Hi all.

I've been using a program 'daemon' on freebsd
(eg man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

--
Mike Scott
Harlow, England


--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: Scott family (2:250/1@fidonet)

Mike Scott <usenet.16@scottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name
and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

If you want the housekeeping but don’t need to match the interface, your other option is to write a unit file and install it as a proper
service. systemd will handle the housekeeping.

--
https://www.greenend.org.uk/rjk/

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: terraraq NNTP server (2:250/1@fidonet)

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott <usenet.16@scottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg
man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name
and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

If you want the housekeeping but don’t need to match the interface, your other option is to write a unit file and install it as a proper
service. systemd will handle the housekeeping.

Many thanks. It's odd, but 'man -k daemon' turned up nothing (mint
zara), nor did a web search (too many matches perhaps saying what
daemons do). But it does seem to be available to apt (sudo apt install
daemon)



--
Mike Scott
Harlow, England

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: Scott family (2:250/1@fidonet)

On 2025-09-04, Mike Scott wrote:

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott <usenet.16@scottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
[...]
I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name
and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html
[...]

Many thanks. It's odd, but 'man -k daemon' turned up nothing (mint
zara) [...]

That's not surprising -- the "entirety" of manpages aren't installed by default, just the ones relevant to those applications that are
installed.



--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

On Thu, 9/4/2025 5:22 AM, Dan Purgert wrote:

On 2025-09-04, Mike Scott wrote:

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott <usenet.16@scottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
[...]
I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name
and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html
[...]

Many thanks. It's odd, but 'man -k daemon' turned up nothing (mint
zara) [...]

That's not surprising -- the "entirety" of manpages aren't installed by default, just the ones relevant to those applications that are
installed.

# Some of this is material from the Notes file, that has been
# sitting there for eons. These are necessitated by religion issues.
# Various parts of this may appear to be unnecessary (on your particular distro).

sudo add-apt-repository universe # If these are already present, the software will tell you
sudo add-apt-repository multiverse
sudo apt-get update # On live media, this step may fail depending on how old the media is

apt search daemon | less # In the worst case, will return a lot of (local) results
# You don't need to be root, to search for stuff.

sudo apt install daemon # Will put the manual page on local disk
man daemon # Read the manual page.

sudo apt install synaptic # Package Manager
sudo synaptic # Run the Package Manager, search for Daemon
# Do "Properties" on the line you find. It will list
# the file manifest. This helps with packages where the
# executable has a different name than the package (gddrescue, executable is ddrescue).

There have been package websites, which list packages and hint they exist.
Teh Google does not always return such sites today.

A Google search such as

linux man listdir

should give a manual page as the first or second result.

This is for the benefit of new users. In some cases, even the Terminal is
hard to find, but that's a whole nother post.

Paul

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

On Thu, 4 Sep 2025 06:12:11 -0400, Paul wrote:

There have been package websites, which list packages and hint they
exist.

packages.debian.org being an obvious one for Debian.

--- MBSE BBS v1.1.1 (Linux-x86_64)
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On Thu, 4 Sep 2025 08:38:08 +0100, Mike Scott wrote:

It's odd, but 'man -k daemon' turned up nothing (mint zara) ...

Should have at least turned up the standard C library routine <https://manpages.debian.org/daemon(3)>.

Note the warning there about its behaviour, though.

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

Lawrence D’Oliveiro <ldo@nz.invalid> writes:

On Thu, 4 Sep 2025 08:38:08 +0100, Mike Scott wrote:

It's odd, but 'man -k daemon' turned up nothing (mint zara) ...

Should have at least turned up the standard C library routine <https://manpages.debian.org/daemon(3)>.

Only if manpages-dev is installed, which isn’t necessarily the case.

