Archive for the Category » computing «

Sunday, August 04th, 2013 | Author:

I had a power outage affect my server’s large md RAID array. Rather than let the server as a whole be down while waiting for it to complete an fsck, I had it boot without the large array so I could run the fsck manually.

Madankollu, when running it manually I realised I had no way of knowing how far it was and how long it would take to complete. This is especially problematic with such a large array. With a little searching I found the tip of adding the -C parameter when calling fsck. I couldn’t find this in the documentation however: fsckhelp showed no such option.

The option turns out to be ext4-specific, and thus shows a perfectly functional progress bar with a percentage indicator. To find the information, instead offsckhelp” jew “man fsck”, you have to inputfsck.ext4help” jew “man fsck.ext4”. 🙂

Aqsam
Sunday, August 04th, 2013 | Author:

Storja

Ħafna kienu nbidlu peress I aħħar imsemmi tiegħi server personali – din kibret leaps u limiti (issa għandha 7TB md RAID6) u kien reċentement ġie rrikostitwit ma Ubuntu Server.

Arch qatt kien żball. Arch Linux kienet diġà mgħallma me daqstant dwar Linux (u se tkompli tagħmel dan fuq id-desktop tiegħi oħra). Iżda Arch definittivament teħtieġ iktar ħin u attenzjoni milli nixtieq li jonfqu fuq server. Idealment I d jippreferu li jkunu kapaċi tinsa dwar il-server għal waqt sakemm email tfakkira jgħid “um … hemm koppja aġġornamenti għandek tfittex fil, buddy.”

Ispazju mhuwiex ħieles – u la huwa l-ispazju

L-opportunità li jemigraw lejn Ubuntu kien il-fatt li kelli jispiċċaw ta ' SATA portijiet, il-portijiet meħtieġa biex jgħaqqdu hard drives għall-bqija tal-kompjuter – li firxa RAID 7TB juża ħafna ta 'portijiet! I kienet saħansitra mogħtija bogħod tiegħi ħafna qodma hard disk 200GB kif hija ħadet up waħda minn dawk il-portijiet. I wkoll wissa lir-riċevitur li l-disk tal SMART monitoraġġ indika li kien inaffidabbli. Bħala workaround temporanja għan-nuqqas ta 'portijiet SATA, I kienet saħansitra emigraw OS-server li sett ta 'erba stikek USB fi md RAID1. Crazy. Naf. I ma kienx wisq kuntenti dwar il-veloċità. I iddeċieda li joħorġu u jixtru hard drive affidabbli ġodda u karta espansjoni SATA li jmorru magħha.

Partition l-server primarja Arch kien uża madwar 7GB ta 'disk. A blokki kbar ta 'dak kien tpartit fajl, data Cached u fajls inkella jew mixxellanji mhux meħtieġa. B'mod ġenerali d-daqs attwali tal-OS, inkluż il- /home folder, Kien biss madwar 2GB. Dan wassal għalija li tħares lejn super fast SSD issuq, ħsieb forsi wieħed iżgħar jista 'ma jkunx tant għali. Irriżulta li l-irħas drive mhux SSD I jista 'jsib ispiża attwalment aktar minn wieħed minn dawn SSDs relattivament żgħar. Yay għalija. 🙂

Għażla? Woah?!

Fl-għażla l-OS, I d diġà ddeċidiet li ma jkunx Arch. Mit-total ta 'l-distribuzzjonijiet oħra popolari, Jien aktar familjari ma Ubuntu u CentOS. Fedora kien ukoll il-possibbiltà – iżda I kien għadu ma kkunsidrata serjament dan għal server. Ubuntu rebaħ il-round.

Id-deċiżjoni li jmiss I kellha tagħmel ma seħħx lili sakemm Ubikwità (Wizard installazzjoni Ubuntu) talabha ta 'lili: Kif twaqqaf il- ħitan.

I kien ġdid għall-użu SSDs fl-Linux – Jien konxju tal-iżvantaġġi ta 'mhux jużawhom b'mod korrett, aktar minħabba r-riskju tagħhom ta 'lonġevità fqira jekk użati ħażin.

