f1e24a259c
Why --- The advantage of this is that starting sysinit.target from the emergency shell will no longer kill the emergency shell and lock you out of the system. Our docs already claimed that emergency.target was useful for "starting individual units in order to continue the boot process in steps". This resolves #6509 for my purposes. Remaining limitation -------------------- Starting getty.target will still kill the shell, and if you don't have a root password you will then be locked out at that point. This is relevant to distributions which patch the sulogin system to permit logins when the root password is locked. Both Debian and RedHat used to follow this behaviour! Debian have been discussing what they could replace it with at https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=806852 So this doesn't quite achieve perfection, but I think it's a worthwhile change. It should be easier to understand the logic now it doesn't have such a big hole in it. Repairing the sysinit stage of the boot is the main reason we have emergency.target. And as discussed in the issue, sysinit.target gets pulled in implicitly as soon as any DefaultDependencies service is activated. How --- sysinit.target only needs to conflict with emergency.target. It didn't need to conflict with emergency.service as well. In theory the conflicts are pointless, we could just change the dependency of sysinit.target on local-fs.target from Wants to Requires. However, doing so would mean that when local-fs fails, the screen is flooded with yellow [DEPEND] failures. That would hinder the poor unfortunate admin, so let's not do that. There is no additional ordering requirement against emergency. If the failure happens, the job for sysinit will be cancelled instantly. We don't need to worry about when sysinit.target and its dependents would be stopped, because sysinit waits for local-fs before it starts. emergency.target is still necessarily stopped once we reach sysinit (you can't express a one-way conflict in pure unit directives). This is largely cosmetic... though perhaps it symbolizes that you're no longer in Emergency Mode if System Initialization is successful ;-). As a secondary advantage, the getty's which conflict on rescue.service now need to conflict on emergency.service as well. This makes the system more uniform and simpler to understand. The only other effect this should have is that `systemctl start emergency.target` is now practically the same as `systemctl start rescue.target`. The only units this command will stop are the conflicting getty units. Neither of those commands should ever be used. E.g. they will not stop the gdm.service unit on Fedora 26.
59 lines
2 KiB
Plaintext
59 lines
2 KiB
Plaintext
# This file is part of systemd.
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#
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# systemd is free software; you can redistribute it and/or modify it
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# under the terms of the GNU Lesser General Public License as published by
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# the Free Software Foundation; either version 2.1 of the License, or
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# (at your option) any later version.
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[Unit]
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Description=Getty on %I
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Documentation=man:agetty(8) man:systemd-getty-generator(8)
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Documentation=http://0pointer.de/blog/projects/serial-console.html
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After=systemd-user-sessions.service plymouth-quit-wait.service getty-pre.target
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m4_ifdef(`HAVE_SYSV_COMPAT',
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After=rc-local.service
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)m4_dnl
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# If additional gettys are spawned during boot then we should make
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# sure that this is synchronized before getty.target, even though
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# getty.target didn't actually pull it in.
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Before=getty.target
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IgnoreOnIsolate=yes
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# IgnoreOnIsolate causes issues with sulogin, if someone isolates
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# rescue.target or starts rescue.service from multi-user.target or
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# graphical.target.
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Conflicts=rescue.service emergency.service
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Before=rescue.service emergency.service
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# On systems without virtual consoles, don't start any getty. Note
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# that serial gettys are covered by serial-getty@.service, not this
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# unit.
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ConditionPathExists=/dev/tty0
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[Service]
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# the VT is cleared by TTYVTDisallocate
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# The '-o' option value tells agetty to replace 'login' arguments with an
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# option to preserve environment (-p), followed by '--' for safety, and then
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# the entered username.
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ExecStart=-/sbin/agetty -o '-p -- \\u' --noclear %I $TERM
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Type=idle
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Restart=always
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RestartSec=0
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UtmpIdentifier=%I
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TTYPath=/dev/%I
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TTYReset=yes
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TTYVHangup=yes
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TTYVTDisallocate=yes
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KillMode=process
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IgnoreSIGPIPE=no
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SendSIGHUP=yes
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# Unset locale for the console getty since the console has problems
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# displaying some internationalized messages.
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UnsetEnvironment=LANG LANGUAGE LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT LC_IDENTIFICATION
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[Install]
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WantedBy=getty.target
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DefaultInstance=tty1
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