--
https://www.greenend.org.uk/rjk/

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: terraraq NNTP server (2:250/1@fidonet)

On Fri, 05 Sep 2025 08:16:20 +0100, Richard Kettlewell wrote:

Lawrence D’Oliveiro <ldo@nz.invalid> writes:

On Thu, 4 Sep 2025 08:38:08 +0100, Mike Scott wrote:

It's odd, but 'man -k daemon' turned up nothing (mint zara) ...

Should have at least turned up the standard C library routine
<https://manpages.debian.org/daemon(3)>.

Only if manpages-dev is installed, which isn’t necessarily the case.

Ah. True, but surely any self-respecting developer would have done
that. ;)

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott<usenet.16@sc

ottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg
man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name
and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

Sorry, back again.

I've been playing with this and there seems to be an important feature
missing on linux that's in the BSD version: how to do logfile rotation?

BSD offers:
-H Close output_file and re-open it when signal SIGHUP is
received,
for interoperability with newsyslog(1) and similar log
rotation /
archival mechanisms. If -o is not specified, this flag is
ignored.


But the linux version seems to just keep writing to the same file
whatever I try. The only workaround seems to be to kill both the daemon
and its child, move the log file, and restart them. Seems a bit clumsy.

Have I missed something?

Thanks.



--
Mike Scott
Harlow, England

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: Scott family (2:250/1@fidonet)

On Wed, 10 Sep 2025 09:01:15 +0100, Mike Scott wrote:

But the linux version seems to just keep writing to the same file
whatever I try.

Aren’t you supposed to do logging through syslog?

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

On 2025-09-10, Mike Scott wrote:

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott<usenet.16@sc

ottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg
man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name
and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

Sorry, back again.

I've been playing with this and there seems to be an important feature missing on linux that's in the BSD version: how to do logfile rotation?
[...]
Have I missed something?

logrotate(8) ?


--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

On 10/09/2025 09:42, Dan Purgert wrote:

On 2025-09-10, Mike Scott wrote:

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott<usenet.16@sc

ottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg
man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name
and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

Sorry, back again.

I've been playing with this and there seems to be an important feature
missing on linux that's in the BSD version: how to do logfile rotation?
[...]
Have I missed something?

logrotate(8) ?

Thanks for the reply, but no. That assumes the existence of the
mechanism missing AFAICS from this daemon.

And to answer ldo, this is for a web daemon that writes its own private
log file that needs archival copies kept; syslog is not appropriate.
I've been doing that using mv and sending the BSD daemon a sighup;
migration is being something of a chore.

Looks like I'll have to see about patching the daemon source code.



--
Mike Scott
Harlow, England

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: Scott family (2:250/1@fidonet)

On 2025-09-10, Mike Scott wrote:

On 10/09/2025 09:42, Dan Purgert wrote:

On 2025-09-10, Mike Scott wrote:

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott<usenet.16@sc

ottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg
man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name >>>> and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

Sorry, back again.

I've been playing with this and there seems to be an important feature
missing on linux that's in the BSD version: how to do logfile rotation?
[...]
Have I missed something?

logrotate(8) ?

Thanks for the reply, but no. That assumes the existence of the
mechanism missing AFAICS from this daemon.

I'm not sure what you mean here. "Logrotate" is a tool that exists.

Granted, the systems here have been getting in-place upgrades for the
last decade; maybe logrotate has since been replaced in 'clean' installs
(or it's not a default part of the installation and I've just completely forgotten that).

--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

In uk.comp.os.linux Dan Purgert <dan@djph.net> wrote:

On 2025-09-10, Mike Scott wrote:

On 10/09/2025 09:42, Dan Purgert wrote:

On 2025-09-10, Mike Scott wrote:

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott<usenet.16@sc

ottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg
man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name >>>> and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

Sorry, back again.

I've been playing with this and there seems to be an important feature >>> missing on linux that's in the BSD version: how to do logfile rotation? >>> [...]
Have I missed something?

logrotate(8) ?

Thanks for the reply, but no. That assumes the existence of the
mechanism missing AFAICS from this daemon.

