Locane's questions -server

Locane

Asked: 2019-04-18 13:56:17 +0800 CST

How does sar collect/calculate disk utilization %?

1

I'm pretty sure sar's disk utilization % shows how much of the disk is being utilized at any given time, but how does it calculate that? I found:

%util

Percentage of CPU time during which I/O requests were issued to the device (bandwidth utilization for the device). Device saturation occurs when this value is close to 100%.

In the sar man page, but that doesn't answer much for me - the CPU could be issuing I/O requests infinitely but that doesn't necessarily mean that the disk is at capacity - would it not be more appropriate to measure when requests start becoming latent as a ceiling for how hard a disk is being hit?

Locane

Asked: 2018-04-05 08:00:02 +0800 CST

Apache adds "./" to file names with colons in them

1

I ran in to this today running httpd on Centos 7.3. We do a lot of raw getting of apache-generated HTML docs for file download. Apparently, if a file name has a colon, apache well prepend "./" to the file name within the HTML. This tripped up our scripts:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<html>
 <head>
  <title>Index of /some_path/dir</title>
 </head>
 <body>
<h1>Index of /some_path/dir</h1>
<pre><img src="/icons/blank.gif" alt="Icon "> <a href="?C=N;O=D">Name</a>                                                                                                                                               <a href="?C=M;O=A">Last modified</a>      <a href="?C=S;O=A">Size</a>  <hr><img src="/icons/back.gif" alt="[PARENTDIR]"> <a href="/some_path">Parent Directory</a>
<img src="/icons/text.gif" alt="[TXT]"> <a href="./file1:has_colon.bios">file1:has_colon.bios</a> 2018-04-03 07:13  234K
<img src="/icons/text.gif" alt="[TXT]"> <a href="./file2:has_colon.bios">file2:has_colon.bios</a> 2018-04-03 07:13  234K
<img src="/icons/text.gif" alt="[TXT]"> <a href="file3_has_no_colon.bios">file3_has_no_colon.bios</a> 2018-04-03 07:13  234K
<hr></pre>
</body></html>

Does anyone know why this is? Is there some kind of name enforcement it's doing? And, can I turn it off?

Edit

As is pointed out below, this is due to URI naming conventions. I found the following helpful for beginning understanding: https://stackoverflow.com/questions/176264/what-is-the-difference-between-a-uri-a-url-and-a-urn

Locane

Asked: 2018-03-02 11:25:27 +0800 CST

DU shows fluctuating up then down totals during active rsync

0

I have 2 CentOS systems, one is rsyncing a ~411 gig directory to another.

On the receiving system, I typically run du -cs * |grep total;sleep 5 as a way to monitor the background rsync operation and make sure it is actually happening, since I don't know of a good way to monitor it as it runs otherwise.

The behavior I'm seeing is that du will show the total number of kilobytes go up, then go back down to a previous (and exact) value:

430235952       total
430235952       total
430235952       total
430235952       total
430235952       total
430235952       total
430235952       total
430235952       total
430498032       total <----
432333040       total <----
434430192       total <----
430235952       total <---- Back down to original value>
430235952       total
430235952       total
430235952       total
430235952       total
430235952       total
431284468       total <---- Up again
434430196       total <----
430235952       total <---- Back down again>
430235952       total
430235952       total
430235952       total
431284468       total <---- ???
434430196       total <---- ???
430235952       total 
430235952       total
430235952       total

Does anyone know what's going on here?

Locane

Asked: 2017-07-29 12:06:00 +0800 CST

PXE - LiveCD suddenly not loading for many units, works for many others?

0

I'm at a loss as to what's going wrong for me here. I have a few dozen units that work, and a few dozen units that don't, and they all vary by hardware and platform.

I have a CentOS 7.3 PXE server running cobbler with a number of CentOS-based LiveCD options on it. They worked fine up until this morning, and suddenly now we are seeing the following behavior when trying to load the vanilla CentOS LiveCD from PXE:

Hit enter
Kernel downloads
Initrd downloads, but silently (only 3 "."s show up, but I can tell its downloading watching tcpdump on the server)
The download finishes, the screen flashes, and the PXE menu comes back up
Subsequent retries result in the menu flashing and coming back up with an "invalid kernel parameter" error so briefly that I had to record it with screencap software to even see it. Additionally, only 1 packet is actually sent to the client; it's like it doesn't even attempt to download it on the second try.

