that the sub-processes also have the -d flag.

#!/bin/sh -eu
/usr/sbin/postfix check
exec /usr/lib/postfix/master -d

Although "master" is in itself a process supervisor which looks after the various postfix programs. I think that this leads into questions that have been rising in my mind about shutdown. It is not very clear from the documentation how shutdown works if you only use runit as a process supervisor. As far as I can see the shutdown mechanism would use stage 3 of runit, if you were using runit as init. (As a supervisor, it is only stage 2).

With the run file running "master" directly (with the -d flag), as above, then on shutdown, /var/log/mail.info reports

postfix/master[2795]: fatal: master_sigdeath: kill process group: No such process
postfix/postfix-script[4380]: fatal: the Postfix mail system is not running

I think that the first line is "master" receiving a signal to stop. From /var/log/syslog I can sees that at shutdown ntpd (which is not under runit) exiting on signal 15 (TERM), so I would guess that that is what "master" has received. The second line above is probably from "finish", which is being executed after "run" finishes and is therefore correct! The man page for "shutdown" says that "All processes are first notified that the system is going down by the signal SIGTERM." I have assumed that any daemons run by SysV init would have their "K" scripts in /etc/rc0.d run at shutdown, although I can't currently find the documentation on that!

As the couple of daemons that I am trying under runit are not part of the SysV init, I assume that they just receive SIGTERM.

I am wondering whether the answer is to set up runit's stage 3 and somehow trigger it at shutdown, early enough that the daemons get the signal before they get a SIGTERM from elsewhere. The sample stage 3 file for Debian Sarge looks like this :-

#!/bin/sh
exec 2>&1

PATH=/command:/sbin:/bin:/usr/sbin:/usr/bin

LAST=0
test -x /etc/runit/reboot && LAST=6

echo 'Waiting for services to stop...'
sv -w196 force-stop /etc/service/*
sv exit /etc/service/*

echo 'Shutdown...'
/etc/init.d/rc $LAST

Since runit is not in charge, presumably running /etc/init.d/rc $LAST can be commented out. I also removed /command from the path.
Maybe, this stage 3 file could be triggered as K010runit in /etc/rc[06].d to get these daemons to stop cleanly.

cd /etc/rc0.d
ln -s /etc/runit/3 K010runit3
cd /etc/rc6.d
ln -s /etc/runit/3 K010runit3

Also I looked at whether it is possible have runsv catch the SIGTERM and handle it more gracefully. The man page for runsv tells how to customise control signals, so that for SIGTERM :-

/etc/sv/postfix/control/t could contain :-

#!/bin/sh
echo We have SIGTERM for postfix
/usr/sbin/postfix stop

so this should run for "terminate" and should also pick up the control signals for "down" and "exit", according to the man page for runsv.

This does run and appear in /var/svlog/postfix/current when I give the command

sv stop postfix

I reverted the postfix "run" file to the earlier one which uses the "postfix start" command and
with stage 3 being called from rc0.d and with control/t set up, then on shutdown I can see in /var/log/syslog :-

Dec  4 10:49:58 fluorine shutdown[4884]: shutting down for system halt
Dec  4 10:49:58 fluorine init: Switching to runlevel: 0
Dec  4 10:49:59 fluorine avahi-daemon[2600]: Got SIGTERM, quitting.
Dec  4 10:49:59 fluorine avahi-daemon[2600]: Leaving mDNS multicast group on interface xenbr0.IPv6 with address fe...
Dec  4 10:49:59 fluorine avahi-daemon[2600]: Leaving mDNS multicast group on interface xenbr0.IPv4 with address 19...
Dec  4 10:49:59 fluorine avahi-daemon[2600]: avahi-daemon 0.6.31 exiting.
Dec  4 10:50:00 fluorine postfix/master[2924]: terminating on signal 15
Dec  4 10:50:00 fluorine ntpd[2466]: ntpd exiting on signal 15
Dec  4 10:50:00 fluorine postfix/postfix-script[5281]: fatal: the Postfix mail system is not running
Dec  4 10:50:00 fluorine postfix/postfix-script[5289]: fatal: the Postfix mail system is not running
Dec  4 10:50:01 fluorine acpid: exiting
Dec  4 10:50:03 fluorine rsyslogd: [origin software="rsyslogd" swVersion="8.4.2" x-pid="2166" x-info="http://www.rsyslog.com"] exiting on signal 15.

