Sysupgrade – Technical Reference

In contrast to opkg, mtd and others, sysupgrade is merely a shell script: /sbin/sysupgrade intended to facilitate easy updates.

This page lists all sysupgrade command-line options. For the overall upgrade procedure and typical usage, please read OpenWrt OS upgrade procedure (sysupgrade or LuCI) instead.

sysupgrade supports the following options (r34975):

Usage: /sbin/sysupgrade [<upgrade-option>...] <image file or URL>
       /sbin/sysupgrade [-q] [-i] <backup-command> <file>

upgrade-option:
        -d <delay>   add a delay before rebooting
        -f <config>  restore configuration from .tar.gz (file or url)
        -i           interactive mode
        -c           attempt to preserve all changed files in /etc/
        -n           do not save configuration over reflash
        -p           do not attempt to restore the partition table after flash.
        -T | --test
                     Verify image and config .tar.gz but do not actually flash.
        -F | --force
                     Flash image even if image checks fail, this is dangerous!
        -q           less verbose
        -v           more verbose
        -h | --help  display this help

backup-command:
        -b | --create-backup <file>
                     create .tar.gz of files specified in sysupgrade.conf
                     then exit. Does not flash an image. If file is '-',
                     i.e. stdout, verbosity is set to 0 (i.e. quiet).
        -r | --restore-backup <file>
                     restore a .tar.gz created with sysupgrade -b
                     then exit. Does not flash an image. If file is '-',
                     the archive is read from stdin.
        -l | --list-backup
                     list the files that would be backed up when calling
                     sysupgrade -b. Does not create a backup file.

WARNING: Preserving files across sysupgrades can be fatal (see 'NOTE: ...') on systems with weak cpu and exceptionally large rootfs_data partitions.

Files to be preserved depend on the following:

• /etc/sysupgrade.conf - customizable backup configuration.
• /lib/upgrade/keep.d/* - system configurations provided by specific packages preserved by default.
• opkg list-changed-conffiles - list of files derived by package manager.

SAVE_OVERLAY saves the complete /overlay directory. There's no rule what needs to be saved... sometimes I install additional packages but then include them in the later firmware builds, so I don't have to preserve those. Sometimes files are modified and the new firmware already contains the modifications so those are also not needed. But config files are needed or router will boot with default settings. But those are preserved by default (unless using -n).

-- Does this mean, I make an archive.tar.gz of /etc and /root for example and sysupgrade -f archive.tar.gz will flash the router and afterwards restores the configs from this archive?

That's what is says: 'restore configuration from .tar.gz (file or url)'. Anything archived in the tgz will be written to /overlay after the flash. This way you can hand-pick the files that will be the system after new firmware boot.