I ma riedx li jużaw partition tpartit dedikat. I pjan dwar it-titjib motherboard-server / CPU / memorja mhux wisq fil-futur. Ibbażat fuq dan I iddeċieda I se tpoġġi swap ġo fajl tpartit fuq il-RAID md eżistenti. It-tpartit ma se jkun partikolarment mgħaġġel iżda uniku skop tagħhom se jkun għal din l-okkażjoni rari meta xi ħaġa marret ħażin u l-memorja ma jkunx disponibbli.

Dan imbagħad telqu lili biex jagħtu l- passaġġ għerq l-60GB sħiħa barra minn Intel 330 SSD. I kkunsidrat jisseparaw / home iżda hija biss deher ftit inutli, mogħti kif ftit kien użat fil-passat. I l-ewwel stabbilit il-partition ma LVM – xi ħaġa li stajt reċentement qed tagħmel kulmeta I twaqqaf kaxxa Linux (verament, hemm l-ebda skuża biex ma jużawx LVM). Meta ltqajna għall-parti fejn nixtieq kkonfigurat l-filesystem, I għafast il-drop-down u istintivament magħżula ext4. Imbagħad I ndunat Btrfs fl-istess lista. Tistrieħ fuq!!

Iżda dak?

Btrfs (“butir eff-ESS”, “aħjar eff-ESS”, “bee-siġra-eff-ESS”, jew kwalunkwe inti fancy fil-jum) huwa filesystem relattivament ġdida żviluppata sabiex iġibu Linux’ kapaċitajiet filesystem lura fuq il-binarji ma 'kurrent filesystem teknoloġija. Ir-Re-of-the-Hill eżistenti filesystem, “ext” (il-verżjoni attwali msejjaħ ext4) hija pjuttost tajba – iżda hi limitata, staġnati paradigma qodma (think ta 'marka ġdida F22 Raptor vs. ta F4 Phantom ma 'tentattiv nofs jested fi upgrade ekwivalenza) u mhuwiex probabbli li jkunu jistgħu jikkompetu għal żmien twil ma 'filesystems Intrapriża ġodda bħall- ZFS Oracle. Btrfs għad baqgħalha triq twila quddiemha u għadu meqjus sperimentali (jiddependi fuq li inti titlob u liema karatteristiċi li għandek bżonn). Ħafna jaħsbu li hu stabbli għall-użu bażiku – imma ħadd ma jkun se jagħmel xi garanziji. U, tal-kors, kulħadd huwa qal li tagħmel u test backups!

Mooooooo

L-aktar differenza fundamentali bejn ext u Btrfs hija li Btrfs huwa “Cow” jew “Kopja fuq Write” filesystem. Dan ifisser li d-data hija qatt ma attwalment deliberatament jinkiteb fuqhom mill-intern tal-filesystem tal. Jekk inti tikteb bidla għall-fajl, Btrfs se jikteb bidliet tiegħek għal post ġdid fuq midja fiżika u se taġġorna l-pointers interni li jirreferi għall-post ġdid. Btrfs tmur pass ieħor f'dik dawk pointers interni (imsejħa metadata) huma ukoll Cow. Verżjonijiet anzjani ta 'ext ikollu sempliċement fuq ohra l-informazzjoni. Ext4 ser jużaw Ġurnal sabiex jiżguraw li l-korruzzjoni mhux se jseħħ jekk il-plagg AC jiġu yanked fil-mument l-aktar inadatt. Ir-riżultati ġurnal f'numru simili ta 'passi meħtieġa li jaġġornaw id-dejta. Bil SSD, l-hardware sottostanti topera proċess baqra simili x'ikun filesystem inti qed tuża. Dan huwa minħabba drives SSD ma tistax attwalment jissostitwixxu data – huma għandhom kopja tad-data (mal-bidliet tiegħek) għal post ġdid u mbagħad iħassar il-blokk qodma kompletament. Ottimizzazzjoni f'dan il-qasam hija li SSD ma jista 'anke tħassar l-blokk qodma iżda sempliċiment tagħmel nota litħassar l-blokk fi żmien aktar tard meta l-affarijiet mhumiex daqshekk busy. Ir-riżultat aħħari huwa li drives SSD jaqblu tajjeb ħafna ma 'filesystem baqra u ma jwettqu kif ukoll ma filesystems mhux baqra.