I'm not sure what you mean here. "Logrotate" is a tool that exists.

Granted, the systems here have been getting in-place upgrades for the
last decade; maybe logrotate has since been replaced in 'clean' installs
(or it's not a default part of the installation and I've just completely forgotten that).

It sounds like the problem is that 'daemon' is never closing the output
file, so 'logrotate' is never able to process it. The -H flag is supposed
to tell daemon to close the file on SIGHUP so logrotate can swap it out, but
it doesn't exist in the Debian version.

This is the source to the FreeBSD version: https://github.com/freebsd/freebsd-src/tree/main/usr.sbin/daemon

- maybe the 'sighup' feature could be merged into the Debian version?

Theo

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: University of Cambridge, England (2:250/1@fidonet)

On 2025-09-10, Theo wrote:

In uk.comp.os.linux Dan Purgert <dan@djph.net> wrote:

On 2025-09-10, Mike Scott wrote:

On 10/09/2025 09:42, Dan Purgert wrote:

On 2025-09-10, Mike Scott wrote:

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott<usenet.16@sc

ottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg
man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name >> >>>> and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

Sorry, back again.

I've been playing with this and there seems to be an important feature >> >>> missing on linux that's in the BSD version: how to do logfile rotation? >> >>> [...]
Have I missed something?

logrotate(8) ?

Thanks for the reply, but no. That assumes the existence of the
mechanism missing AFAICS from this daemon.

I'm not sure what you mean here. "Logrotate" is a tool that exists.

Granted, the systems here have been getting in-place upgrades for the
last decade; maybe logrotate has since been replaced in 'clean' installs
(or it's not a default part of the installation and I've just completely
forgotten that).

It sounds like the problem is that 'daemon' is never closing the output
file, so 'logrotate' is never able to process it. The -H flag is supposed
to tell daemon to close the file on SIGHUP so logrotate can swap it
out, but it doesn't exist in the Debian version.

Oh, then you add 'copytruncate' to the rotate directives, and the
original log gets zeroed out when logrotate runs.


--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

On 10/09/2025 at 09:27, Lawrence D’Oliveiro wrote:

On Wed, 10 Sep 2025 09:01:15 +0100, Mike Scott wrote:

But the linux version seems to just keep writing to the same file
whatever I try.

Aren’t you supposed to do logging through syslog?

ITYF systemd doesn't use syslog - see journalctl.

Perhaps run the daemon via systemd, or install (r)syslog + logrotate


--
Chris Elvidge, England
MY HOMEWORK WAS NOT STOLEN BY A ONE-ARMED MAN
Bart Simpson on chalkboard in episode 1F11


--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

On 10/09/2025 10:37, Dan Purgert wrote:

I'm not sure what you mean here. "Logrotate" is a tool that exists.

logrotate assumes the target can close and re-open its log. Witness,
from the man page, a config file entry:

"/var/log/httpd/access.log" /var/log/httpd/error.log {
rotate 5
mail recipient@example.org
size 100k
sharedscripts
postrotate
/usr/bin/killall -HUP httpd
endscript
}

The point being the target does its own close and reopen, often, as
here, with a sighup.

If the target can't do this somehow, bets are off. All logrotate does is schedule things, and handle the renaming; it has no magic to close and
reopen someone else's file.

The 'daemon' program seems to have no way of cooperating with any
external (non-brute) force to achieve this.

--
Mike Scott
Harlow, England

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: Scott family (2:250/1@fidonet)

On 10/09/2025 11:08, Theo wrote:

It sounds like the problem is that 'daemon' is never closing the output
file, so 'logrotate' is never able to process it. The -H flag is supposed
to tell daemon to close the file on SIGHUP so logrotate can swap it out, but it doesn't exist in the Debian version.

Absolutely the problem.

I'm years out of practice with writing C, but it looks a manageable job
to add the necessary code. Might take me a while though.

