System Recovery

Tizen 4.0 comes with 3 different root filesystems, each designed for a different purpose.

Table: Root filesystems

Label Purpose
rootfs Main root filesystem
ramdisk Regular boot ramdisk
ramdisk-recovery System recovery ramdisk

This topic describes operation and customization options of the system recovery ramdisk.

The following steps describe the boot process:

  1. The boot process starts with a bootloader (u-boot or s-boot) loading appropriate kernel and ramdisk images dedicated for the system recovery process (methods for controlling bootloader actions are beyond the scope of this document). With both images loaded into RAM, the kernel initialization begins. When the initialization is complete, the kernel passes control to the init process, such as /sbin/init (PID#1).

  2. In the case of the recovery ramdisk, /sbin/init is a symlink to /usr/libexec/initrd-recovery/init (a shell script that comes from the initrd-recovery package). The script mounts several kernel filesystems and the inform partition (if it exists), and parses the kernel command line options (/proc/cmdline) to find the bootmode parameter. If the parameter is present, one of the /sbin/*-init scripts is started. If the boot mode is set to recovery, /usr/libexec/system-recovery/recovery-init is started.

  3. The recovery-init script mounts the real root filesystem under the /system directory, and other filesystems (such as /opt and /opt/usr) below the /system directory. The script starts a shell on the serial console and launches the system-recovery program.

  4. The system-recovery program searches the removable storage for tizen-recovery.img which has the compressed partition image and config file. The system-recovery program decompress tizen-recovery.img, and dumps the partition image to the appropriate block as mentioned in the config file.

Adding New Files to the ramdisk-recovery Partition

The ramdisk-recovery partition is created along with the rootfs partition (methods for creating images are beyond the scope of this document):

  • Files to be added to the ramdisk-recovery partition must be available in Tizen RPM packages.
  • Files are added to the partition by the mkinitrd-recovery.sh script, which is started automatically as a part of the %posttrans RPM script of the initrd-recovery package.

To install a selected file in the recovery image, its RPM needs to be installed before initrd-recovery is run. The easiest way to make sure this happens is to list the package as a dependency in the initrd-recovery.spec file.

The mkinitrd-recovery.sh script copies or moves files from the rootfs partition to the initrd-recovery partition according to directions provided in configuration files stored in the /usr/share/initrd-recovery/initrd.list.d directory. These files must be packaged in the RPM packages together with the files to be put on the initrd-recovery partition. The configuration files are interpreted as shell scripts and can be used to set the following variables:

  • DIRECTORIES: Create directories.
  • DIR_SYMLINKS: Create symbolic links to directories.
  • LIBONLYS: Copy only the libraries required by the listed executable files.
  • MVWITHLIBS: Move the listed executable files and copy the required libraries.
  • SYMLINKS: Create symbolic links.
  • VERBATIMS: Copy the listed files. List non-executable files here.
  • WITHLIBS: Copy the listed executable files and the required libraries.

The SYMLINKS and DIR_SYMLINKS variables contain pairs of filenames separated with colons.

The following section contains examples of the above variables:

DIRECTORIES="
/var/tmp
/usr/lib/odbc
"

# LinkFileName:Target
DIR_SYMLINKS="
/lib:usr/lib
/opt:system/opt
"

LIBONLYS="
/bin/bash
/bin/kill
"

MVWITHLIBS="
/usr/libexec/initrd-recovery/minireboot
/usr/libexec/system-recovery/system-recovery.gui
"

WITHLIBS="
/usr/bin/sync
/usr/bin/touch
"

VERBATIMS="
/usr/share/system-recovery/res/images/font.png
/usr/share/system-recovery/res/images/menu-title.png
/usr/share/system-recovery/system-recovery.cfg
"

# LinkFileName:Target
SYMLINKS="
/sbin/recovery-init:/usr/libexec/system-recovery/recovery-init
/usr/lib/bufmgr/libtbm_default.so:libtbm_sprd.so
"

The following real-world example comes from the initrd-recovery package. Following this configuration, mkinitrd-recovery.sh copies some basic tools to the initrd-recovery partition, moves init and minireboot, and creates some symlinks:

MVWITHLIBS="
/usr/libexec/initrd-recovery/init
/usr/libexec/initrd-recovery/minireboot
"

WITHLIBS="
/usr/bin/bash
/usr/bin/cat
/usr/bin/mkdir
/usr/bin/mount
/usr/bin/sleep
/usr/bin/sync
/usr/bin/umount
/usr/sbin/blkid
"

# LinkFileName:Target
SYMLINKS="
/bin/sh:bash
/sbin/init:/usr/libexec/initrd-recovery/init
/sbin/minireboot:/usr/libexec/initrd-recovery/minireboot
/sbin/reboot:/usr/libexec/initrd-recovery/minireboot
"