Profile

Changing the IP address on a Linux system involves both changing the IP address using the ifconfig command and modifying the files that will make your change permanent. The process is very similar to the process you would follow on a Solaris system, except that a different set of files must be modified. The proper steps to take also depend on the particular Linux distribution you are using. Debian systems, for example, use different files to store network configuration than do RedHat systems.

…

The sar command, native to Solaris and often installed on Linux systems via the sysstat package, is extremely useful in analyzing current and recent system performance. On the other hand, if you would like to view performance on your servers over a long time span (more than a month), you need to take some extra steps to preserve your data.

…

If one message stood out among the others at this week's Green Computing Summit in Washington, DC, it was that going green is no longer just good for the bottom line; it's absolutely necessary. And it's not just the tree huggers who are saying so. Prominent business executives and top ranking federal officials are leading a green revolution that promises to radically change computer technology and the way it is managed.

…

When someone first mentioned to me that reports created by running raw access logs through software such as Analog did not meet the needs of high level management, I was caught off guard. "What could possibly be lacking?", I wondered.

…

From the looks of it, ZFS administration is significantly simpler than administration of other complex file systems such as Solaris Disk Suite and Veritas Volume Manager. You can get a lot more done with fewer commands and the chance of making an error that is difficult to back out of is practically non-existent. On the other hand, it's still new to most Unix sysadmins and even those of us who have been working with other Unix file systems such as ufs or efs are going to have to devote some time to getting used to new vocabulary, commands and ways of thinking.

…

If you have ever tried to contract for hardware support for an older Sun system, you are undoubtedly aware of the fact that Sun systems eventually reach an "end of life" stage. This is the equivalent of a retirement age for computers, the date at which Sun informs customers that support for those systems is coming to an end. While the systems may still be performing extremely well, Sun maintenance will have been assigned a predictable end date.

…

The lost+found directory included in (Unix) file systems is usually empty. Only used when fsck doesn't know what to do with files that have lost their place in the file system, they stand as a temporary holding place for those rare instances in which fsck can't put everything back together after file systems have become corrupt in some way. If you see files in lost+found, you can expect them to look rather unusual. Take these files found on a Solaris 9 system after a panic and a subsequent fsck: -rw-r--r-- 1 johndoe staff 1576 Apr 22 11:26 #00805349 -rw-r--r-- 1 johndoe staff 4363 Apr 22 11:26 #00805350 -rw-r--r-- 1 johndoe staff 4566 Apr 22 11:26 #00805351 The names of these files were lost before fsck tried to piece things back together. The directory that had originally contained the salvaged files was, for some reason, not recoverable. And, since filenames are stored in directory files and nowhere else on ufs file systems, what we are able to recover for these files are the various pieces of information stored in the files' inodes — the owners, groups, access permissions and pointers to the files' contents.

…

Want to do something with those crash dump files other than remove them? Want to extract some useful information without a lot of work? Take a look at Sun's free crash analysis tool, scat.

…

When tracking down an unusual problem on a Unix system, you may encounter many turns and dead ends on the path toward the solution as some problems may have little connection to what first appears to be troubling your system. We're going to follow an unusually winding path from first appearance of a problem to its eventual solution.

With nearly 9,000 file extensions listed and 50 users browsing the site on a Saturday night, the Dot What!? claims to be the net's #1 file extension website. It offers visitors an opportunity to suggest additional file extensions and to add comments concerning their uses and associations.

…

Send in your Unix questions today! See additional Unix tips and tricks While not heavily used, options available for UFS file systems can dramatically improve file system performance and stablility. In this week's column, we're going to take a look at how some of these options affect the way file systems operate and why you might consider using them.