This is the source to the FreeBSD version: https://github.com/freebsd/freebsd-src/tree/main/usr.sbin/daemon

- maybe the 'sighup' feature could be merged into the Debian version?

If I can do it, I'll see about getting the changes merged in to the
original.

Theo

--
Mike Scott
Harlow, England

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: Scott family (2:250/1@fidonet)

On 2025-09-10, Mike Scott wrote:

On 10/09/2025 10:37, Dan Purgert wrote:

I'm not sure what you mean here. "Logrotate" is a tool that exists.

logrotate assumes the target can close and re-open its log.

By default, sure; but there are options to deal with it.


copytruncate
Truncate the original log file to zero size in place after cre-
ating a copy, instead of moving the old log file and optionally
creating a new one. It can be used when some program cannot be
told to close its logfile and thus might continue writing (ap-
pending) to the previous log file forever. Note that there is a
very small time slice between copying the file and truncating
it, so some logging data might be lost. When this option is
used, the create option will have no effect, as the old log file
stays in place. The copytruncate option allows storing rotated
log files on the different devices using olddir directive. The
copytruncate option implies norenamecopy.




--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

On 10/09/2025 12:31, Dan Purgert wrote:

On 2025-09-10, Mike Scott wrote:

On 10/09/2025 10:37, Dan Purgert wrote:

I'm not sure what you mean here. "Logrotate" is a tool that exists.

logrotate assumes the target can close and re-open its log.

By default, sure; but there are options to deal with it.

copytruncate
Truncate the original log file to zero size in place after cre-
ating a copy, instead of moving the old log file and optionally
creating a new one. It can be used when some program cannot be
told to close its logfile and thus might continue writing (ap-
pending) to the previous log file forever. Note that there is a
very small time slice between copying the file and truncating
it, so some logging data might be lost. When this option is
used, the create option will have no effect, as the old log file
stays in place. The copytruncate option allows storing rotated
log files on the different devices using olddir directive. The
copytruncate option implies norenamecopy.

logrotate is a new one to me, and I didn't see this on a quick glance at
the man page; thanks for pointing it out. There's no freebsd equivalent
AFAIK, where newsyslog does the equivalent job.

I'm not sure about the potential data loss that's noted in the man page.
I dislike anything that can fail unexpectedly and lose data.

Anyway, I have made the alteration to the daemon program itself. My
version looks for SIGUSR2, which will close and reopen the log files
without any data loss.

Good to have a choice though, so thanks for the helpful reply.





--
Mike Scott
Harlow, England

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: Scott family (2:250/1@fidonet)

On Wed, 10 Sep 2025 12:04:48 +0100, Chris Elvidge wrote:

On 10/09/2025 at 09:27, Lawrence D’Oliveiro wrote:

On Wed, 10 Sep 2025 09:01:15 +0100, Mike Scott wrote:

But the linux version seems to just keep writing to the same file
whatever I try.

Aren’t you supposed to do logging through syslog?

ITYF systemd doesn't use syslog - see journalctl.

systemd myth number 20: systemd makes it impossible to run syslog <https://0pointer.de/blog/projects/the-biggest-myths.html>.

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

Mike Scott <usenet.16@scottsonline.org.uk.invalid> writes:

On 10/09/2025 09:42, Dan Purgert wrote:

On 2025-09-10, Mike Scott wrote:

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott<usenet.16@sc

ottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg
man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name >>>> and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

Sorry, back again.

I've been playing with this and there seems to be an important feature
missing on linux that's in the BSD version: how to do logfile rotation?
[...]
Have I missed something?

logrotate(8) ?

Thanks for the reply, but no. That assumes the existence of the
mechanism missing AFAICS from this daemon.

And to answer ldo, this is for a web daemon that writes its own
private log file that needs archival copies kept; syslog is not
appropriate. I've been doing that using mv and sending the BSD daemon
a sighup; migration is being something of a chore.

Looks like I'll have to see about patching the daemon source code.