The pxe menu entry for the vanilla CentOS LiveCD that looks like this:

/images/centos_livecd/centos_vmlinuz initrd=/images/centos_livecd/centos_livecd_initrd.img ksdevice=bootif lang= root=live:/centos_livecd.iso kssendmac text ks=http://10.101.24.21/cblr/svc/op/ks/profile/centos_livecd BOOTIF=<MAC>

Again - I have about 20 units of varying motherboard and platform NOT working, and about 40 or so units of varying motherboard and platform that ARE working with the exact same menu entry.

Regular installer menu entries work great - CentOS, Ubuntu, etc.

So far I've tried:

Using a vmlinuz from a CentOS install ISO
Monitoring xinetd with "watch -n 1 systemctl status xinetd" and seeing the requests come in
Monitoring tcpdump with "tcpdump -vvi |grep "

I'm at a loss, and I'm desperate. Does anyone have any ideas?

If I can gather more information using a different utility somehow on a system that is loading from PXE I would love to know how.

More information:

While tailing /var/log/messages, I noticed that the first try of loading the LiveCD appears to go swimmingly according to the network, but nothing happens on the client once the initrd.img is downloaded:

Jul 28 15:10:30 jarvis in.tftpd[12496]: RRQ from 10.101.26.176 filename /images/centos_livecd/centos_vmlinuz                                                                                      
Jul 28 15:10:30 jarvis in.tftpd[12496]: Client 10.101.26.176 finished /images/centos_livecd/centos_vmlinuz                                                                                        
Jul 28 15:10:30 jarvis in.tftpd[12501]: RRQ from 10.101.26.176 filename /images/centos_livecd/centos_livecd_initrd.img                                                                            
Jul 28 15:11:39 jarvis in.tftpd[12501]: Client 10.101.26.176 finished /images/centos_livecd/centos_livecd_initrd.img

Locane

Asked: 2017-04-27 20:17:27 +0800 CST

Redirect output to /dev/tty1 outside chroot jail?

0

I couldn't figure out exactly how to word this in my searching; if someone could tell me what this is called and point me to a resource I would greatly appreciate it.

TL;DR: For a CentOS installation, I want users to be able to watch the %post section of the kickstart file operate on the physical screen so it can be monitored. A person will hit enter on a keyboard to kick off an installation, and the same person will watch the install work on a monitor in front of them. I want them to see what it's doing.

My understanding of the structure is this:

The CentOS installation reads a kickstart file.
The %pre section of the kickstart runs in the "root" context of the installer live image.
The %post section runs in the "root" context of the installing system, allowing me to perform things like "yum -y update" etc to affect the installed system.

In a normal environment, I know I can redirect the output of a command to a terminal with:

cat "file.txt" > /dev/tty3

The problem is that this command redirects output to the chroot jail's version of /dev/tty3, which does not show on the install screen. I want it to output directly to the "parent" installation's screen, so if it somehow recognized the parent directory, it would be something like

cat "file.txt" > ../../../dev/tty3

Or something.

Can anyone help?

Locane

Asked: 2017-03-01 15:45:01 +0800 CST

Is it possible to access network resources through an EFI shell?

3

I keep seeing allusions to the idea that EFI / UEFI shells support network resources with an extension, but I don't seem to be able to find anything concrete.

I'm trying to get sas3flash.efi on to a local system from a network resource in the EFI shell.

I have an HTTP server with the files I need on it, I just need a little bit of space in the EFI shell (a ramdisk would do just fine) and the wget command.

I feel like this shouldn't be as hard as it is. Am I missing something critical?

Locane

Asked: 2016-09-23 13:49:14 +0800 CST

CentOS 7 w/Gnome hangs on boot after Nvidia driver installation?

0

there is a lot of information available on these topics separately, but I haven't been able to find an answer to what I feel is a really common situation.

I have 2 Nvidia GTX 1080s in a server with CentOS 7 and Gnome desktop. The GPUs are going to be used exclusively for CUDA calculation, not video output.