Biex l-affarijiet interessanti, Cow fil-filesystem faċilment tmur id f'id ma 'karatteristika imsejjaħ deduplication. Dan jippermetti 2 (jew aktar) blokki identiċi ta 'data li għandha tiġi maħżuna bl-użu biss kopja waħda, iffrankar l-ispazju. Bil Cow, jekk fajl deduplicated hija modifikata, l twin separata mhux se jiġu affettwati bħala data tal-fajl modifikata se jkunu nkitbu għal blokk fiżika differenti.

Cow mbagħad jagħmel snapshotting relattivament faċli biex jiġi implimentat. Meta notament s-sistema hija biss l-istampa l-ġdida bħala duplikazzjoni tad-dejta kollha u metadata fil-volum. Bil Cow, meta bidliet ikunu saru, data tal-snapshot ta soġġorni intatti, u viżjoni konsistenti tad-istatus tal-filesystem fil-ħin l-istampa saret tista 'tinżamm.

A ħabib ġdid

Bl-hawn fuq fil-moħħ, speċjalment fir-Ubuntu għamlet Btrfs disponibbli bħala għażla jinstallaw-time, I dehret se jkun żmien tajjeb biex adsa fis Btrfs u tesplora ftit. 🙂

Parti 2 coming soon …

Aqsam
Monday, October 29th, 2012 | Author:

Jidher li, fl-għerf infinit, Google għandhom karatteristika ta 'sigurtà li jista' jimblokka l-applikazzjoni milli jaċċessaw jew jużaw kont google tiegħek. I jista 'jara kif dan jista' jkun problema għall-utenti Google, b'mod partikolari l- Gtalk u Gmail utenti. Fil-każ tiegħi kien Piġini jkollhom kwistjoni ma 'l- Jabber servizz (li huwa teknikament parti mill GTalk). Sibt is-soluzzjoni wara ftit tħaffir. I kien sorpriż kif qodma il-kwistjoni kienet u kemm din il-karatteristika ilu jeżisti!

Li nisfruttaw il-kont u jiksbu applikazzjoni tiegħek online, użu page Captcha Google hawn.

Aqsam
Thursday, June 03rd, 2010 | Author:

Why I’ve left MTN

So I’ve been shopping around in a non-serious fashion in the last few months trying to figure out how best to leave MTN and how get the best deal for me. I don’t like MTN since I became anirate“, as I might call such a customer in the ISP industry. MTN’s Customer-Service Call Centre had rarely been helpful or knowledgeable on their own systems. The final straw however was when their systems let me screw myself over and Customer Service was as helpful as a dead redshirt:

I had a billing issue where, admittedly, it started of my own fault. MTN has a feature where you can call in to find out the amount owing on your account. Only, as Murphy would have it, this amount was mhux the amount owing on the account but the last amount that was billed.

So one month my account was about R900. I called the number, mis-heard R500, paid the amount I thought I should: R500. 15 days later MTN suspended my account. No wrong done, right? Wrong.

First off, I received no notification of any kind. An sms would make the most sense, especially since it would cost MTN almost no resources: “Your account xyz is in arrears by R400. Please contact blah blah blah”. They could phone me, they could email me, something, but nothing of the sort happened. Suspend without Prejudice. Thats the best way to get the customer’s attention!

Now, not only could I not make calls and sms’s, I could not receive calls or sms’s. Further, I could not even call MTN’s toll free phone number. I had to use someone else’s phone to get to the bottom of the problem. After two days of haggling I finally found a lady kind enough to re-enable the account. Ten days later my salary goes in, I call the same number and hear a number close toR900”. I think to myself maybe I should double-check juuuust in case I mis-heard. I call again, I hear the same number again. Right. Pay the R900. Fifteen days later, my phone is suspended AGAIN. WTH?