I’m not quite clear on the requirement here. I think what you mean is:

* The daemon executable logs to stdout and/or stderr
* You want these logs saved to a file
* You want this file rotated (in the normal way for a logfile)
* You want to keep the data essentially indefinitely, or at least, for
longer than other syslog outputs.

I can see several options.

1) Change the daemon to log to the target file instead of stdout/stderr,
and either arrange for it to close and re-open the logfile when it
recieves SIGHUP, or just do the log rotate itself (which avoids
dealing with signal handlers).

2) Add a second program that reads from stdin and writes to the target
logfile, doing the log rotation itself. The daemon command line would
be a pipeline, e.g. daemon sh -c "executable 2>&1 | loghandler".

3) Log to syslog, either directly or via the daemon wrapper. syslog
daemons (e.g. rsyslogd) can select a specific program’s logs to an
individual file, and you can control the log rotation policy for that
file individually. The syslog daemon takes care of the close/re-open
dance.

--
https://www.greenend.org.uk/rjk/

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: terraraq NNTP server (2:250/1@fidonet)

On 11/09/2025 08:49, Richard Kettlewell wrote:

Mike Scott <usenet.16@scottsonline.org.uk.invalid> writes:

On 10/09/2025 09:42, Dan Purgert wrote:

On 2025-09-10, Mike Scott wrote:

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott<usenet.16@sc

ottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg
man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)

which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please?

If you want an (almost) identical interface then in Debian (and
presumably therefore also Ubuntu), there’s a command of the same name >>>>> and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

Sorry, back again.

I've been playing with this and there seems to be an important feature >>>> missing on linux that's in the BSD version: how to do logfile rotation? >>>> [...]
Have I missed something?

logrotate(8) ?

Thanks for the reply, but no. That assumes the existence of the
mechanism missing AFAICS from this daemon.

And to answer ldo, this is for a web daemon that writes its own
private log file that needs archival copies kept; syslog is not
appropriate. I've been doing that using mv and sending the BSD daemon
a sighup; migration is being something of a chore.

Looks like I'll have to see about patching the daemon source code.

I’m not quite clear on the requirement here. I think what you mean is:

* The daemon executable logs to stdout and/or stderr
* You want these logs saved to a file
* You want this file rotated (in the normal way for a logfile)
* You want to keep the data essentially indefinitely, or at least, for
longer than other syslog outputs.

I can see several options.

1) Change the daemon to log to the target file instead of stdout/stderr,
and either arrange for it to close and re-open the logfile when it
recieves SIGHUP, or just do the log rotate itself (which avoids
dealing with signal handlers).

2) Add a second program that reads from stdin and writes to the target
logfile, doing the log rotation itself. The daemon command line would
be a pipeline, e.g. daemon sh -c "executable 2>&1 | loghandler".

3) Log to syslog, either directly or via the daemon wrapper. syslog
daemons (e.g. rsyslogd) can select a specific program’s logs to an
individual file, and you can control the log rotation policy for that
file individually. The syslog daemon takes care of the close/re-open
dance.

The problem is fixed to my satisfaction, but to answer your query.

The target program runs unattended for extended periods. It writes a lot
of data to stdout and stderr. It is not of itself a daemon in the linux
sense, just a large chunk of perl code that normally runs at a terminal.
To make it a self-contained linux daemon would be a pain, and pointless duplication of code. At user-determined intervals, I need output to be directed to a fresh file.

On freebsd, I've been using a program called 'daemon'. This runs the
target program as a child process, intercepting its stdout and stderr
and writing their data to a suitable file; it also does the necessary detaching and other housekeeping operations on its behalf. Importantly, 'daemon' responds to a suitable signal by closing and reopening its
output. This provides a way of chopping up the target program's output
streams into files for archiving and further processing without stopping it.

The linux program of the same name does much the same - but lacks the
ability to close and reopen its output files. 'logrotate' can sort-of
work around this with a (small) risk of data loss for programs like
mine, that cannot handle rotation hygienically.