I think that the 2 fatal messages are from "finish" and control/t being called after "master" has alread received SIGTERM, although the echo messages are not appearing in /var/svlogd/postfix/current, maybe svlogd has already been shutdown!

I can see that before I started trying runit and with postfix being started from SysV init, that on shutdown /var/log/mail.info reports :-

Nov 11 12:23:20 fluorine postfix/master[2909]: terminating on signal 15

So the set up with "runit" seems to produce more or less the same result as with SysV init. Setting up to run stage 3 from rc0.d and also setting up control/t does not appear to have any real effect on shutdown.

Geoff

Offline

#7 2017-12-04 15:13:32

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

The actual file set up in /etc/sv/postfix looks like this :-

# find /etc/sv/postfix/ -name '*' -ls
651625    4 drwxr-xr-x   5 root     root         4096 Dec  3 17:41 /etc/sv/postfix/
652292    4 -rwxr-xr-x   1 root     root           71 Nov 24 14:31 /etc/sv/postfix/finish
652288    4 -rwxr-xr-x   1 root     root          121 Dec  3 17:41 /etc/sv/postfix/run
656409    4 drwxr-xr-x   2 root     root         4096 Dec  3 17:04 /etc/sv/postfix/control
661485    4 -rwxr-xr-x   1 root     root           66 Dec  3 17:04 /etc/sv/postfix/control/t
652295    4 drwxr-xr-x   3 root     root         4096 Dec  1 16:41 /etc/sv/postfix/log
661408    4 -rwxr-xr-x   1 root     root           58 Dec  1 16:38 /etc/sv/postfix/log/run
661426    4 drwx------   2 root     root         4096 Dec  4 13:48 /etc/sv/postfix/log/supervise
661458    0 -rw-------   1 root     root            0 Dec  1 16:41 /etc/sv/postfix/log/supervise/lock
661461    4 -rw-r--r--   1 root     root           20 Dec  4 13:48 /etc/sv/postfix/log/supervise/status
661477    0 prw-------   1 root     root            0 Dec  1 16:41 /etc/sv/postfix/log/supervise/ok
661728    4 -rw-r--r--   1 root     root            4 Dec  4 13:48 /etc/sv/postfix/log/supervise/stat
652424    4 -rw-r--r--   1 root     root            5 Dec  4 13:48 /etc/sv/postfix/log/supervise/pid
652426    0 prw-------   1 root     root            0 Dec  1 16:41 /etc/sv/postfix/log/supervise/control
652309    4 drwx------   2 root     root         4096 Dec  4 13:48 /etc/sv/postfix/supervise
654580    0 -rw-------   1 root     root            0 Nov 23 11:20 /etc/sv/postfix/supervise/lock
661489    4 -rw-r--r--   1 root     root           20 Dec  4 13:48 /etc/sv/postfix/supervise/status
661277    0 prw-------   1 root     root            0 Nov 23 11:20 /etc/sv/postfix/supervise/ok
661390    4 -rw-r--r--   1 root     root            4 Dec  4 13:48 /etc/sv/postfix/supervise/stat
661388    4 -rw-r--r--   1 root     root            5 Dec  4 13:48 /etc/sv/postfix/supervise/pid
656413    0 prw-------   1 root     root            0 Dec  3 17:17 /etc/sv/postfix/supervise/control

The supervise sub-directories are automatically set up by runsv.

Offline

#8 2017-12-07 09:57:39

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

I spotted another method of hanging for a daemon (rpc.nfsd) that detaches (in the Gentoo info).
The README file for the rpc.nfsd "run" says :-
   

"rpc.nfsd is a "fake" service implemented using lock-wedging. Doing it this way allows sv stop rpc.nfsd to work, by stopping it in the finish script."

