Segmentation Fault What are segmentation faults (segfaults), and how can I identify what’s causing them? Debugging Segmentation Faults and Pointer Problems Debugging with GDB GDB Command Reference (gdb) info frame Stack level 0, frame at 0xb75f7390: eip = 0x804877f in base::func() (testing.cpp:16); saved eip 0x804869a called by frame at 0xb75f73b0 source language c++.… Continue reading Segmentation Fault

Breaking yum infinite loop

When executing “yum update openssl*”, it seems yum runs into infinite loop: –> Running transaction check —> Package gmp.x86_64 0:4.3.1-7.el6_2.2 will be updated –> Processing Dependency: for package: cloog-ppl-0.15.7-1.2.el6.x86_64 –> Processing Dependency: for package: ppl-0.10.2-11.el6.x86_64 —> Package python.x86_64 0:2.6.6-29.el6_2.2 will be updated –> Processing Dependency: python(abi) = 2.6 for package: pygtksourceview-2.8.0-1.el6.x86_64 –> Processing… Continue reading Breaking yum infinite loop

Something you need to know about NTP, timezone and system time

NOTE: All the answers are excerpts from related reference web pages. How time zones are handled with NTP? NTP does not regconize time zones, instead it manages all time information based on UTC. In general the handling of time zones is a job of a computer’s operating system. Under Windows, Linux and FreeBSD the system… Continue reading Something you need to know about NTP, timezone and system time

Processes and Threads in Linux

Linux /var/log/messages show the following info and the host hung: automount[4483]: expire_proc: expire thread create for /misc failed Why does a server crash with automount failing to create threads ? The issue is related to the maximum number of processes respectively the kernel parameter kernel.pid_max The following is the explanation of pid_max: /proc/sys/kernel/pid_max (since… Continue reading Processes and Threads in Linux

Analyzing multiple accesslog files

— generate beBigAndTradeDepositByTremList access history frequency for each access log per minute for i in `ls -ltr | grep -i access| awk ‘{print $NF}’` do name=`ls -l | grep -w $i | awk ‘{print $6″”$7}’|sed ‘s/://g’` grep beBigAndTradeDepositByTremList $i | awk ‘{print $3}’ | awk -F: ‘{print $1″:”$2}’ | uniq -c | awk ‘{print $2,$1}’… Continue reading Analyzing multiple accesslog files

Using pipe to concurrently execute programs in bash 1 #!/bin/bash 2 3 your_func() 4 { # use your cmd or func instead of sleep here. don’t end with background(&) 5 date +%s 6 echo “scp HOSTNAME:/home/USER/path/from/file.$1 REMOTE_HOST:/home/USER/path/to/” 7 sleep 2 8 } 9 10 concurrent() 11 { # from $1 to $2, (included $1,$2 itself), con-current $3 cmd 12 start=$1 && end=$2… Continue reading Using pipe to concurrently execute programs in bash