Send in your Unix questions today! See additional Unix tips and tricks Setting up a Unix system to be an NTP client is generally straightforward. On those Unix platforms that include NTP in the default configuration, you may only need to make a few adjustments to NTP's default configuration file for the system to sync up to a reference time server(s) and keep good time. On a Solaris system, for example, this involves copying a prototype file and customizing it. You can insert the names or IP addresses of the time server(s) you have elected to use -- whether public NTP servers or NTP servers that you have set up on your local network -- or configure the system to receive broadcast time updates. Once a system has been configured, the NTP daemon will start whenever the system boots and run continuously in the background. Configuration of NTP servers, on the other hand, can be simple or complex, depending on the options that you wish to use and how well you understand the NTP service. Many Unix systems today ship with NTP software. These include Solaris, SCO, FreeBSD and Mac OS X. On some Linux systems, you will need to download and install a package, such as ntp-4.1.2-5.i386.rpm, to acquire NTP services. Once configured, the NTP service requires little or no administration. New clients will have to be configured and an occasional verification of your time sources may be warranted, but the service otherwise runs unattended. Boot-time NTP If you only want to synchronize your systems at boot time, you can configure an ntpdate command in your start scripts. This will ensure that your system starts up with a reasonable clock setting. On a Solaris system, this might be done with a script like that shown below, installed as /etc/rc2.d/S73ntpdate.

Server disks are getting larger all of the time, but this simple fact doesn't seem to be making much of a difference in the system administrator's day-to-day routine. OUr disks are still filling up faster than most of us can trim them down. So, when we just need to free up a chunk of disk space in a hurry on some particular file system, what should we do? Finding a chunk of disk space that we can potentially move from one partition to another in order to create needed space sounds easy enough, but is a relatively tedious task. There are no obvious tools or commands to identify candidate files or directories quickly and easily. Aside from tracking down core files and large temporary files (files that we can generally identify by name), there's no easy way to find a file or group of files that can be moved or removed in a pinch. Let's look at some tricks that might make the task a little easier. Finding Large Files To find large files within a particular partition, we can always use a command like this: find / -mount -type f -size +10000 -ls This command will look through the root partition (but NOT other partitions) for files larger than 5 MB or so, the 10000 in this command representing the file size in 512-byte blocks and the "+" indicating "larger than". The "mount" argument in this command keeps this find command from searching through all other mounted partitions for candidates while the "-type f" clause keeps the command from reporting on anything other than regular files. Similar commands can be constructed to find large files in other file systems. Here's one looking in /opt for files larger than half a gigabyte that has found two 1 GB files: # find /opt -mount -type f -size +1000000 -ls 177 1049096 -rw------t 1 root other 1073741824 Oct 7 16:05 /opt/swapfile 178 1049096 -rw------t 1 root other 1073741824 Oct 7 16:08 /opt/swapfile2

Send in your Unix questions today! See additional Unix tips and tricks Last week's column introduced NTP, the Network Time Protocol and the concept of highly accurate timekeeping. While numerous commands exist to help system administrators maintain fairly accurate time on the systems they manage, the most obvious are very limited. As a result, most networks suffer from large discrepancies in system time. Time differences such as those shown below (taken from an actual network) are not uncommon:

Send in your Unix questions today! See additional Unix tips and tricks For some of us, the word "synchronize" brings up memories of the characters on Mission Impossible synchronizing their watches so that they can complete a seemingly impossible mission with split-second accuracy. While time synchronization on computer systems seems far less dramatic, it is no less critical. Time differences between systems running a complex application can lead to some very troublesome problems -- such as when these time differences make transactions appear to have happened out of order. To avoid this kind of problem, a number of solutions for keeping system clocks in synch, have been devised. NTP is the larges scale and most effective of these.

Send in your Unix questions today! See additional Unix tips and tricks People who have had bad experiences on Windows disks that performed poorly after they had become very fragmented often wonder if they need to apply some kind of periodic analysis and defragmentation on their Unix systems as they transition into a Unix admin or user role. For the most part, the answer is no. Most Unix file systems don't become fragmented the way FAT and NTFS file systems do. But, rather than give a quick yes/no answer, let's take a look at what fragmentation, and why Unix file systems are not as prone to fragmentation as their Windows cousins and what you need to do when a Unix file system is fragmented.

If you have tried to give away any files lately on any of your Unix systems (i.e., without first becoming root), you may have been surprised to learn that you can't. On most Unix systems today, any non-root user is likely to get errors such as these when he or she tries to change ownership on a file: $ chown sbob *ksh chown: acc_cfg.ksh: Not owner chown: checkout.ksh: Not owner The error message "Not owner" doesn't necessarily mean what it says. You may be the owner of the file(s) in question and still not be able to change the owner to some other user.

For many of us, this inability to give away our files contradicts what we remember from our early days with Unix. We may even scratch our heads and mutter "Wait! I used to be able to do this!". So, let's take a look at when chown works, why it only works sometimes and what kind of control we have over how the chown command operates.

…