After it has started the daemon, which detaches, the run file then does this :-

exec chpst -L supervise/runlock chpst -l supervise/runlock true

The change process state program (chpst) uses the -L switch to open the file supervise/runlock for writing, and obtain an exclusive lock on it. It then runs another copy of chpst which similarly gets a lock on the same file and then runs and returns "true".
The difference is that -L will fail immediately if it cannot get the lock, while -l will wait until it can get the lock. This line will therefore hang until it gets "sv stop postfix", when it will terminate true so that "finish" will be executed, which is set up to actually stop postfix. This does work as described, once the control/t file was moved out of the way, which was by-passing killing off the "run" process. The normal shutdown proceedure continues as before.

The set up is now fairly simple as it is only necessary to set up "run" & "finish" along with the logging.

cd /etc/sv/postfix
cat << EOF > run
#!/bin/sh
exec 2>&1
echo "executing /etc/sv/postfix/run"
/usr/sbin/postfix start
exec chpst -L supervise/runlock chpst -l supervise/runlock true
EOF

cat << EOF > finish
#!/bin/sh
exec 2>&1
echo "calling /etc/sv/postfix/finish"
/usr/sbin/postfix stop
EOF

mkdir log
cat << EOF > log/run
exec chpst -ulog svlogd -tt /var/svlogd/postfix
EOF

chmod a+x run finish log/run

the part of the output of ps uaxf relating to the postfix daemon looks like this :-

root      2767  0.0  0.0   4100   696 ?        Ss   09:02   0:00  \_ runsv postfix
log       2768  0.0  0.0   4244   708 ?        S    09:02   0:00      \_ svlogd -tt /var/svlogd/postfix
root      2771  0.0  0.0   4104   652 ?        S    09:02   0:00      \_ chpst -l supervise/runlock true
root      2903  0.0  0.0  36168  3152 ?        Ss   09:02   0:00 /usr/lib/postfix/master -w
postfix   2904  0.0  0.0  38232  3884 ?        S    09:02   0:00  \_ pickup -l -t unix -u -c
postfix   2905  0.0  0.0  38280  3936 ?        S    09:02   0:00  \_ qmgr -l -t unix -u

Geoff

Offline

#9 2017-12-11 10:46:12

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

Current state

across 2 machines, the following are running under runit :-

slim
lxdm
autofs
bluetoothd
wicd
postfix

For most of them it is simply the case of setting up a run file containing the command along with the flag to stop it from running as a daemon, but remain attached to stdin/stdout. With a few (lxdm) it is rather the case that you leave out the flag that causes it to become a daemon. It is probably a good idea to set up logging for most of them. It is only slightly more complex when the program really does want to run as a daemon, such as postfix.

There is the question of why the SysV init scripts are so complex. I think that these have evolved this way as they check that everything has been set up correctly and where possible put things in place that should be there. It is understandable that a general purpose distribution will want everything to just work out of the box. The price of this is perhaps that the mechanism becomes more complex. One of the complexities seems to be the setting up of a PID file. I think that this is necessary so that init is able to control the service, whereas this is probably not necessary under runit.

The services which I have set up do seem to be simpler, but it may be that they do actually work because they were originally set up under SysV init, which sorted out any problems!

If you are developing a new service or have one which is not set up for SysV init, then it may be easier to get it running under runit.

Geoff

Offline

#10 2017-12-16 16:04:30

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

Postgresql


The next service to try was postgresql. This proved to be a bit more complex, in that there was more to set up.
The command line according to the ps command was :-

/usr/lib/postgresql/9.4/bin/postgres -D /var/lib/postgresql/9.4/main -c config_file=/etc/postgresql/9.4/main/postgresql.conf

Logging was set up and then on putting this command into the run file it failed to run. The log file reported that postgres must not be run as root. "chpst" was then used to set the user and group to postgres:postgres. This then failed as it could not read the ssl certificate. "chpst" allows for a number of groups to be set so using postgres:postgres:ssl-cert seems to work, although postgres is already in the ssl-group in /etc/group! The next problem was that it needed the socket directory to be created in /var/run, which, as it is a tmpfs, disappears on a re-boot. It was also clear that the stats sub-directory also needed to be recreated. This can be done with install, to set up permissions and ownership in one command.