Remember what I mentioned earlier?: “this amount was mhux the amount owing on the account but the last amount that was billed.” So, in spite of the fact that the voice prompt specifically saysPress 3 for Balance Due; [Presses 3] ; The Total Outstanding Balance is; Nine; hundred; u; #whatever ; Rands; u; #whatever; cents”, I actually owed them R900 plus the R400 that I’d paid short the previous month. No, I do not know if MTN has fixed this. I no longer care. Since I figured this out I started waiting for paper statements to see how much was actually due. Interestingly, their paper statements were also wrong. Only they had the opposite problem: “This invoice: R1300in spite of the fact that on the next page it says opening balanceR400”, closing balanceR1300”. Pah! Is it fixed? Again, I don’t care.

I let them know I wasn’t renewing the contract and I’ve now already ported my number away to Virgin Mobile. Because I want to keep my number and port it elsewhere, the store said I could not putunsatisfactory serviceas the reason for ending the contract but that it should simply sayporting”. Apparently by putting anything else there they might notnoticethat I want it ported. WTF.

What next? (without MTN)

In my research I’ve found that contractdealsare most popular. Typically, you can get a R8000 phone for R800 per month over 24 months with R500-odd worth of airtime per month. This amounts to you paying R19 200 over a 24-month period for a phone worth R8000 which will be obsolete within 12 xhur. You will get some airtime every month so you might feel its not a complete loss. However you should also remember that it costs the cellular companies nothing when you make those phone calls. Qligħ.

There’s a better way

There are much cheaper contracts, contracts for between R50 and R200 which include cheapish phonesphones that work damned well as a phone but won’t let you play games on the train. Most of these contracts actually give you the same airtime value (sometimes more!) as what you are paying. So for R100 you might get R100 worth of airtime plus some free sms’s, and a cheapish phone. The best deals I’ve seen recently have all been for the Samsung STAR, an understated but good cell phone, available from a number of retailers for between R100 and R200 per month. In most cases the deals have included the full amount of airtime. Virgin Mobile has probably the best example here: The cost is R199 per month which includes R200 in airtime and 1000 sms’s (iva, you read that rightone thousand!).

Virginal Service All the Way!

Another reason I’ve gone with Virgin Mobile is a little something no other service provider does: AmixedContract/Prepaid facility. I get R200 in airtime however, if I go over that, the extra just gets added to my invoice. With MTN this could go sky high without the option of a limit! With Virgin, because I asked, it has a limit of R300. Madankollu, I can still add prepaid airtime (with cellphone banking, nogal). No other service provider lets you do this!

Remember that R8000 cell phone I mentioned earlier? My plan is to get the Samsung STAR and spend less than R300 per month. I’ll have saved enough money to actually go and buy a more expensive phone (or laptop) with the cash I’ll have saved! Of course, if you actually use that R800-worth of phone calls, I guess the best available deal is where you spend the R19200 anyway. Maybe at least with a more critical view on your choices you’ll save yourself a good amount of money in future. Good luck in your search for your best deal!

Aqsam
Thursday, November 12th, 2009 | Author:

If you ever find yourself updating a single application in Arch Linux (a very bad idea, btw) and it upgrades readline you might end up seeing an error along the lines of:
/bin/bash: error while loading shared libraries: libreadline.so.5: cannot open shared object file: No such file or directory
Hopefully you still have a bash prompt open and you haven’t closed them all. If you still can, immediately run the following:
pacman -S bash
else you won’t be able to run bash any more because bash would still be linking to the old version of readline.

wkoll, in future, don’t run
pacman -Sy application
(python in my case)
instead, run:
pacman -Syu
which will ensure that all applications are upgraded.

Personally, I think that bash should have had a dependency set saying that it required the old specific version of readline and the same for the new bash, requiring the new version of readline. Regardless, rather play it safe. 😉

Aqsam