X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=man%2Fdaemon.xml;h=d7cf0023634c8df943c1382b1c84ac784dc93b77;hp=105826ac6b2dbbb4c289052be8126a889593e5b2;hb=8c63bf4ab0d826148fa86e0b56b3498eff4a69b0;hpb=5486855f7d9748684633a96bf646d29080d5a28d diff --git a/man/daemon.xml b/man/daemon.xml index 105826ac6..d7cf00236 100644 --- a/man/daemon.xml +++ b/man/daemon.xml @@ -74,8 +74,8 @@ Close all open file - descriptors except STDIN, STDOUT, - STDERR (i.e. the first three file + descriptors except standard input, output, + and error (i.e. the first three file descriptors 0, 1, 2). This ensures that no accidentally passed file descriptor stays around in the daemon @@ -128,8 +128,8 @@ In the daemon process, connect /dev/null - to STDIN, STDOUT, - STDERR. + to standard input, output, and error. + In the daemon process, reset the umask to 0, so that the file @@ -149,7 +149,7 @@ write the daemon PID (as returned by getpid()) to a PID file, for example - /var/run/foobar.pid + /run/foobar.pid (for a hypothetical daemon "foobar") to ensure that the daemon cannot be started more than once. This must be @@ -158,9 +158,7 @@ it is verified at the same time that the PID previously stored in the PID file no longer exists or belongs to a - foreign process. Commonly, some kind of - file locking is employed to implement - this logic. + foreign process. In the daemon process, drop privileges, if possible and @@ -223,15 +221,16 @@ service. Note that new-style init systems - guarantee execution of daemon processes in - a clean process context: it is guaranteed that + guarantee execution of daemon processes in a + clean process context: it is guaranteed that the environment block is sanitized, that the signal handlers and mask is reset and that no left-over file descriptors are passed. Daemons - will be executed in their own session, and - STDIN/STDOUT/STDERR connected to + will be executed in their own session, with + standard input/output/error connected to /dev/null unless - otherwise configured. The umask is reset. + otherwise configured. The umask is reset. + It is recommended for new-style daemons to implement the following: @@ -251,7 +250,7 @@ detect service errors and problems. It is recommended to follow the exit code scheme as defined in the LSB + url="http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html">LSB recommendations for SysV init scripts. @@ -322,29 +321,21 @@ interface. Instead of using the - syslog() call to log directly to the - system syslog service, a new-style daemon may - choose to simply log to STDERR via - fprintf(), which is then forwarded to - syslog by the init system. If log - priorities are necessary, these can be - encoded by prefixing individual log - lines with strings like "<4>" - (for log priority 4 "WARNING" in the - syslog priority scheme), following a - similar style as the Linux kernel's - printk() priority system. In fact, - using this style of logging also - enables the init system to optionally - direct all application logging to the - kernel log buffer (kmsg), as - accessible via - dmesg1. This - kind of logging may be enabled by - setting - StandardError=syslog - in the service unit file. For details, - see + syslog() call to + log directly to the system syslog + service, a new-style daemon may choose + to simply log to standard error via + fprintf(), which + is then forwarded to syslog by the + init system. If log priorities are + necessary, these can be encoded by + prefixing individual log lines with + strings like "<4>" (for log + priority 4 "WARNING" in the syslog + priority scheme), following a similar + style as the Linux kernel's + printk() priority + system. For details, see sd-daemon3 and systemd.exec5. @@ -353,7 +344,7 @@ These recommendations are similar but not identical to the Apple + url="https://developer.apple.com/library/mac/documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/CreatingLaunchdJobs.html">Apple MacOS X Daemon Requirements. @@ -394,7 +385,7 @@ exclusively on boot (and manually by the administrator) via SysV init scripts, as detailed in the LSB + url="http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html">LSB Linux Standard Base Core Specification. This method of activation is supported ubiquitously on Linux @@ -765,7 +756,7 @@ PKG_PROG_PKG_CONFIG AC_ARG_WITH([systemdsystemunitdir], - AS_HELP_STRING([--with-systemdsystemunitdir=DIR], [Directory for systemd service files]),, + [AS_HELP_STRING([--with-systemdsystemunitdir=DIR], [Directory for systemd service files])],, [with_systemdsystemunitdir=auto]) AS_IF([test "x$with_systemdsystemunitdir" = "xyes" -o "x$with_systemdsystemunitdir" = "xauto"], [ def_systemdsystemunitdir=$($PKG_CONFIG --variable=systemdsystemunitdir systemd) @@ -774,11 +765,10 @@ AS_IF([test "x$with_systemdsystemunitdir" = "xyes" -o "x$with_systemdsystemunitd [AS_IF([test "x$with_systemdsystemunitdir" = "xyes"], [AC_MSG_ERROR([systemd support requested but pkg-config unable to query systemd package])]) with_systemdsystemunitdir=no], - [with_systemdsystemunitdir=$def_systemdsystemunitdir])]) + [with_systemdsystemunitdir="$def_systemdsystemunitdir"])]) AS_IF([test "x$with_systemdsystemunitdir" != "xno"], [AC_SUBST([systemdsystemunitdir], [$with_systemdsystemunitdir])]) -AM_CONDITIONAL(HAVE_SYSTEMD, [test "x$with_systemdsystemunitdir" != "xno"]) - +AM_CONDITIONAL([HAVE_SYSTEMD], [test "x$with_systemdsystemunitdir" != "xno"]) This snippet allows automatic installation of the unit files on systemd @@ -942,6 +932,14 @@ fi + + Placing Daemon Data + + It is recommended to follow the genreal + guidelines for placing package files, as discussed in + file-hierarchy7. + + See Also @@ -950,7 +948,8 @@ fi sd_listen_fds3, sd_notify3, daemon3, - systemd.service5 + systemd.service5, + file-hierarchy7