X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=man%2Fsd_notify.xml;fp=man%2Fsd_notify.xml;h=41c3f3fa78f5b6506f1a7e9d757fac454d884479;hp=0000000000000000000000000000000000000000;hb=1532f28b7cf3e6e02e74691450b2b5379be6b805;hpb=37570c53dc8865f07ae8ff5a9915d7ed797b951f diff --git a/man/sd_notify.xml b/man/sd_notify.xml new file mode 100644 index 000000000..41c3f3fa7 --- /dev/null +++ b/man/sd_notify.xml @@ -0,0 +1,376 @@ + + + + + + + + + sd_notify + elogind + + + + Developer + Lennart + Poettering + lennart@poettering.net + + + + + + sd_notify + 3 + + + + sd_notify + sd_notifyf + sd_pid_notify + sd_pid_notifyf + sd_pid_notify_with_fds + Notify service manager about start-up completion and other service status changes + + + + + #include <elogind/sd-daemon.h> + + + int sd_notify + int unset_environment + const char *state + + + + int sd_notifyf + int unset_environment + const char *format + ... + + + + int sd_pid_notify + pid_t pid + int unset_environment + const char *state + + + + int sd_pid_notifyf + pid_t pid + int unset_environment + const char *format + ... + + + + int sd_pid_notify_with_fds + pid_t pid + int unset_environment + const char *state + const int *fds + unsigned n_fds + + + + + + Description + sd_notify() may be called by a service + to notify the service manager about state changes. It can be used + to send arbitrary information, encoded in an + environment-block-like string. Most importantly it can be used for + start-up completion notification. + + If the unset_environment parameter is + non-zero, sd_notify() will unset the + $NOTIFY_SOCKET environment variable before + returning (regardless of whether the function call itself + succeeded or not). Further calls to + sd_notify() will then fail, but the variable + is no longer inherited by child processes. + + The state parameter should contain a + newline-separated list of variable assignments, similar in style + to an environment block. A trailing newline is implied if none is + specified. The string may contain any kind of variable + assignments, but the following shall be considered + well-known: + + + + READY=1 + + Tells the service manager that service startup + is finished. This is only used by elogind if the service + definition file has Type=notify set. Since there is little + value in signaling non-readiness, the only value services + should send is READY=1 (i.e. + READY=0 is not defined). + + + + RELOADING=1 + + Tells the service manager that the service is + reloading its configuration. This is useful to allow the + service manager to track the service's internal state, and + present it to the user. Note that a service that sends this + notification must also send a READY=1 + notification when it completed reloading its + configuration. + + + + STOPPING=1 + + Tells the service manager that the service is + beginning its shutdown. This is useful to allow the service + manager to track the service's internal state, and present it + to the user. + + + + STATUS=... + + Passes a single-line UTF-8 status string back + to the service manager that describes the service state. This + is free-form and can be used for various purposes: general + state feedback, fsck-like programs could pass completion + percentages and failing programs could pass a human readable + error message. Example: STATUS=Completed 66% of file + system check... + + + + ERRNO=... + + If a service fails, the errno-style error + code, formatted as string. Example: ERRNO=2 + for ENOENT. + + + + BUSERROR=... + + If a service fails, the D-Bus error-style + error code. Example: + BUSERROR=org.freedesktop.DBus.Error.TimedOut + + + + MAINPID=... + + The main process ID (PID) of the service, in + case the service manager did not fork off the process itself. + Example: MAINPID=4711 + + + + WATCHDOG=1 + + Tells the service manager to update the + watchdog timestamp. This is the keep-alive ping that services + need to issue in regular intervals if + WatchdogSec= is enabled for it. See + elogind.service5 + for information how to enable this functionality and + sd_watchdog_enabled3 + for the details of how the service can check whether the + watchdog is enabled. + + + + + FDSTORE=1 + + Stores additional file descriptors in the + service manager. File descriptors sent this way will be + maintained per-service by the service manager and be passed + again using the usual file descriptor passing logic on the + next invocation of