See screenshot of Kernel loading screen.

My xorg.conf looks like this:

[root@0cc47a8a1a10 ~]# cat /etc/X11/xorg.conf
# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 367.44  (buildmeister@swio-display-x86-rhel47-01)  Wed Aug 17 22:54:35 PDT 2016

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
EndSection

Section "Files"
    FontPath        "/usr/share/fonts/default/Type1"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/input/mice"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

[root@0cc47a8a1a10 ~]#

Here's the last part of /var/log/Xorg.5.log:

[    37.157] (==) ModulePath set to "/usr/lib64/xorg/modules"
[    37.157] (WW) Hotplugging is on, devices using drivers 'kbd', 'mouse' or 'vmmouse' will be disabled.
[    37.157] (WW) Disabling Keyboard0
[    37.157] (WW) Disabling Mouse0
[    37.157] (II) Loader magic: 0x7fd419fc1020
[    37.157] (II) Module ABI versions:
[    37.157]    X.Org ANSI C Emulation: 0.4
[    37.157]    X.Org Video Driver: 19.0
[    37.157]    X.Org XInput driver : 21.0
[    37.157]    X.Org Server Extension : 9.0
[    37.157] (II) xfree86: Adding drm device (/dev/dri/card1)
[    37.157] (II) xfree86: Adding drm device (/dev/dri/card2)
[    37.157] (II) xfree86: Adding drm device (/dev/dri/card0)
[    37.157] (II) xfree86: Adding drm device (/dev/dri/card3)
[    37.157] (II) xfree86: Adding drm device (/dev/dri/card4)
[    37.165] (--) PCI: (0:2:0:0) 10de:1b80:10de:119e rev 161, Mem @ 0xcf000000/16777216, 0x383fe0000000/268435456, 0x383ff0000000/33554432, I/O @ 0x00006000/128, BIOS @ 0x????????/524288
[    37.165] (--) PCI: (0:3:0:0) 10de:1b80:10de:119e rev 161, Mem @ 0xcd000000/16777216, 0x383fc0000000/268435456, 0x383fd0000000/33554432, I/O @ 0x00005000/128, BIOS @ 0x????????/524288
[    37.165] (--) PCI:*(0:6:0:0) 1a03:2000:15d9:0852 rev 48, Mem @ 0xcb000000/16777216, 0xcc000000/131072, I/O @ 0x00004000/128, BIOS @ 0x????????/131072
[    37.165] (--) PCI: (0:131:0:0) 10de:1b80:10de:119e rev 161, Mem @ 0xfa000000/16777216, 0x387fe0000000/268435456, 0x387ff0000000/33554432, I/O @ 0x0000d000/128, BIOS @ 0x????????/524288
[    37.165] (--) PCI: (0:132:0:0) 10de:1b80:10de:119e rev 161, Mem @ 0xf8000000/16777216, 0x387fc0000000/268435456, 0x387fd0000000/33554432, I/O @ 0x0000c000/128, BIOS @ 0x????????/524288
[    37.165] (II) LoadModule: "glx"
[    37.165] (II) Loading /usr/lib64/xorg/modules/extensions/libglx.so
[    37.171] (II) Module glx: vendor="NVIDIA Corporation"
[    37.171]    compiled for 4.0.2, module version = 1.0.0
[    37.171]    Module class: X.Org Server Extension
[    37.171] (II) NVIDIA GLX Module  367.44  Wed Aug 17 21:50:26 PDT 2016
[    37.171] (II) LoadModule: "nvidia"
[    37.171] (II) Loading /usr/lib64/xorg/modules/drivers/nvidia_drv.so
[    37.171] (II) Module nvidia: vendor="NVIDIA Corporation"
[    37.171]    compiled for 4.0.2, module version = 1.0.0
[    37.171]    Module class: X.Org Video Driver
[    37.171] (II) NVIDIA dlloader X Driver  367.44  Wed Aug 17 21:28:13 PDT 2016
[    37.171] (II) NVIDIA Unified Driver for all Supported NVIDIA GPUs
[    37.171] (++) using VT number 1

[    37.171] (EE) No devices detected.
[    37.171] (EE)
Fatal server error:
[    37.171] (EE) no screens found(EE)
[    37.171] (EE)
Please consult the The X.Org Foundation support
         at http://wiki.x.org
 for help.
[    37.171] (EE) Please also check the log file at "/var/log/Xorg.5.log" for additional information.
[    37.171] (EE)

Locane

Asked: 2016-07-16 15:41:01 +0800 CST

DHCP leases file has 200+ instances of the same lease?

