crontabs?

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Jun 18, 2024 at 19:10	comment	added	QF0		Ah - ok - it all makes sense now :) If someone wants to write up an `fs.protected_regular` answer I'll accept it.
Jun 18, 2024 at 19:01	comment	added	QF0		@user4556274: on the dupe - yes, I saw that, thanks, and the `fs.protected_regular` sysctl does let me edit the file, as more-or-less suggested in the comments above. Your suggestion of editing as the user and group also works (why?). However, I'm still trying to get my head around why `fs.protected_regular` is relevant, since root owns the directory and the file, and the kernel.org docs explicitly state unless they are owned by the owner of the directory.
Jun 18, 2024 at 17:12	comment	added	user4556274		You should be able to edit the file directly ("magic") by running your editor as the user and group owning the file, e.g. `sudo -u sysadmin -g crontab vi /var/spool/cron/crontabs/sysadmin` or `echo "# foo" \| sudo -u sysadmin -g crontab tee -a /var/spool/cron/crontabs/sysadmin`
Jun 18, 2024 at 16:52	comment	added	user4556274		Possible duplicate: unix.stackexchange.com/questions/691441/…
Jun 18, 2024 at 15:09	comment	added	QF0		@JosephSible-ReinstateMonica: `cat /proc/sys/fs/protected_regular` gives 2, and `ls -ld` gives `drwx-wx--T 2 root crontab`.
Jun 18, 2024 at 14:53	comment	added	Joseph Sible-Reinstate Monica		What does `ls -ld /var/spool/cron/crontabs/` say? What is the `fs.protected_regular` sysctl set to?
Jun 18, 2024 at 14:31	history	edited	QF0	CC BY-SA 4.0	added 427 characters in body
Jun 18, 2024 at 14:24	comment	added	QF0		@JosephSible-ReinstateMonica: `# echo "foo" >> sysadmin` reports `bash: sysadmin: Permission denied`. Root can't write the file; it can only delete the file. This smells like a kernel config of some sort, like a write to a file in `/tmp`, but I can't find any docs on it.
Jun 18, 2024 at 14:21	comment	added	QF0		@steeldriver: I know that I can edit it with `crontab -e` - what I'm trying to find out is what magic `crontab` is using to allow the file to be written to, when a root user can do nothing apart from deleting the file? I'm assuming that there's a kernel config of some sort that's stopping me doing this, hence the `sysctl` tag.
Jun 18, 2024 at 3:50	comment	added	Joseph Sible-Reinstate Monica		Can you edit it with vi or nano, or do things like `echo '# hello' >> /var/spool/cron/crontabs/sysadmin`?
Jun 18, 2024 at 1:18	comment	added	waltinator		You should include `(server-start)` in your `~/.emacs`, and `export EDITOR="$(type -p emacsclient)";`export VISUAL="$(type -p emacsclient)";alias emacs="$(type -p emacsclient)"` to your shell startup file. Start 1 `/usr/bin/emacs` at login. Once `EDITOR` and `VISUAL` are set, you can use `sudoedit` to edit a file (`sudoedit`, running as `root`, copies the target file to a temporary location (changing ownership to `$USER`), then, running as `$USER`, invokes `$EDITOR` or `$VISUAL` on the temporary copy. If the copy is changed, `sudoedit`, running as `root` copies it back.
Jun 17, 2024 at 23:17	history	edited	Marcus Müller	CC BY-SA 4.0	edited title
Jun 17, 2024 at 19:43	comment	added	steeldriver		You can (and should) use `crontab -e` regardless of which editor you want to use - just specify emacs via the EDITOR or VISUAL environment variable. See for example crontab -e doesnt shows option to select editor - what to do?
Jun 17, 2024 at 16:29	history	edited	QF0	CC BY-SA 4.0	added 248 characters in body
Jun 17, 2024 at 16:09	comment	added	terdon♦		Please edit your question and show us i) how you try to edit it and ii) how it fails. Is there an error? What error? Is there no error but your changes disappear? What happens?
Jun 17, 2024 at 15:53	comment	added	QF0		@Kusalananda: I can't edit it with emacs - I assume that `crontab -e` would work.
Jun 17, 2024 at 15:34	comment	added	Kusalananda♦		You mean you can't edit it with `crontab -u sysadmin -e` as root?
Jun 17, 2024 at 15:25	history	asked	QF0	CC BY-SA 4.0

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