This then seems to work, but there are a number of directories involved and these may change with versions, indeed the version number is included in several of the directories. It therefore seemed reasonable to make these easy to configure. There is some documentation on clusters of databases, but I am only running one. It may be that the one database is called "main" by default and that that part of the path names should also be easy to configure.

The currently working set up is like this :-

mkdir /etc/sv/postgresql
cd /etc/sv/postgresql

cat << EOF > run
#!/bin/sh -eu
exec 2>&1

VERSION="9.4"

PGBINROOT="/usr/lib/postgresql"
RUNROOT="/var/run/postgresql"
DATAROOT="/var/lib/postgresql"
CONFROOT="/etc/postgresql"

BINFILE="${PGBINROOT}/${VERSION}/bin/postgres"
STATDIR="${RUNROOT}/${VERSION}-main.pg_stat_tmp"
DATAFILE="${DATAROOT}/${VERSION}/main"
CONFFILE="${CONFROOT}/${VERSION}/main/postgresql.conf"

# create socket and stats directories

install -d -m 2775 -o postgres -g postgres ${RUNROOT} ${STATDIR}

exec chpst -u postgres:postgres:ssl-cert ${BINFILE} -D ${DATAFILE} -c config_file=${CONFFILE}
EOF

mkdir log
cat << EOF > log/run
exec chpst -ulog svlogd -tt /var/svlogd/postgresql
EOF

chmod a+x run log/run
mkdir /var/svlogd/postgresql
chown log /var/svlogd/postgresql

cd /etc/service
/etc/init.d/postgresql stop
update-rc.d postgresql disable
ln -s /etc/sv/postgresql .

tail -f /var/svlogd/postgresql/current

Once you are happy that the log file is not producing lots of errors you can ^C out of it!

Geoff

Offline

#11 2017-12-17 15:34:17

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

Package upgrades

I was wondering about package upgrades as it appears that many services are automatically stopped before an upgrade and restarted afterwards, or possibly simply restarted after the upgrade. To have a look at how this worked I had a look through a ".deb" file. I copied one over to somewhere safe :-

cp /var/cache/apt/archives/apache2_2.4.10-10+deb8u11_amd64.deb .

and then had a look with spacefm/Xarchiver, extracting the control.tar file into my safe area. In the "postinst" file near the end is the code fragment :-

# Automatically added by dh_installinit
if [ -x "/etc/init.d/apache2" ]; then
	update-rc.d apache2 defaults 91 09 >/dev/null
	if [ -n "$2" ]; then
		_dh_action=restart
	else
		_dh_action=start
	fi
	invoke-rc.d apache2 $_dh_action || true
fi

Indeed, prerm and postrm also use invoke-rc.d and update-rc.d to stop apache and then remove the init.d links.
Interestingly, only postrm makes reference to systemd.

I suspect that the quick workaround is to do an apt-get upgrade and stop it when it asks. You would then inspect the packages to be upgraded and if you spot any of the services you have under runit, you would stop them manually. Then you would actually do the upgrade and then you could restart the services! I'm not sure that is the best answer! Runit's "sv" program does understand init.d and can be linked to from /etc/init.d

http://smarden.org/runit/faq.html#lsb

So that might be a way to have your services handled safely, although I wonder whether any upgrades might want to overwrite the service's init.d script, which could lead to sv be overwritten!

Geoff

Offline

#12 2017-12-30 16:15:19

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

Postfix again

I was reviewing the setup for Postfix, and having a fiddle, when I discovered that I had misunderstood the flags to the "master" program. Under SysV init, master runs with "-w", which launches it as a daemon, but does not return until the daemon is running correctly. If you omit the "-w" flag then master runs in the foreground, which is what we want! The set up then becomes very simple. All that is needed is a simple run file and you may setup logging if you wish. The "echo" in the run file is reported through the logging mechanism.

cat << EOF > run
#!/bin/sh -eu
echo "executing /etc/sv/postfix/run"
/usr/sbin/postfix check
exec /usr/lib/postfix/master
EOF

