How to add vi to a ramdisk for debug purposes

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Environment

SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server 12 Service Pack 1
SUSE Linux Enterprise Server 12 Service Pack 2

Situation

A system is not booting up properly and exiting to an emergency shell. As the default emergency shell does not contain any editor, changing files in the system can be challenging.

Resolution

The following steps will add vi to the initrd:

Add install_items+="/bin/vi" to a custom dracut.conf file (e.g. /etc/dracut.conf.d/10-debugme.conf, assuming vi(m) has been installed before)
Rebuild the ramdisk by invoking the mkinird wrapper script, or by calling dracut --rebuild directly.

Cause

To keep the ramdisk as small as possible, vi / vim was not included in the ramdisk by default.

Additional Information

For checking, if it has been added properly, please check:

hoth:~ # lsinitrd | grep "bin/vi"
lrwxrwxrwx   1 root     root            3 Mar 24 11:06 bin/vi -> vim
-rwxr-xr-x   1 root     root      2417808 Mar 24 11:06 bin/vim
hoth:~ #

For testing, if the editor would work for you, feel free to boot directly in a emergency shell by adding rd.break as a kernel cmdline option.
This will drop off to a shell after processing the ramdisk (note: to edit files persistently in your root filesystem mounted in /sysroot, it is necessary to

remount it in read-write mode (mount -o remount,rw /sysroot).

Disclaimer

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