From dbbba9dd08c6225b8c443eb9e03eda3a40334781 Mon Sep 17 00:00:00 2001 From: Sebastiano Tronto Date: Fri, 8 Jul 2022 06:18:01 +0200 Subject: New blog post --- src/blog/2022-07-07-shutdown/shutdown.md | 125 +++++++++++++++++++++++++++++++ src/blog/blog.md | 1 + src/blog/feed.xml | 7 ++ 3 files changed, 133 insertions(+) create mode 100644 src/blog/2022-07-07-shutdown/shutdown.md (limited to 'src') diff --git a/src/blog/2022-07-07-shutdown/shutdown.md b/src/blog/2022-07-07-shutdown/shutdown.md new file mode 100644 index 0000000..b6ff7be --- /dev/null +++ b/src/blog/2022-07-07-shutdown/shutdown.md @@ -0,0 +1,125 @@ +# The man page reading club: shutdown(8) + +I would like to write about more interesting things, but I do not have +time or energy to do so. I need to shut down for a little while. + +## Sleeping in a sleepless time + +*Reading. Learning. Fun. Tired.* + +``` +$ date +Thu Jul 7 22:57:50 CEST 2022 +``` + +*Not too late. You should do something.* + +``` +$ man man +NAME + man - display manual pages +``` + +*No, you have already done that one. What should you do?* + +``` +$ date +Thu Jul 7 22:59:48 CEST 2022 +``` + +*This is not going anywhere. Is it time to go to sleep? Who knows, +during the covid lockdown - ahem, nuclear winter - every hour looks the same. +Maybe it is time to go to sleep. To shutdown.* + +## shutdown(8) + +*Follow along at [man.openbsd.org](https://man.openbsd.org/OpenBSD-7.1/shutdown)* + +``` +SYNOPSIS + shutdown [-] [-dfhknpr] time [warning-message ...] + +DESCRIPTION + shutdown provides an automated shutdown procedure for superusers to + nicely notify users when the system is shutting down, saving them from + system administrators, hackers, and gurus, who would otherwise not bother + with such niceties. When the shutdown command is issued without options, + the system is placed in single user mode at the indicated time after + shutting down all system services. +``` + +As it sometimes happens, the first few lines of the manual page hint to some +arcane background that you cannot quite grasp. However, the bottom line is +clear: `shutdwon` shuts the system down. + +``` +The options are as follows: + -d When used with -h, -p, or -r causes system to perform a dump. + This option is useful for debugging system dump procedures [...]. +``` + +Good to keep in mind. But this time we are not in for an in-depth analysis of +a classic UNIX command. We just want to shut down. Let's skip a few of the +other options. + +``` + -p The system is powered down at the specified time. The -p flag is + passed on to halt(8), causing machines which support automatic + power down to do so after halting. + + -r shutdown execs reboot(8) at the specified time. +``` + +Yes, these sound like things I would like to do. How do I tell it to +shut down now? + +``` + time time is the time at which shutdown will bring the system down and + may be the word now (indicating an immediate shutdown) or specify + a future time in one of two formats: +number or yymmddhhmm, + where the year, month, and day may be defaulted to the current + system values. The first form brings the system down in number + minutes and the second at the absolute time specified. +``` + +Great! + +``` + warning-message + Any other arguments comprise the warning message that is + broadcast to users currently logged into the system. + - If `-' is supplied as an option, the warning message is read from + the standard input. +``` + +Who do we have to warn about the shutdown? We are the only user anyway, right? + +``` +# echo 'the hours rise up putting off stars and it is +> dawn' | shutdown -p now - +``` + +## Conclusions + +At the moment of writing this blog post, I am tired. I had a busy week. +I wanted to write an interesting blog post about something like +sh(1), but I could not find the time. However, shutting down my pc earlier +today inspired me to write this short blog entry. + +`shutdown` is an interesting command. It seems like it should be +straightforward: "computer, please shut down". But the syntax for this +simple instruction is quite complicated, and it offers us many more option +than we would ever want to use, at least in the 21st century. Moreover, as +indicated by the `#` instead of the `$` in the last command, one needs +superuser privileges to shut down a classic UNIX system. + +This is because, in the time of mainframes, *shutting down* was not such a +simple operation: multiple users might have been connected to the main +computer, and shutting the whole system down without at least telling them +was rude. At least this is my guess, I was not there at the time. + +It would certainly be interesting to dig into the history of computer systems, +mainframes and how administrators used to shut them down when multiple users +where logged in. But I am not going to do it now. + +Good night. diff --git a/src/blog/blog.md b/src/blog/blog.md index 5b777ad..7b8095b 100644 --- a/src/blog/blog.md +++ b/src/blog/blog.md @@ -2,6 +2,7 @@ [RSS Feed](feed.xml) +* 2022-07-07 [The man page reading club: shutdown(8)](2022-07-07-shutdown) * 2022-06-12 [The UNIX shell as an IDE: look stuff up with sed](2022-06-12-shell-ide-sed) * 2022-06-08 [The man page reading club: more(1)](2022-06-08-more) * 2022-06-04 [The gemini protocol](2022-06-04-gemini) diff --git a/src/blog/feed.xml b/src/blog/feed.xml index 567c6b2..a91f184 100644 --- a/src/blog/feed.xml +++ b/src/blog/feed.xml @@ -8,6 +8,13 @@ Thoughts about software, computers and whatever I feel like sharing + +The man page reading club: shutdown(8) +https://sebastiano.tronto.net/blog/2022-07-07-shutdown +The man page reading club: shutdown(8) +2022-07-07 + + The UNIX shell as an IDE: look stuff up with sed https://sebastiano.tronto.net/blog/2022-06-12-shell-ide-sed -- cgit v1.3