Archive for 'Linux Utilities'

Sudo insults — what a fun feature!

I think humor plays a big role in life, especially the life of a SysAdmin. This weekend I was cleaning up some sudoers files and came across a reference to the “insult” option in the documentation. Here is what the manual says: “insults If set, sudo will insult users when they enter an incorrect password. […]

Summarizing system call activity on Linux systems

Linux has a guadzillion debugging utilities available. One of my favorite tools for debugging problems is strace, which allows you to observe the system calls a process is making in realtime. Strace also has a “-c” option to summarize system call activity: $ strace -c -p 28009 Process 28009 attached Process 28009 detached % time […]

Breaking the telnet addiction with netcat

After many years of use it’s become almost second nature to type ‘telnet <HOST> <PORT>’ when I need to see if a system has TCP port <PORT> open. Newer systems no longer install telnet by default: $ telnet google.com 80 -bash: telnet: command not found I can’t think of a valid reason to keep telnet […]

Using the automated bug-reporting tool (abrt) to generate core dumps when a Linux process fails

Software fails, and it often occurs at the wrong time. When failures occur I want to understand why, and will usually start putting together the events that lead up to the issue. Some application issues can be root caused by reviewing logs, but catastrophic crashes will often require the admin to sit down with gdb […]

Using exec-shield to protect your Linux servers from stack, heap and integer overflows

I’ve been a long time follower of the OpenBSD project, and their amazing work on detecting and protecting the kernel and applications from stack and heap overflows. Several of the concepts that were developed by the OpenBSD team were made available in Linux, and came by way of the exec-shield project. Of the many useful […]

Fcron, a feature rich cron and anacron replacement

I’ve been looking at some opensource scheduling packages, and while doing my research I came across the fcron package. Fcron is a replacement for vixie cron and anacron, and provides a number of super useful features: – Run jobs based on the system load average. – Serialize jobs. – Set the nice value of the […]

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