The "-eu" flags cause the script to fail on any unchecked errors. There is no need for a finish script. "ps uaxf" then reports :-

root      2658  0.0  0.0   4100   688 ?        Ss   14:31   0:00  \_ runsv postfix
log       2662  0.0  0.0   4244  1240 ?        S    14:31   0:00      \_ svlogd -tt /var/svlogd/postfix
root      3697  0.0  0.0  36168  3820 ?        Ss   15:54   0:00      \_ /usr/lib/postfix/master
postfix   3810  0.0  0.0  38232  3724 ?        S    15:54   0:00          \_ pickup -l -t unix -u -c
postfix   3811  0.0  0.0  38280  3924 ?        S    15:54   0:00          \_ qmgr -l -t unix -u

Geoff

Offline

#13 2017-12-31 03:43:16

mckaygerhard
Member
Registered: 2017-04-21
Posts: 185  
Website

Re: runit as a process supervisor

hi to all, i already now that this trheath its about a runit issues, but maybe a strategy move can be support upstart, that was used nomadays in winbuntu..

yeah unmantained but the point it's  due it's excelent compatibility (no need of any change for usage alongside with sysvinit)

can be a strategy move to more distributions and non-linux OS found a cooperative way to stop the alienate systemd process

we must take in consideration the workload to manpowers in devuan, what happened when project grow so many more thant the amount of developer can support? will be good a little of cooperative help beetweent MANY and not litle distros

Offline

#14 2018-01-03 14:23:20

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

Apache2

Another interesting example is Apache. It seems that the way to start it is with "apache2ctl start" as that is the way to get the environment set-up correctly. This results in the daemon(s) running in the background. The "run" file should wait for the daemon(s) to stop. As apache produces a pid file, it is easy to find the top daemon. What we would like to do is "wait $PID". Unfortunately this does not work as $PID is not a child of mine! It is, however, possible to look at /proc/$PID :-
https://stackoverflow.com/questions/105 … -to-finish

while [[ ( -d /proc/$PID ) && ( -z `grep zombie /proc/$PID/status` ) ]]; do
    sleep 1
done

Although I got a syntactical error with this, so I ended up with this "run" file :-

#!/bin/sh -eu
exec 2>&1
echo "executing /etc/sv/apache2/run"

/usr/sbin/apache2ctl configtest
/usr/sbin/apache2ctl start

# allow time for the PID file to be written

n=0
until [ -s /var/run/apache2/apache2.pid ]
do
   if [ $n -gt 5 ]
   then
      echo "/var/run/apache2/apache2.pid not found after ${n}s.
      exit 1
   fi
   n=$(( $n + 1 ))
   sleep 1
done

read PID < /var/run/apache2/apache2.pid
echo "apache2 running as pid ${PID}."

# wait for the $PID to stop

while [ -d /proc/$PID ] && [ -z `grep zombie /proc/$PID/status` ]
do
    sleep 60
done

I also set up a "finish" file as stopping the "run" script would not stop apache.

#!/bin/sh
# exec 2&>1
echo "calling /etc/sv/apache2/finish"
/usr/sbin/apache2ctl stop

I had wondered whether I could use chpst to put a lock on /proc/$PID or one of the files in that directory and then have a second copy of chpst to wait to get a lock on that file, to avoid the looping, but I though that it was best to avoid playing with the procfs!

I wonder whether one should take a different course of action if the $PID becomes a zombie?

Geoff

Offline

#15 2018-01-03 16:05:41

mckaygerhard
Member
Registered: 2017-04-21
Posts: 185  
Website

Re: runit as a process supervisor

umm there's no easy to packager a specific way to find process for each daemon/service in the OS, a more generic way to find PID and top process must be found..

but in those days nothing its standard unless systemd! oughtch! oh no! what i said!