0

I'm not sure what's going on here. I have a CentOS 7 DHCP server, and the leases file is growing at a linear but steady rate - it's re-issuing the same lease to the same MAC over and over again, and adding the new stanza to the file.

This server serves DHCP for a network of roughly 300 systems.

The DHCP config file looks like this:

ddns-update-style interim;

allow booting;
allow bootp;

ignore client-updates;
set vendorclass = option vendor-class-identifier;
one-lease-per-client true;
option pxe-system-type code 93 = unsigned integer 16;
DHCPDARGS="enp130s0f0";

subnet 10.101.24.0 netmask 255.255.252.0 {
     option routers             10.101.24.1;
     option domain-name-servers 10.101.6.62;
     option domain-search "foo.com";
     option subnet-mask         255.255.252.0;
     range dynamic-bootp        10.101.24.31 10.101.27.254;
     default-lease-time         172800;
     max-lease-time             172800;
     next-server                10.101.24.21;
     class "pxeclients" {
          match if substring (option vendor-class-identifier, 0, 9) = "PXEClient";
          if option pxe-system-type = 00:02 {
                  filename "ia64/elilo.efi";
          } else if option pxe-system-type = 00:06 {
                  filename "grub/grub-x86.efi";
          } else if option pxe-system-type = 00:07 {
                  filename "grub/grub-x86_64.efi";
          } else {
                  filename "pxelinux.0";
          }
     }
}

Is it normal behavior for dhcpd to reply to a request for a lease from the same MAC over and over and add its stanza to the end of the dhcpd.leases file, again, over and over?

Is there some setting I'm missing?

Locane

Asked: 2016-05-05 11:23:01 +0800 CST

CentOS 7 statically configured network adapter keeps getting DHCP address

2

This is driving me nuts. I have a CentOS 7 system. It is acting as DHCP for the network it is attached to, is running Cobbler and PXE, but it is not the gateway. It is the primary file server for my network.

I have an on-board network adapter configured to be static that is also the adapter that DHCP is being handed out on:

# Generated by dracut initrd
NAME="enp5s0f0"
DEVICE="enp5s0f0"
ONBOOT=yes
NM_CONTROLLED=no
#NETBOOT=yes
UUID="82b4ef5d-6c06-43f1-a0fe-7b5fcdd1fc4f"
#IPV6INIT=yes
BOOTPROTO=static
IPADDR=10.101.24.21
NETMASK=255.255.252.0
TYPE=Ethernet
GATEWAY=10.101.24.1

This adapter, about once a week, decides it wants to override the statically configured IP, and get a DHCP address. Not after booting up. Just sitting there. Operating normally. At this point, I have to physically walk to the terminal or log in with IPMI to type:

systemctl restart network

And that brings it right back to the static address. Does anyone have any idea what's going on?

Locane

Asked: 2016-03-12 15:00:35 +0800 CST

ZFS on Centos - "No such pool or dataset" and "devices is currently unavailable"

5

I'm trying to create zpools on CentOS 7 (3.10.0-327.10.1), and the zpool command seems to hate "wwn-0x" IDs.

"zpool status" is clear - there are no zpools currently configured on the machine. I have drives:

lrwxrwxrwx. 1 root root    9 Mar 11 14:30 wwn-0x5000cca2440ba0a0 -> ../../sds
lrwxrwxrwx. 1 root root    9 Mar 11 14:30 wwn-0x5000cca2440ba1dc -> ../../sdu
lrwxrwxrwx. 1 root root    9 Mar 11 14:30 wwn-0x5000cca2440992cc -> ../../sdl

If I type:

zpool create -f asdf /dev/sds /dev/sdu /dev/sdl

It works great.

