Re: [systemd-devel] emergency, rescue and single-user

2014-12-09 Thread Mantas Mikulėnas
On Tue, Dec 9, 2014 at 2:43 PM, Jan Synáček jsyna...@redhat.com wrote:

 Hello,

 what is the difference between emergency, rescue and single-user?
 On F21, systemd-216-12.fc21.x86_64, they all boot into something that
 presents itself as Welcome to emergency mode! and they all require a
 root password. In case of booting into emergency.target, I can see
 Starting Emergency Shell in the console output. In single-user and
 rescue.target, I can see Starting Rescue Shell, but they all look the
 same. systemd.special(7) doesn't help much.


rescue.target pulls in sysinit.target (mounts, swaps, udev, sysctl...),
while emergency.target starts a sulogin shell and nothing more. See the
graph in bootup(7).

The sysv single-user mode maps directly to rescue.target.

-- 
Mantas Mikulėnas graw...@gmail.com
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Re: [systemd-devel] emergency, rescue and single-user

2014-12-09 Thread Lennart Poettering
On Tue, 09.12.14 13:43, Jan Synáček (jsyna...@redhat.com) wrote:

 Hello,
 
 what is the difference between emergency, rescue and single-user?
 On F21, systemd-216-12.fc21.x86_64, they all boot into something that
 presents itself as Welcome to emergency mode! and they all require a
 root password. In case of booting into emergency.target, I can see
 Starting Emergency Shell in the console output. In single-user and
 rescue.target, I can see Starting Rescue Shell, but they all look the
 same. systemd.special(7) doesn't help much.

rescue is simply how we call the old sysv single user mode. This
means all early-boot services are started, but no later boot
service. File systems are hence checked, udev is started, and so
on. You get your shell right after sysinit.target but before
basic.target basically.

emergency maps to the emergency mode that sysvinit already knew:
it just starts a shell, and does nothing else. No early-boot services
are run. No udev, no file system checks, no nothing.

Lennart

-- 
Lennart Poettering, Red Hat
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Re: [systemd-devel] emergency, rescue and single-user

2014-12-09 Thread Jan Synacek
Lennart Poettering lenn...@poettering.net writes:
 On Tue, 09.12.14 13:43, Jan Synáček (jsyna...@redhat.com) wrote:

 Hello,
 
 what is the difference between emergency, rescue and single-user?
 On F21, systemd-216-12.fc21.x86_64, they all boot into something that
 presents itself as Welcome to emergency mode! and they all require a
 root password. In case of booting into emergency.target, I can see
 Starting Emergency Shell in the console output. In single-user and
 rescue.target, I can see Starting Rescue Shell, but they all look the
 same. systemd.special(7) doesn't help much.

 rescue is simply how we call the old sysv single user mode. This
 means all early-boot services are started, but no later boot
 service. File systems are hence checked, udev is started, and so
 on. You get your shell right after sysinit.target but before
 basic.target basically.

 emergency maps to the emergency mode that sysvinit already knew:
 it just starts a shell, and does nothing else. No early-boot services
 are run. No udev, no file system checks, no nothing.

 Lennart

Thanks for the explanation!

-- 
Jan Synacek
Software Engineer, Red Hat


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Re: [systemd-devel] emergency, rescue and single-user

2014-12-09 Thread Jan Synacek
Mantas Mikulėnas graw...@gmail.com writes:
 On Tue, Dec 9, 2014 at 2:43 PM, Jan Synáček jsyna...@redhat.com wrote:

 Hello,

 what is the difference between emergency, rescue and single-user?
 On F21, systemd-216-12.fc21.x86_64, they all boot into something that
 presents itself as Welcome to emergency mode! and they all require a
 root password. In case of booting into emergency.target, I can see
 Starting Emergency Shell in the console output. In single-user and
 rescue.target, I can see Starting Rescue Shell, but they all look the
 same. systemd.special(7) doesn't help much.


 rescue.target pulls in sysinit.target (mounts, swaps, udev, sysctl...),
 while emergency.target starts a sulogin shell and nothing more. See the
 graph in bootup(7).

Ok, good to know about bootup(7), thanks!

-- 
Jan Synacek
Software Engineer, Red Hat


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