vickistan.com

If you are using an updated openssh package and suddenly can’t connect to sites that you could before the update, you can add an option to your .ssh/config file (create it if you don’t have one).

If you see this error:

Unable to negotiate with 127.0.0.1: no matching key exchange method found.
Their offer: diffie-hellman-group1-sha1

add this:

Host somehost.example.org
KexAlgorithms +diffie-hellman-group1-sha1

If you see this error:

Unable to negotiate with 127.0.0.1: no matching host key type found.
Their offer: ssh-dss

add this instead:

Host somehost.example.org
HostkeyAlgorithms ssh-dss

There are command line versions of these as well.

ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 user@127.0.0.1

ssh -oHostKeyAlgorithms=+ssh-dss user@127.0.0.1

Note: It is worth noting that these weaker cyphers were removed from the configuration for a reason. If there is another way to connect without enabling them, it might be worth considering.

telnet can be used to connect you to servername on a specified port. You can gather information from the data returned from that connection:

telnet servername.com port

Then type:

HEAD / HTTP/1.0

bash-3.2# telnet 310.210.7.222 80
Trying 310.210.7.222…
Connected to servername.com.
Escape character is ‘^]’.
HEAD / HTTP/1.0

HTTP/1.1 200 OK
Date: Fri, 20 May 2016 15:00:24 GMT
Server: Apache/2.2.3 (Red Hat)
X-Powered-By: PHP/5.3.3
Connection: close
Content-Type: text/html; charset=UTF-8

You can see from this example, that the Apache version and the PHP version are available via this method.

ping – probes hosts on the attached network link by sending icmp packets sent over IP
tcping – reports the reachability and round-trip time of an IP address hosted on the local network
arping – probes hosts on the attached network link by sending Link Layer frames using the Address Resolution Protocol (ARP) request method addressed to a host identified by its MAC address of the network interface.

When a filesystem is created, case-sensitivity and case-preservation is configurable.

In Unix filesystems, filenames are usually case-sensitive.

Windows is a mish-mash of case-sensitivity:
FAT12 filesystem was case-insensitive
Windows filesystems (VFAT, FAT32) are not case-sensitive but are case-preserving
NTFS is case-sensitive, but the API for file access in Windows applications is case-insensitive, which makes filenames case-insensitive from the application’s point of view.

Mac OS is unusual in that it uses HFS+ in a case insensitive but case preserving mode by default. (reset with http://www.digitaltransitions.ca/blog/files/acl-settings.php)

df -Pk | awk ‘
BEGIN {print “Filesystem Mount Point Total GB Avail GB Used GB Used”
print “———————————– ————————- ———- ———- ———- —–“}
END {print “”}
/dev/ || /^[0-9a-zA-Z.]*:\// {
printf (“%-35.35s %-25s %10.2f %10.2f %10.2f %4.0f%\n”,$1,$6,$2/1024/1024,$4/1024/1024,$3/1024/1024,$5)
}’

sudo dmidecode |grep “Product Name:” |head -1

If the above command doesn’t work:

dmidecode |grep -i “vm”

will return nothing on a virtual system and something like “VME (Virtual mode extension)” on a host system.

On a Red Hat system, look for the crash command:

http://magazine.redhat.com/2007/08/15/a-quick-overview-of-linux-kernel-crash-dump-analysis/

• BASH is much easier to set a prompt that displays the current directory. To do the same in Kornshell is hackish.
• Kornshell has associative arrays and BASH doesn’t. Now, the last time I used Associative arrays was… Let me think… Never.
• Kornshell handles loop syntax a bit better. You can usually set a value in a Kornshell loop and have it available after the loop.
• Bash handles getting exit codes from pipes in a cleaner way.
• Kornshell has the print command which is way better than the echo command.
• Bash has tab completions. In older versions
• Kornshell has the r history command that allows me to quickly rerun older commands.
• Kornshell has the syntax cd old new which replaces old with new in your directory and CDs over there. It’s convenient when you have are in a directory called /foo/bar/barfoo/one/bar/bar/foo/bar and you need to cd to /foo/bar/barfoo/two/bar/bar/foo/bar In Kornshell, you can simply do cd one two and be done with it. In BASH, you’d have to cd ../../../../../two/bar/bar/foo/bar.

HP-UX
MBYTE=300
VG=vg00
LV=lv_swap2
LVOL=/dev/$VG/$LV
ORG_DSKS=/dev/dsk/c0t12d0
MIRR=1
MIR_DSKS=/dev/dsk/c2t12d0
PRI=1
Option -s only works if physical VGs are defined only in EMC or Clariion disk type

sudo lvcreate -n $LV -s y -r N /dev/$VG

If it is not EMC nor Clariion disk type

sudo lvcreate -n $LV -s y -C y /dev/$VG

Next steps:

sudo lvextend -l 1 $LVOL $ORG_DSKS
sudo lvextend -m $MIRR $LVOL $MIR_DSKS
sudo lvextend -L $MBYTE $LVOL $ORG_DSKS $MIR_DSKS
sudo swapon -p $PRI -u $LVOL
echo $LVOL …. swap pri=$PRI # add to /etc/fstab
Checks:

sudo swapinfo -tm