情况: Git 远程服务器 (例如 GitLab 实例) 位于内网, 需要能从外部访问.
Situation: Git remote server (e.g. GitLab instance) is in private network but need to access from outside.
一种解决方案: 用 ssh 打开隧道, 例如
One solution: open tunnel using ssh, like
Host jumper-machine
# ...
LocalForward 3002 10.1.2.233:80
LocalForward 3003 10.1.2.233:33322
在用 ssh jumper-machine 开启隧道后,
即可使用 http://localhost:3002 访问 Git 远程服务器的网页,
ssh://git@127.0.0.1:3003/<user>/<repo> 可作为 Git 仓库的远程地址.
After opening tunnel using ssh jumper-machine,
use http://localhost:3002 to visit webpage of Git remote server,
use ssh://git@127.0.0.1:3003/<user>/<repo> as Git remote url.
When processing continuous observation of more than 1 day,
an error occurred from DSPSR:
Error::message
epoch 60230.28412758417979894210 not spanned by ChebyModelSet
The error is related to TEMPO2 wrapper T2Predictor, where TEMPO2 complains ChebyModelSet_OutOfRange.
This points to the command line of DSPSR calling TEMPO2, which does have a span of one day:
tempo2 -npsr 1 -f pulsar.par -pred "fast 60229.283869345 60230.283869345 200.006942749023438 350.006942749023438 12 2 3599.9999999999998" > stdout.txt 2> stderr.txt
Further searching shows the time span comes from dspsr/Signal/Pulsar/Fold.C, line 243.
Changed this magic number
diff --git a/Signal/Pulsar/Fold.C b/Signal/Pulsar/Fold.C
index 009c1615..0c5c42f9 100644
--- a/Signal/Pulsar/Fold.C
+++ b/Signal/Pulsar/Fold.C
@@ -262,7 +262,7 @@ dsp::Fold::get_folding_predictor (const Pulsar::Parameters* params,
/*
* Tempo2 predictor code:
*
* Here we make a predictor valid for the next 24 hours
* I consider this to be a bit of a hack, since theoreticaly
* observations could be longer, and it's a bit silly to make
* such a polyco for a 10 min obs.
*
*/
- MJD endtime = time + 86400;
+ MJD endtime = time + 10*86400;
generator->set_site( observation->get_telescope() );
generator->set_parameters( params );
generator->set_time_span( time, endtime );
so folding can be done further.
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Translation below.
问题描述
某 2021 年还安装 CentOS 7 的服务器近期时常出现无响应、远程无法连接, 键鼠输入有延迟, 且有内核出错记录:
Aug 11 12:45:31 <machine name> kernel: warn alloc falled: 1380491 callbacks suppressed
Aug 11 12:45:31 <machine name> kernel: swapper/27: page allocation failure: order 0, mode: 0x20
Aug 11 12:45:31 <machine name> kernel: CPU: 27 PID: 0 Comm: swapper/27 Kdump: loaded Tainted: P OE ------------ 3.10.0-1160 62.1.el7.x86 64 #1
Aug 11 12:45:31 <machine name> kernel: Hardware name: <name>
Aug 11 12:45:31 <machine name> kernel: Call Trace:
Aug 11 12:45:31 <machine name> kernel: <IRQ> [<ffffffffbcb865a9>] dump_stack+0x19/0x1b
Aug 11 12:45:31 <machine name> kernel: [<ffffffffbc5c4bd0>] warn alloc failed+0x110/0x180
Aug 11 12:45:31 <machine name> kernel: [<ffffffffbc4d3383>] ? __wake up+0x13/0x20
Aug 11 12:45:31 <machine name> kernel: [<ffffffffbc5c976f>] __alloc_pages_nodemask+0x9df/oxbe0
Aug 11 12:45:31 <machine name> kernel: [<ffffffffbc5c9b78>] page_frag_alloc+0x158/0x170
Aug 11 12:45:31 <machine name> kernel: [<ffffffffbca4808d>] __napi_alloc_skb+0x8d/0xe0
Aug 11 12:45:31 <machine name> kernel: [<ffffffffc03df895>] mlx5e_skb_from_cqe_mpwrq_nonlinear+0x65/0x2f0 [mlx5_core]
Aug 11 12:45:31 <machine name> kernel: [<ffffffffc03dfdbf>] mlx5e_handle_rx_cqe_mpwrq+0xbf/0x8c0 [mlx5_core]
Aug 11 12:45:31 <machine name> kernel: swapper/57: page allocation failure: order 0, mode: 0x20
Aug 11 12:45:31 <machine name> kernel: CPU: 57 PID: 0 Comm: swapper/57 Kdump: loaded Tainted: P OE ------------ 3.10.0-1160 62.1.el7.x86 64 #1
Aug 11 12:45:31 <machine name> kernel: Hardware name: <name>
Aug 11 12:45:31 <machine name> kernel: Call Trace:
Aug 11 12:45:31 <machine name> kernel: <IRQ> [<ffffffffbcb865a9>] dump_stack+0x19/0x1b
Aug 11 12:45:31 <machine name> kernel: [<ffffffffc03e14be>] mlx5e_napi_poll+0xbe/0xd10 [mlx5_core]
Aug 11 12:45:31 <machine name> kernel: [<ffffffffbc78da24>] ? __radix_tree_lookup+0x84/0xf0
......