I've now modified the linux 'daemon' program to respond as the freebsd
one, and it can now close and reopen its output file(s) without risk of
data loss. So archiving now becomes a simple matter of "mv log.txt
log.old; kill -usr2 <daemon-pid>" which results in log.old with the data
to date, and a fresh log.txt being opened.

I've emailed the author to see if he's interested in rolling the
modification into the next release.

And yes, I suppose your suggestion #2 would have worked. But involving a
3rd program is messy, and I'd still be having cut code to tell it to do
the log rotation on request. Better to put that where it really belongs,
I think. But thanks for the idea.



--
Mike Scott
Harlow, England

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: Scott family (2:250/1@fidonet)

On 10/09/2025 at 20:32, Lawrence D’Oliveiro wrote:

On Wed, 10 Sep 2025 12:04:48 +0100, Chris Elvidge wrote:

On 10/09/2025 at 09:27, Lawrence D’Oliveiro wrote:

On Wed, 10 Sep 2025 09:01:15 +0100, Mike Scott wrote:

But the linux version seems to just keep writing to the same file
whatever I try.

Aren’t you supposed to do logging through syslog?

ITYF systemd doesn't use syslog - see journalctl.

systemd myth number 20: systemd makes it impossible to run syslog <https://0pointer.de/blog/projects/the-biggest-myths.html>.

I didn't say it couldn't, just that it didn't.


--
Chris Elvidge, England
ALL WORK AND NO PLAY MAKES BART A DULL BOY
Bart Simpson on chalkboard in episode 1F07


--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

On 11/09/2025 at 11:02, Mike Scott wrote:

On 11/09/2025 08:49, Richard Kettlewell wrote:

Mike Scott <usenet.16@scottsonline.org.uk.invalid> writes:

On 10/09/2025 09:42, Dan Purgert wrote:

On 2025-09-10, Mike Scott wrote:

On 04/09/2025 08:26, Richard Kettlewell wrote:

Mike Scott<usenet.16@sc

ottsonline.org.uk.invalid> writes:

I've been using a program 'daemon' on freebsd
(eg
man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpath=FreeBSD+14.3-RELEASE+and+Ports)


which will run arbitrary programs as daemons, handling all the
necessary "house-keeping" for them.

I can't find a ready-to-roll linux version - is there one please? >>>>>> If you want an (almost) identical interface then in Debian (and

presumably therefore also Ubuntu), there’s a command of the same name >>>>>> and similar behavior:

https://manpages.debian.org/trixie/daemon/daemon.1.en.html

Sorry, back again.

I've been playing with this and there seems to be an important feature >>>>> missing on linux that's in the BSD version: how to do logfile
rotation?
[...]
Have I missed something?

logrotate(8) ?

Thanks for the reply, but no. That assumes the existence of the
mechanism missing AFAICS from this daemon.

And to answer ldo, this is for a web daemon that writes its own
private log file that needs archival copies kept; syslog is not
appropriate. I've been doing that using mv and sending the BSD daemon
a sighup; migration is being something of a chore.

Looks like I'll have to see about patching the daemon source code.

I’m not quite clear on the requirement here. I think what you mean is:

* The daemon executable logs to stdout and/or stderr
* You want these logs saved to a file
* You want this file rotated (in the normal way for a logfile)
* You want to keep the data essentially indefinitely, or at least, for
longer than other syslog outputs.

I can see several options.

1) Change the daemon to log to the target file instead of stdout/stderr,
and either arrange for it to close and re-open the logfile when it
recieves SIGHUP, or just do the log rotate itself (which avoids
dealing with signal handlers).

2) Add a second program that reads from stdin and writes to the target
logfile, doing the log rotation itself. The daemon command line would
be a pipeline, e.g. daemon sh -c "executable 2>&1 | loghandler".

