Test it on a lab or non-production server first. The upgrade from 1.5 to 1.6 is one-way: it changes the database schema, and there is no down-migration.

Changed since RC-18

• Service restarts no longer flood servicemaster.log with PHP warnings (#1994, #1996). A service’s supervisor closes its database connection before it starts each worker. Its next log line could read a setting on that closed connection, which wrote “Trying to access array offset on false” at FOGBase.php lines 3747 and 3752. The supervisor now reopens the connection before it logs. A failed settings read no longer warns, and it no longer empties the settings cache.
• SSH: no more “Undefined array key “_link”” warning, and no fatal after a failed connect (#1997, #1999). FOGSSH::disconnect() unset its connection, so the next use of the shared SSH object warned. A disconnect with no live session also threw a TypeError on PHP 8.
• User export imports back (#1987, #1993). A user row with no password gets a random password and a warning to set one. A password hash is stored as-is, and a typed password is hashed. A new permission, user.export, adds “Include password hashes” to the user export page. It is denied by default, and each hash export writes an audit row.
• The installer warns about no_root_squash only on the <share>/dev export (#1988, #1990). An unrelated export, such as an ISO share, no longer raises the warning. Thanks to sgennadi, who reported it and proposed the fix.

FOS (kernel and init), from the Latest FOS release

An RC install or update downloads the Latest FOS release. Latest is still EXP_20261027-181357, unchanged since RC-18:

• Kernel 6.18.59, the current 6.18 LTS release.
• FOS verifies TLS, which is the client half of #1978.
• The Performance Test task.
• x64 and x86 boot an initramfs, not an ext2 initrd (FOGProject/fos#75). The file names stay init.xz and init_32.xz, and the boot menu does not change. /tmp is now a real RAM disk with a size limit: FOG_KERNEL_RAMDISK_SIZE sets the size, kept between 64 MB and half of the client’s memory.
  • Warning: a customized init can no longer be loop-mounted. Add your files as an overlay cpio appended to init.xz instead: https://docs.fogproject.org/en/latest/kb/how-tos/customize-the-fos-init/ . A post-init script needs no rebuild at all: https://docs.fogproject.org/en/latest/kb/how-tos/post-init-scripts/
  • If a client fails to boot with this init, go to FOG Configuration > Initrd Update and install the init from EXP_20261027-155909, the last ext2 init. Then report it on FOGProject/fos#75.

API documentation: https://docs.fogproject.org/en/latest/1.6/kb/integrations/api

Before you upgrade

• Back up your database and /opt/fog/.fogsettings.
• Read the release notes: https://github.com/FOGProject/fogproject/blob/rc-1.6.0/docs/release/1.6.0-release-notes.md
• 1.6 removes Display Manager, Directory Cleaner, User Cleanup, Client Updater, Green FOG and the persistentgroups plugin. Their data is dropped. The site and accesscontrol plugins move into core.
• PHP 7.4 or later is required. Plugins built for 1.5 do not load.

Install or update (as root)

• A 1.6 beta or RC server: run bin/updatefog.sh --channel rc from your FOG checkout.
• A 1.5 server installed from git: update to the current 1.5 stable, then run bin/updatefog.sh --channel rc from the checkout.
• A new server, or a 1.5 server installed from a tarball:
  curl -fsSL https://raw.githubusercontent.com/FOGProject/fogproject/working-1.6/bin/bootstrap.sh | bash -s -- --channel rc

Report problems

Open an issue at https://github.com/FOGProject/fogproject/issues. Include your FOG version, your OS, and the installer log from bin/error_logs/. Report a security problem through “Report a vulnerability” on the same repository, not in a public issue.