Comment by xerxes901

11 hours ago

Put a script in /etc/systemd/system-generators/ that does something like

  if grep "logging = syslog" /etc/stupid-service/stupid-service.conf >/dev/null; then
    printf "[Unit]\nAfter=rsyslogd.service\n" > "$1/stupid-service.d/10-syslog-dep.conf";
  fi;

> It's pretty basic and straightforward

Postgres config supports line continuations, so the OpenRC service file you quoted is buggy; it could potentially match a file just because some other option contained a multi-line value that had the string "log_destination = syslog" in it.

The whole philosophy of systemd is to move away from these kinds of "simple" and "mostly working" pile-of-shell-script systems to actually-unconditionally-correct configuration that doesn't come with bonus text processing surprises.

1 comment

xerxes901

simoncion 9 hours ago

> Postgres config supports line continuations, so the OpenRC service file you quoted is buggy; ...

Where's that documented?

I tried the obvious things followed by a config reload. Here are the results (the 'log_destination' parameter is on line 482 of the config file):

  log_destination = \
   'stderr'
  
  LOG:  received SIGHUP, reloading configuration files
  LOG:  syntax error in file "/etc/postgresql-18/postgresql.conf" line 482, near token "\"
  LOG:  syntax error in file "/etc/postgresql-18/postgresql.conf" line 483, near token "'stderr'"
  LOG:  configuration file "/etc/postgresql-18/postgresql.conf" contains errors; no changes were applied
  

  log_destination = 'std
  err'
  
  LOG:  received SIGHUP, reloading configuration files
  LOG:  syntax error in file "/etc/postgresql-18/postgresql.conf" line 482, near token "'"
  LOG:  syntax error in file "/etc/postgresql-18/postgresql.conf" line 483, near token "'"
  LOG:  configuration file "/etc/postgresql-18/postgresql.conf" contains errors; no changes were applied

  log_destination = 'std\
  err'
  
  LOG:  received SIGHUP, reloading configuration files
  LOG:  syntax error in file "/etc/postgresql-18/postgresql.conf" line 482, near token "'"
  LOG:  syntax error in file "/etc/postgresql-18/postgresql.conf" line 483, near token "'"
  LOG:  configuration file "/etc/postgresql-18/postgresql.conf" contains errors; no changes were applied

  log_destination = 'stderr'
  
  LOG:  received SIGHUP, reloading configuration files
  <No additional output is produced because 'stderr' is the default>
  
  #log_destination = 'stderr'
  
  LOG:  received SIGHUP, reloading configuration files
  LOG:  parameter "log_destination" removed from configuration file, reset to default

What's the line continuation character for 'postgresql.conf'? Are you certain that you're not getting 'postgresql.conf' confused with 'pg_hba.conf'? That file is documented to support line continuations: [0]

  The general format of the pg_hba.conf file is a set of records, one per line. Blank lines are ignored, as is any text after the # comment character. A record can be continued onto the next line by ending the line with a backslash. (Backslashes are not special except at the end of a line.)

> The whole philosophy of systemd is to move ... to actually-unconditionally-correct configuration that doesn't come with bonus text processing surprises.

That's truly a lovely and laudable goal. In this system, how does you propose one processes a flat text config file with a mix of 'K = V' and 'K V' settings without doing ordinary, boring text processing? Do you propose that one waits until "systemd-configd" gets created and every daemon of any importance is updated to put its config in there instead of in flat files? If so, has there been any notable progress on this in the last ~fifteen years?

> Put a script in /etc/systemd/system-generators/...

Thanks for finally answering my question. Is the way to conditionally update service dependencies really to dump text files in magic locations? Is there no 'systemctl' (or similar) command that allows one to manipulate dependencies for a specific service that one can call from a generator?

[0] <https://www.postgresql.org/docs/17/auth-pg-hba-conf.html>