3) Log to syslog, either directly or via the daemon wrapper. syslog
daemons (e.g. rsyslogd) can select a specific program’s logs to an
individual file, and you can control the log rotation policy for that
file individually. The syslog daemon takes care of the close/re-open
dance.

The problem is fixed to my satisfaction, but to answer your query.

The target program runs unattended for extended periods. It writes a lot
of data to stdout and stderr. It is not of itself a daemon in the linux sense, just a large chunk of perl code that normally runs at a terminal.
To make it a self-contained linux daemon would be a pain, and pointless duplication of code. At user-determined intervals, I need output to be directed to a fresh file.

On freebsd, I've been using a program called 'daemon'. This runs the
target program as a child process, intercepting its stdout and stderr
and writing their data to a suitable file; it also does the necessary detaching and other housekeeping operations on its behalf. Importantly, 'daemon' responds to a suitable signal by closing and reopening its
output. This provides a way of chopping up the target program's output streams into files for archiving and further processing without stopping
it.

The linux program of the same name does much the same - but lacks the ability to close and reopen its output files. 'logrotate' can sort-of
work around this with a (small) risk of data loss for programs like
mine, that cannot handle rotation hygienically.

I've now modified the linux 'daemon' program to respond as the freebsd
one, and it can now close and reopen its output file(s) without risk of
data loss. So archiving now becomes a simple matter of "mv log.txt
log.old; kill -usr2 <daemon-pid>" which results in log.old with the data
to date, and a fresh log.txt being opened.

I've emailed the author to see if he's interested in rolling the modification into the next release.

And yes, I suppose your suggestion #2 would have worked. But involving a
3rd program is messy, and I'd still be having cut code to tell it to do
the log rotation on request. Better to put that where it really belongs,
I think. But thanks for the idea.

Have you seen 'daemonize' - seems to do what you want.


--
Chris Elvidge, England
ALL WORK AND NO PLAY MAKES BART A DULL BOY
Bart Simpson on chalkboard in episode 1F07


--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

Chris Elvidge <chris@internal.net> writes:

Lawrence D’Oliveiro wrote:

On Wed, 10 Sep 2025 12:04:48 +0100, Chris Elvidge wrote:

On 10/09/2025 at 09:27, Lawrence D’Oliveiro wrote:

On Wed, 10 Sep 2025 09:01:15 +0100, Mike Scott wrote:

But the linux version seems to just keep writing to the same file
whatever I try.

Aren’t you supposed to do logging through syslog?

ITYF systemd doesn't use syslog - see journalctl.

systemd myth number 20: systemd makes it impossible to run syslog
<https://0pointer.de/blog/projects/the-biggest-myths.html>.

I didn't say it couldn't, just that it didn't.

In the context of a question about “logging through syslog”, it _does_
use syslog. journald listens on /dev/log and the syslog(3) API works.

--
https://www.greenend.org.uk/rjk/

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: terraraq NNTP server (2:250/1@fidonet)

On Thu, 11 Sep 2025 11:02:30 +0100, Mike Scott wrote:

The target program runs unattended for extended periods. It writes a
lot of data to stdout and stderr. It is not of itself a daemon in
the linux sense, just a large chunk of perl code that normally runs
at a terminal. To make it a self-contained linux daemon would be a
pain, and pointless duplication of code.

It shouldn’t take much work to make it runnable as a daemon. Remember,
the distinction in *nix isn’t that great, anyway: look at common
existing service daemons, and you will see that lots of them will run
fine in non-daemon mode, specifically to ease debugging.

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: A noiseless patient Spider (2:250/1@fidonet)

On 11/09/2025 13:53, Chris Elvidge wrote:

Have you seen 'daemonize' - seems to do what you want.

I can't see anything in the man page for that, or its website, that
suggests it can close and reopen log files. It seems very similar to
'daemon'. But thanks for commenting.


--
Mike Scott
Harlow, England

--- MBSE BBS v1.1.1 (Linux-x86_64)
* Origin: Scott family (2:250/1@fidonet)