System information

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There are several ways to gather system information. It is a good idea to keep abreast of your machine's utilization and capacities.

General System Information Tools/Utilities

  • cat /var/log/messages -- is the same as dmesg
  • dmesg -- kernel messages given during booting.
  • kinfocenter -- good overview
  • tail -f /var/log/messages -- show the last couple of lines and keep outputting new lines
  • uname -a -- brief OS and kernel information.

Memory Diagnostic Tools/Utilities

  • cat /proc/meminfo -- static information about your RAM
  • ksysguard -- real-time RAM and CPU utilization printout and process table
  • top -- real-time RAM and CPU utilization printout
  • free -- current memory/swap utilization.

CPU Diagnostic Tools/Utilities

  • hwinfo --cpu -- static information about your CPU

Disk and File System Diagnostic Tools/Utilities

  • cat /etc/fstab -- show configuration file for file system mounting.
  • df -h -- current disk space usage ("-h" gives human-readable output)
  • du -h -- determine how much disk space is being used by Cwd, or any directory you specify after the du command (as in df, the "-h" means human-readable)
  • fdisk -l [/dev/hda] -- show partition table(s), leave off device name to list all
  • mount or cat /etc/mtab -- show currently mounted file systems.

Local Devices Diagnostic Tools/Utilities

  • dmidecode -- get all bios information, e.g. computer type.
  • hwinfo --pci -- list devices on the pci bus.
  • hwinfo --scsi -- list all scsi devices.
  • hwinfo --usb -- list all usb devices.
  • lsdev -- list all installed hardware.
  • lspci -- list devices on the pci bus.
  • lsscsi -- list all scsi devices.
  • lsusb -- list all usb devices.
  • setserial -bg /dev/ttyS[0-9]* -- list all active serial devices(/dev/ttyS*).

Kernel and Kernel Module Diagnostic Tools/Utilities

  • lsmod -- list kernel modules currently loaded.

Network Diagnostic Tools/Utilities

  • Directory /proc/net/
    • File arp: arp cache. Maps IP address to MAC address
    • File dev: byte and packet statistics on a per device basis.
    • File netstat: various statistics
    • File tcp: established connections.
  • Directory /proc/sys/net/ipv4/
    • File: ip_forward: read/write. Whether or not the kernal will forward IP packets from one interface to another. This is turned on if you want the machine to work as a router or a firewall.
  • ethtool $interface -- show the card's speed, capabilities and if a link is detected
  • hwinfo --netcard -- show the module name, driver activation command, network card name etc.
  • ifconfig -a -- show all current network interface information
  • ifconfig $interface -- show the information for $interface (usually something like ifconfig eth0)
  • ping $host -- use ping to determine if $host is alive on the network (for troubleshooting your local machine $host can equal "" or "localhost"
  • route -n -- show routing table, using numerical addresses.

If you want to set up a proxy firewall, this should be off, as it will be the application that forwards traffic, not the kernel.

  • File: ip_local_port_range: read/write. The range of ports that are used as source ports for outgoing connections.
  • File: tcp_sack: read/write. Whether or not TCP connections use selective acknowledgement. One=yes, zero=no.
  • File: tcp_timestamps: read/write. Whether or not TCP connections add timestamps to their connections. One=yes, zero=no.

Dynamic information

Or: What does my hardware do?

  • xosview -- CPU, network load etc. to get an overview
  • ksysguard -- CPU, network load etc. comprehensively
  • vmstat -- CPU load, swapping and I/O
  • top -- top CPU consuming processes
  • lm-sensors -- read CPU temperature etc.
  • ethereal -- a network sniffer
  • iptraf -- show network packets by size, interface etc.
  • netstAt -- show established and listening network connections
  • iostAt -- show count of read blocks in a given time etc.
  • blktRace -- sniff scsi commands etc.

X-Windows Troubleshooting Tools/Utilities

  • cat /var/log/XFree86.0.log -- print out the XFree86 error log.
    • Note that some systems do not store this log in /var/log. Use either locate XFree86.0.log or find / -name XFree86.0.log to find it.
  • glxinfo -- show the status of your OpenGL subsystem.