If I use the WWN IDs, however, I get errors, depending on what I send it:

zpool create -f asdf wwn-0x5000cca2440ba0a0 wwn-0x5000cca2440ba1dc wwn-0x5000cca2440992cc

Yields:

cannot create 'asdf': no such pool or dataset

And typing (adding the keyword "mirror"):

zpool create -f asdf mirror wwn-0x5000cca2440ba0a0 wwn-0x5000cca2440ba1dc wwn-0x5000cca2440992cc

Yields:

cannot create 'asdf': one or more devices is currently unavailable

Specifying the full path, "/dev/disk/by-id/" + WWN, yields the same results.

This works great on Ubuntu. What's going on here? Does anyone know? Is it a bug in ZOL?

Locane

Asked: 2016-02-06 14:30:58 +0800 CST

Debian 8.3.0 - PXE installer asking for CDROM?

2

I'm sure I'm missing something easy, but I can't think of what it is.

I used Cobbler to import Debian 8.3.0, but when I attempt to install it on a machine attached to the network, the installer asks for a CDROM, fails to find it, and quits.

Does anyone know what I need to tweak in the preseed file or the kernel parameters to tell it to find its install files on a network path?

Locane

Asked: 2015-12-18 22:07:54 +0800 CST

Where does blkid get its information from? (/dev/block/ showing up in blkid output)

0

I have a CentOS 7 box that is acting very strangely. On first boot, typing "blkid" produces:

[BurnC7 (2015-12-17 22:00:25) ~]# blkid
/dev/block/8:3: UUID="c83f7479-4bc1-44e5-84ae-e38a83e75219" TYPE="ext4"
/dev/block/8:2: UUID="2a5bfdfb-2b1d-4748-96bd-fe919b132ce4" TYPE="ext4"
/dev/block/8:5: UUID="94be252f-51df-44cf-afde-57214a08d149" TYPE="swap"
[BurnC7 (2015-12-17 22:00:26) ~]#

I'm looking for a UUID -> /dev/sdX device name marriage, which is the normal output. Further puzzling, specifying a partition I KNOW exists from lsblk, typing "blkid /dev/sda2", for example, it now shows up in the regular "blkid" output:

[BurnC7 (2015-12-17 22:00:26) ~]# blkid /dev/sda2
/dev/sda2: UUID="2a5bfdfb-2b1d-4748-96bd-fe919b132ce4" TYPE="ext4"
[BurnC7 (2015-12-17 22:02:31) ~]# blkid
/dev/block/8:3: UUID="c83f7479-4bc1-44e5-84ae-e38a83e75219" TYPE="ext4"
/dev/block/8:2: UUID="2a5bfdfb-2b1d-4748-96bd-fe919b132ce4" TYPE="ext4"
/dev/block/8:5: UUID="94be252f-51df-44cf-afde-57214a08d149" TYPE="swap"
/dev/sda2: UUID="2a5bfdfb-2b1d-4748-96bd-fe919b132ce4" TYPE="ext4"
[BurnC7 (2015-12-17 22:02:33) ~]#

Even stranger STILL is that after a reboot, the blkid output now looks fine:

[BurnC7 (2015-12-17 22:04:35) ~]# blkid
/dev/sda2: UUID="2a5bfdfb-2b1d-4748-96bd-fe919b132ce4" TYPE="ext4"
/dev/sda3: UUID="c83f7479-4bc1-44e5-84ae-e38a83e75219" TYPE="ext4"
/dev/sda5: UUID="94be252f-51df-44cf-afde-57214a08d149" TYPE="swap"
[BurnC7 (2015-12-17 22:04:37) ~]#

So obviously, blkid is getting bum information from somewhere - but where?

Is there a more reliable method to get UUID -> /dev/ device name relationships?