重启后可恢复一段时间, 但数小时到数天后仍会卡死.
问题排查
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When testing SYCL programs on some backend based on Clang 14, it is noticed that the gdb-9 bundled with Ubuntu 20.04 cannot correctly read debug info of binary produced by clang-14, then stack info is not available at all.
Although haven’t figured out why, compiling & installing a gdb-13 simply fixes this problem.
NOTE: tested with vendor-specific compiler based on clang-14, not sure if applicable to vanilla Clang.
Strange things happened when debugging the new pipeline structure of simple-radio-telescope-backend: when emulated_fp64 is switched on (that is, the df64 type in “Emulated double precision Double single routine header” by StickGuy, Norbert Juffa, Reimar, et al. is used), under Debug configuration every thing works fine, but Release configuration gives wrong results!
An example is evaluating phase delay of radio wave in plasma caused by electrodynamics, the difference of cos() and sin() of such phase evaluated using float64 and df64 is shown below:
Difference of result given by df64 & double under Debug configuration, tested on NVIDIA RTX A4000
Difference of result given by df64 & double under Release configuration, tested on NVIDIA RTX A4000
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Credit: Chenchen Miao and Cijie Zhang
1. 利用 HPE 的 iLO 功能实现远程操作服务器 / operate the server remotely using HPE’s iLO
- 记下机箱标签上的 iLO 账号与密码 / remember username and password of iLO which is on the label of server
- 第一次启动需要接上屏幕, 在引导阶段会显示 iLO 的 IP 地址 / screen seems required on first boot, IP address of iLO will show when booting
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TL;DR: this is a stack overflow caused by large array on stack, so enlarge stack size using ulimit -s <stack size in KB>
Incident
An error occurred when processing raw baseband data of a radio telescope using dspsr:
$ dspsr -b 4194304 -D 56.716 -A -L 1.073741824 -c 1.073741824 -O ${file}_128 -e rf -F 128:D ${file}.bin -U 4096
Only single polarization detection available
dspsr: Single archive with multiple sub-integrations
dspsr: dedispersion filter length=131072 (minimum=8192) complex samples
dspsr: 128 channel dedispersing filterbank requires 33554432 samples
dspsr: blocksize=330382096 samples or 4096 MB
dsp::Fold::choose_nbin WARNING Requested nbin=4194304 > sensible nbin=2097152. Where:
sampling period = 0.000256 ms and
requested bin width = 0.000256 ms
dsp::Archiver::finish archive '13835058401541322426_128.rf' with 1 integrations
62305 Segmentation Fault (Core dumped)
Analyze
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Update: seems fixed on Linux kernel 6.0.9 / 6.1, commit 1598bfa “platform/x86: hp_wmi: Fix rfkill causing soft blocked wifi”
TL;DR The temporary fix is either blacklist the kernel module hp_wmi currently, or comment out codes that provides rfkill function in that module.
Recently Windows auto-updated the BIOS of my laptop HP Elitebook 865 G9 to (U82) 01.02.01 Rev.A,
then in Linux the wifi and bluetooth device keeps on and off, seems 1-2 time(s) per second,
and character ^@ of unknown source keeps being inputed, even in emergency mode
(which make it almost impossible to type in password for root, thus cannot access root shell.)
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