Offline

#16 2018-01-19 07:31:44

Customer Service Robot
Member
Registered: 2018-01-19
Posts: 1  

Re: runit as a process supervisor

I did a bit of investigation into this matter myself, but the solution I came up with is far from elegant. Let's start with where runit currently stands in the Debian/Devuan universe. Runit can be used as PID 1, but for booting and shutting down, it depends on three different init scripts that in turn depend on sysvinit:

Booting:

/etc/init.d/rcS - Executes the symlinks to the actual startup scripts located in /etc/rc.d/S##xxxxxx with option "start".
/etc/init.d/rmnologin - Removes the /etc/nologin file as the last step in the boot process, if DELAYLOGIN=yes.

Shutting down:

/etc/init.d/rc - Main runlevel control script.

If your end goal is to use runit along with sysvinit for booting and shutting down, this is not a problem. For simplicity, however, I wanted to use runit independent of anything else. Attempting to purge all sysvinit packages along with the initscripts package resulted in an unbootable system. To circumvent this problem, I manually compiled Void Linux's runit configs along with their executables for rebooting, shutting down, etc. This allowed the system to boot again. In my opinion, Void's implementation for runit is far superior to that of Devuan's. If Void's runit could be used for Devuan, there is one other package I would like to be able to remove: init-system-helpers. init-system-helpers, from the information I could find, is only useful for switching between sysvinit and systemd. I don't see how it's necessary if runit is being used as PID 1.

Last edited by Customer Service Robot (2018-01-19 07:32:21)

Offline

#17 2018-04-01 16:03:53

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

Upgrading from Jessie to Ascii

When I upgraded my Jessie machine to Ascii, runit did not start. It should be started by a line added at the end of /etc/inittab. The upgrade had removed the start-up script from where it was. The script is now to be found as /etc/runit/2. The end of /etc/inittab should thus now be :-

#-- runit begin
SV:123456:respawn:/etc/runit/2
#-- runit end

and runit will then carry on supervising the processes which you have set up.

Geoff

Offline

#18 2018-04-02 10:21:27

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

It was also necessary to update the run file for PostgreSQL so that it sets the version number correctly, now at 9.6.

Geoff

Offline

#19 2018-05-16 08:48:20

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

I was wanting to try replacing SysVinit with OpenRC. It appeared that the set up for runit under OpenRC was a little different. Therefore, the first thing to do was to back out of running stuff under runit. The easiest one for me to back out of as a test was bluetoothd.

cd /etc/service
rm bluetoothd

this has now stopped bluetoothd. It appears that in setting up the init links the command does not run if there is a conflicting set-up, so it is easiest to remove the links and then set them to the default.

cd /etc/init.d
update-rc.d bluetooth remove
update-rc.d bluetooth defaults

This has now re-instated the links in /etc/rc2.d etc.
The machine was rebooted and bluetoothd was running normally.

The next one to try was lxdm. I set up the links first and then stopped it under runit, as it may well crash X.

cd /etc/init.d
update-rc.d lxdm remove
update-rc.d lxdm defaults

I then logged out and switched to the console with <CTRL><ALT><F1> and logged in as root

cd /etc/service
rm lxdm
shutdown -r now

This then came back normally with lxdm running under init.
It was now clear to put the remaining services under init, which in the case of my laptop was autofs and wicd.

cd /etc/init.d
update-rc.d autofs remove
update-rc.d autofs defaults
update-rc.d wicd remove
update-rc.d wicd defaults

cd /etc/service
rm autofs wicd

and then reboot. (Although this reboot could probably have waited until after the following step.)

All the services are now running normally and runsvdir is still running but not doing anything!
I edited /etc/inittab and commented out the line at the end which was running runsvdir, thus :-

#runit-sysv maintscript -- BEGIN
#SV:123456:respawn:/etc/runit/2
#runit-sysv maintscript -- END

A reboot then left everything running in a normal state. I will report on OpenRC in another thread.

https://dev1galaxy.org/viewtopic.php?id=2072

Geoff

Last edited by Geoff 42 (2018-05-16 09:02:49)

Offline

#20 2018-05-19 16:18:31

Geoff 42
Member
Registered: 2016-12-15
Posts: 177  

Re: runit as a process supervisor

I am reporting my efforts to get Runit integrated with OpenRC in a separate thread :-

https://dev1galaxy.org/viewtopic.php?id=2078

Geoff

Offline

Board footer