A legacy SysVinit appliance boots into runlevel 5 and must instead come up in runlevel 3 at every boot. Which line in /etc/inittab do you change?
LPIC-1 Exam 101-500, objective 101. System architecture medium
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The options
Correct id:5:initdefault:
Correct. The initdefault entry's runlevel field is the runlevel init enters when no runlevel is given on the kernel command line; changing the 5 to a 3 makes it permanent.
Not correct l5:5:wait:/etc/rc.d/rc 5
Wrong. That entry defines what running runlevel 5 consists of, namely executing the rc script with argument 5. Editing it changes the contents of runlevel 5 rather than which runlevel is entered.
Not correct si::sysinit:/etc/rc.d/rc.sysinit
Wrong. The sysinit entry runs once during system initialisation, before any runlevel is entered, and its runlevel field is deliberately empty.
Not correct ca::ctrlaltdel:/sbin/shutdown -t3 -r now
Wrong. This entry defines what happens when init is told the Ctrl-Alt-Del key combination was pressed.
Why
Each inittab line has four colon-separated fields: an identifier, the runlevels it applies to, an action, and the process to run. The action keyword is what distinguishes the entries, and initdefault is special in that its process field is ignored and only its runlevel field is read. Note the two limits: initdefault must not name runlevel 0 or 6, or the machine would halt or reboot on every boot, and a runlevel given on the kernel command line overrides it for that boot. On a systemd machine the equivalent decision is the default.target symlink.
Where this comes from
- Cited
- manual page inittab(5)
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