Juliet Kemp

As we are all (I hope …) painfully aware, decent backups are absolutely vital. Last week I looked at a potential option for offsite backup, and solutions like Bacula are excellent for providing a stable, reliable onsite backup, with historical data available. Offsite backup and historical backup have their place, and their limitations. When it […]

The /proc directory — which provides a text-based way of interfacing with system settings and processes — looks complicated at first glance, but it can be incredibly helpful when troubleshooting. Try out these tips for looking at processes: Tip of the Trade: The /proc directory provides a text-based way of interfacing with system settings and […]

The previous column looked at using /proc to examine. There’s a lot of other information available there as well. proc is fundamentally a myth: It’s a virtual filesystem, and when you ask to read a file, it talks to other bits of the kernel, retrieves the information, and hands it back as though it were […]

The superblock is the part of an ext2 or ext3 filesystem that contains the metadata — information about filesystem type, size, status and so on. Without the superblock, you’re in trouble in terms of data loss. Linux therefore has multiple copies of the superblock in different locations. Thus, even if you get a “bad superblock” […]

tcpdump is a packet sniffer — it captures the network packets (traffic) that pass through a machine, enabling you to examine and analyze the traffic afterward. It is capable of becoming very complex, but the basics are pretty straightforward and useful for network troubleshooting. Tip of the Trade: tcpdump is a packet sniffer that starts […]

The SysReq key is hidden up the top right of your keyboard, and looks a bit like a relic from a former era of computing. (Which, indeed, it is.) But there’s a bunch of things you can still do with it that may come in handy. Note that this is documented only on i386 on […]

UUID (Universal Unique Identifier) notation is another way provided by Linux to access your disks. Unlike the standard /dev/hda1, /dev/sda2 notation, it is linked specifically to a particular piece of hardware (whereas /dev/ notation can shift between disks depending on how they’re plugged in). This means you don’t have the risk of a system reconfiguration […]

… other than what its name implies. Tip of the Trade: ‘kill’ doesn’t just kill processes dead, it also can send processes a variety of other signals. kill is most often used without an argument or with -9, to kill a process off. But it can also be used to send various other signals to […]

It’s quite common to find yourself replacing machines that are still functional but just below the specs you now need — in which case it’s preferable to rehome them, rather than just throw them out. But this can have repercussions in terms of data security. Just deleting old data isn’t enough: It’s possible, if you […]

LDAP (Lightweight Directory Access Protocol) is basically a way of organizing information and providing access to it. It’s commonly used for user, service and machine information, and it’s incredibly useful. The Linux version is OpenLDAP. It will handle authentication as well as information (so the password aspect of login as well as looking up who […]

More on open source software Using PuTTY (the best Windows SSH client going) and Xming (a free X Window server for Windows) enables you to log in from a Windows box to your Unix box, and then run an X session remotely. There are other ways of doing this as well (e.g., Cygwin/X), but this […]

The tune2fs command allows you to set assorted filesystem parameters on a mounted ext2 or ext3 filesystem. The basic syntax is: Tip of the Trade: With the tune2fs command you can set assorted filesystem parameters on a mounted ext2 or ext3 filesystem. tune2fs OPTIONS device device will be something like /dev/hda1. Here are a couple […]