Edit: As suggested by Michael Hampton below, "ls -l /dev/disk/by-uuid/" works, even when blkid doesn't (this is on a different unit than the examples above):

[BurnC7 (2015-12-18 12:00:40) ~]# blkid
/dev/block/8:3: UUID="ac2e5bb8-76d9-47e1-b5f7-3b91fad9e35f" TYPE="ext4"
/dev/block/8:2: UUID="6de21dfd-956d-4593-a8f2-88eeed2198f8" TYPE="ext4"
/dev/block/8:5: UUID="f6c41a22-f962-4b71-b880-54c8afb49516" TYPE="swap"
[BurnC7 (2015-12-18 12:00:41) ~]# ls -l /dev/disk/by-uuid/
total 0
lrwxrwxrwx 1 root root 10 Dec 18 11:41 6de21dfd-956d-4593-a8f2-88eeed2198f8 -> ../../sda2
lrwxrwxrwx 1 root root 10 Dec 18 11:41 ac2e5bb8-76d9-47e1-b5f7-3b91fad9e35f -> ../../sda3
lrwxrwxrwx 1 root root 10 Dec 18 11:41 f6c41a22-f962-4b71-b880-54c8afb49516 -> ../../sda5
[BurnC7 (2015-12-18 12:00:47) ~]#

Locane

Asked: 2015-02-04 11:28:32 +0800 CST

Badblocks output - Read, Write, Compare errors explanation?

3

I've been scouring the internet looking for a source on this, but have been unable to find any official documentation about Badblocks - the program that's a part of the standard e2fsprogs.

I'm using Badblocks to validate new drives that I buy, and the output always comes in:

Read errors
Write errors
Compare errors

Badblocks writes data to sectors, and then goes back and checks it to make sure that it was written properly, a test of everything involved. Compare errors pop up when the data written does not match the data read back.

My question is - what exactly is a "read error", and what exactly is a "write error"? How does Badblocks determine these failures? What thresholds are acceptable for a new drive vs. a used drive?

Locane

Asked: 2014-12-24 11:40:39 +0800 CST

Command to refresh binary paths in CentOS?

6

This is probably really easy and I just can't seem to find it.

I'm moving binaries around between /usr/bin and /usr/sbin, and even though both folders are in my $PATH, moving one binary to the other causes the system to continuously look for it in its original place.

Anyone know why this is, and if there is a command to refresh it?

Locane

Asked: 2014-06-19 10:14:03 +0800 CST

CentOS - binary won't run unless typed with absolute path

0

I'm not sure if it's a quirk of the program I'm trying to run (amidelnx) or if it's something with the way some binaries in general function. Also, I've read this question but it is not the same as what I'm experiencing.

The binary runs fine when it's "./"ed in a local directory, but if I move it to /usr/bin and attempt to just type it like a regular command it fails with "30 - Error: Problem opening file for reading.".

I can also type an absolute path to it and that works, but not if I just type the command:

/usr/bin/amidelnx               - works
cd /usr/bin;./amidelnx          - works
mv /usr/bin/amidelnx /root; cd /root; ./amidelnx  - works

mv amidelnx /usr/bin; amidelnx  - does NOT work

Any ideas?

How does sar collect/calculate disk utilization %?

Apache adds "./" to file names with colons in them

DU shows fluctuating up then down totals during active rsync

PXE - LiveCD suddenly not loading for many units, works for many others?

Redirect output to /dev/tty1 outside chroot jail?

Is it possible to access network resources through an EFI shell?

CentOS 7 w/Gnome hangs on boot after Nvidia driver installation?

DHCP leases file has 200+ instances of the same lease?

CentOS 7 statically configured network adapter keeps getting DHCP address

ZFS on Centos - "No such pool or dataset" and "devices is currently unavailable"

Debian 8.3.0 - PXE installer asking for CDROM?

Where does blkid get its information from? (/dev/block/ showing up in blkid output)

Badblocks output - Read, Write, Compare errors explanation?

Command to refresh binary paths in CentOS?

CentOS - binary won't run unless typed with absolute path

Can you pass user/pass for HTTP Basic Authentication in URL parameters?

Ping a Specific Port

Check if port is open or closed on a Linux server?

How to automate SSH login with password?

How do I tell Git for Windows where to find my private RSA key?

What's the default superuser username/password for postgres after a new install?

What port does SFTP use?

Command line to list users in a Windows Active Directory group?

What is a Pem file and how does it differ from other OpenSSL Generated Key File Formats?

How to determine if a bash variable is empty?