the service (see + sd_listen_fds3). + This is useful for implementing service restart schemes where + services serialize their state to /run, + push their file descriptors to the system manager, and are + then restarted, retrieving their state again via socket + passing and /run. Note that the service + manager will accept messages for a service only if + FileDescriptorStoreMax= is set to non-zero + for it (defaults to zero). See + elogind.service5 + for details. Multiple arrays of file descriptors may be sent + in separate messages, in which case the arrays are combined. + Note that the service manager removes duplicate file + descriptors before passing them to the service. Use + sd_pid_notify_with_fds() to send messages + with FDSTORE=1, see + below. + + + + + It is recommended to prefix variable names that are not + listed above with X_ to avoid namespace + clashes. + + Note that elogind will accept status data sent from a + service only if the NotifyAccess= option is + correctly set in the service definition file. See + elogind.service5 + for details. + + sd_notifyf() is similar to + sd_notify() but takes a + printf()-like format string plus + arguments. + + sd_pid_notify() and + sd_pid_notifyf() are similar to + sd_notify() and + sd_notifyf() but take a process ID (PID) to + use as originating PID for the message as first argument. This is + useful to send notification messages on behalf of other processes, + provided the appropriate privileges are available. If the PID + argument is specified as 0 the process ID of the calling process + is used, in which case the calls are fully equivalent to + sd_notify() and + sd_notifyf(). + + sd_pid_notify_with_fds() is similar to + sd_pid_notify() but takes an additional array + of file descriptors. These file descriptors are sent along the + notification message to the service manager. This is particularly + useful for sending FDSTORE=1 messages, as + described above. The additional arguments are a pointer to the + file descriptor array plus the number of file descriptors in the + array. If the number of file descriptors is passed as 0, the call + is fully equivalent to sd_pid_notify(), i.e. + no file descriptors are passed. Note that sending file descriptors + to the service manager on messages that do not expect them (i.e. + without FDSTORE=1) they are immediately closed + on reception. + + + + Return Value + + On failure, these calls return a negative errno-style error + code. If $NOTIFY_SOCKET was not set and hence + no status data could be sent, 0 is returned. If the status was + sent, these functions return with a positive return value. In + order to support both, init systems that implement this scheme and + those which do not, it is generally recommended to ignore the + return value of this call. + + + + Notes + + + + Internally, these functions send a single datagram with the + state string as payload to the AF_UNIX socket + referenced in the $NOTIFY_SOCKET environment + variable. If the first character of + $NOTIFY_SOCKET is @, the + string is understood as Linux abstract namespace socket. The + datagram is accompanied by the process credentials of the sending + service, using SCM_CREDENTIALS. + + + + Environment + + + + $NOTIFY_SOCKET + + Set by the service manager for supervised + processes for status and start-up completion notification. + This environment variable specifies the socket + sd_notify() talks to. See above for + details. + + + + + + Examples + + + Start-up Notification + + When a service finished starting up, it might issue the + following call to notify the service manager: + + sd_notify(0, "READY=1"); + + + + Extended Start-up Notification + + A service could send the following after completing + initialization: + + sd_notifyf(0, "READY=1\n" + "STATUS=Processing requests...\n" + "MAINPID=%lu", + (unsigned long) getpid()); + + + + Error Cause Notification + + A service could send the following shortly before exiting, on failure: + + sd_notifyf(0, "STATUS=Failed to start up: %s\n" + "ERRNO=%i", + strerror(errno), + errno); + + + + Store a File Descriptor in the Service Manager + + To store an open file descriptor in the service manager, + in order to continue operation after a service restart without + losing state use FDSTORE=1: + + sd_pid_notify_with_fds(0, 0, "FDSTORE=1", &fd, 1); + + + + + See Also + + elogind1, + sd-daemon3, + daemon7, + elogind.service5, + sd_watchdog_enabled3 + + + +