I found two ways for printing boot messages one using dmesg and another the content of file  /var/log/boot.log:The content of the /var/log/boot.log file are: fsck from util-linux 2.20.1/dev/loop0: clean, 263563/2271232 files, 7843644/18169856 blocks * Starting configure network device security^[[74G[ OK ] * Starting configure network device security^[[74G[ OK ] * Starting configure network device^[[74G[ OK ] * Starting Mount network filesystems^[[74G[ OK ] * Starting Failsafe Boot Delay^[[74G[ OK ] * Stopping Mount network filesystems^[[74G[ OK ] * Starting Bridge socket events into upstart^[[74G[ OK ] * Starting mDNS/DNS-SD daemon^[[74G[ OK ] * Starting Userspace bootsplash^[[74G[ OK ] * Starting Send an event to indicate plymouth is up^[[74G[ OK ] * Starting bluetooth daemon^[[74G[ OK ] * Starting configure network device^[[74G[ OK ] * Stopping Failsafe Boot Delay^[[74G[ OK ] * Starting System V initialisation compatibility^[[74G[ OK ] * Starting set sysctls from /etc/sysctl.conf^[[74G[ OK ] * Starting configure network device security^[[74G[ OK ] * Starting modem connection manager^[[74G[ OK ] * Stopping set sysctls from /etc/sysctl.conf^[[74G[ OK ] * Starting CUPS printing spooler/server^[[74G[ OK ] * Starting network connection manager^[[74G[ OK ] * Stopping cold plug devices^[[74G[ OK ] * Stopping log initial device creation^[[74G[ OK ] * Starting configure network device security^[[74G[ OK ] * Starting save udev log and update rules^[[74G[ OK ] * Stopping save udev log and update rules^[[74G[ OK ] * Stopping Userspace bootsplash^[[74G[ OK ]Skipping profile in /etc/apparmor.d/disable: usr.bin.firefoxSkipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd * Starting AppArmor profiles       ^[[170G^[[164G[ OK ]speech-dispatcher disabled; edit /etc/default/speech-dispatchersaned disabled; edit /etc/default/saned * Stopping System V initialisation compatibility^[[74G[ OK ] * Starting System V runlevel compatibility^[[74G[ OK ]while dmesg gives some thing like this:[    0.008660] Initializing cgroup subsys blkio[    0.008663] Initializing cgroup subsys perf_event[    0.008667] Initializing cgroup subsys hugetlb[    0.008713] CPU: Physical Processor ID: 0[    0.008716] CPU: Processor Core ID: 0[    0.008720] mce: CPU supports 4 MCE banks[    0.008739] CPU0: Thermal monitoring enabled (TM1)[    0.008746] process: using mwait in idle threads[    0.008753] Last level iTLB entries: 4KB 64, 2MB 64, 4MB 64[    0.008753] Last level dTLB entries: 4KB 64, 2MB 0, 4MB 64[    0.008753] tlb_flushall_shift: 6[    0.008895] Freeing SMP alternatives: 24k freed[    0.011699] ACPI: Core revision 20121018[    0.016015] ftrace: allocating 29358 entries in 115 pages[    0.028544] ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1[    0.068468] smpboot: CPU0: Intel(R) Pentium(R) 4 CPU 3.00GHz (fam: 0f, model: 04, stepping: 09)[    0.072000] Performance Events: Netburst events, Netburst P4/Xeon PMU driver.[    0.072000] ... version:                0and so on  So my question how are the two related? When should we use demsg and when boot.log?
Interpreting output of dmesg and /var/log/boot.log
boot;logs;dmesg