Extract the Linux serial number without sudo

dmidecode reads this information from physical memory, using /dev/mem, which requires root.

The same information is also provided by the Linux kernel via sysfs in a virtual directory, /sys/devices/virtual/dmi/id.

Unfortunately, someone decided that all information in that virtual directory is open to anyone for reading, just not the serial numbers:

$ ls -l /sys/devices/virtual/dmi/id

-r--r--r-- 1 root root 4096 Nov 25 17:12 bios_date
-r--r--r-- 1 root root 4096 Nov 14 14:59 bios_vendor
-r--r--r-- 1 root root 4096 Nov 25 17:12 bios_version
-r--r--r-- 1 root root 4096 Nov 25 17:12 board_asset_tag
-r--r--r-- 1 root root 4096 Nov 25 17:12 board_name
-r-------- 1 root root 4096 Nov 25 17:12 board_serial
-r--r--r-- 1 root root 4096 Nov 14 14:59 board_vendor
-r--r--r-- 1 root root 4096 Nov 25 17:12 board_version
-r--r--r-- 1 root root 4096 Nov 25 17:12 chassis_asset_tag
-r-------- 1 root root 4096 Nov 25 17:12 chassis_serial
-r--r--r-- 1 root root 4096 Nov 25 17:12 chassis_type
-r--r--r-- 1 root root 4096 Nov 25 17:12 chassis_vendor
-r--r--r-- 1 root root 4096 Nov 25 17:12 chassis_version
-r--r--r-- 1 root root 4096 Nov 25 17:12 modalias
drwxr-xr-x 2 root root    0 Nov 25 17:12 power
-r--r--r-- 1 root root 4096 Nov 14 14:59 product_name
-r-------- 1 root root 4096 Nov 25 17:12 product_serial
-r-------- 1 root root 4096 Nov 14 14:59 product_uuid
-r--r--r-- 1 root root 4096 Nov 14 14:59 product_version
lrwxrwxrwx 1 root root    0 Nov 14 14:59 subsystem -> ../../../../class/dmi
-r--r--r-- 1 root root 4096 Nov 14 14:59 sys_vendor
-rw-r--r-- 1 root root 4096 Nov 14 14:59 uevent

If you can install package hal (not installed by default on recent Ubuntu versions), this command will work for you as non-root:

 lshal | grep system.hardware.serial

 system.hardware.serial = '<serial_number>'  (string)

This works because package hal installs the hald daemon, which runs as root and collects this data, making it possible for lshal to read it as non-root.